Page originally created in July 2011 and last updated: 19th May 2022

Inner-city Serpent  -  3.5ft adult female Aesculapian Snake at Regent's Canal, London, 2016

Aesculapian Snake  (Zamenis longissimus, previously Elaphe longissima & Coluber longissimus)

Here in the UK we have three native snake species and two introduced species of snake that have established breeding colonies at different sites. The five snake species found are:

Native:    Adder / Northern Viper (Vipera berus),     Barred Grass Snake (Natrix helvetica),     Smooth Snake (Coronella austriaca)  

Non-native:    Aesculapian Snake (Zamenis longissimus),    Eastern Romanian Grass Snake (Natrix natrix persa)

The fourth snake is the introduced Aesculapian Rat Snake. Aesculapian Snakes are originally from mainland Europe, and are found in three specific parts of the UK. Aesculapian Snakes haven't been residents in the UK for over 10.000 years, and are now considered by Natural England to be non-native to the UK. However, there are two well established breeding colonies of Aesculapian Snakes here in Great Britain that have been in existence now for over 35 years and one newer colony, only recently reported (1st June 2020), that is estimated to have been around for 15-20 years. One colony is in Central London, England and the other two colonies are both in Wales. The oldest population of Aesculapian Snakes in the UK is in Colwyn Bay, North Wales and the newest is in Bridgend, South Wales. Outside of the UK the nearest populations of wild and native Aesculapian Snakes are found in NW France.

These long slender Rat Snakes, of the Colubridae family, are Old World Snakes and are one of Europe's longest snakes. They regularly grow to a length of 140-160cm. In warmer parts of Europe they can reach up to 180cm and have even reached 225cm on one occasion. This easily makes them the longest snake found in the UK, and one of the longest in Europe. The maximum weight for males is usually around 890 grams and 550 grams for females. These snakes are usually found across southern, central and eastern Europe and prefer the same method of incubating their eggs as our native Grass Snakes, using warm damp moist areas of rotting vegetation such as hay piles and compost heaps to provide the necessary heat. Aesculapian Snakes are the only semi-arboreal snake in Europe. Not only are they are excellent climbers but are equally at home high up in trees and bushes as they are on the ground. They can on occasion be found basking on the canopies of trees and tall bushes, or on roof-tops of buildings in their native range. They are regularly encountered on the edges of Beech and Oak forests at lower altitudes, as well as open grass fields and meadows surrounded by bushes, and dry stone walls. They can also be found in shrubs that border lakes and river banks.

Adult female Aesculapian Snake, Regent's Canal, London, 2016

So where did they come from and how did the three separate populations of Aesculapian Snakes end up here in the UK? 

1) Colwyn Bay population of Aesculapian Snakes in North Wales.

In 2006 the Welsh population of Aesculapian Snakes was estimated at around 85 adult and 365 juvenile specimens, and came about during the late 1960's after a gravid female snake, affectionately referred to as "Old Essie" by the 2003 assistant curator Peter Dickinson, escaped from the Welsh Mountain Zoo at Colwyn Bay and laid her eggs within the grounds of the zoo. The offspring then successfully bred and the population has thrived ever since in and around the zoo grounds. The first feral snake born within the grounds of the Welsh Mountain Zoo was found crossing a pathway within the grounds of the zoo in 1963, and was quickly identified as an Aesculapian Snake. It is possible that this colony derived from more than just one escaped specimen. According to the NNSS website the first official record of these snakes living wild in Colwyn Bay was in 1970. They were first reported by the press during the early '70's. Software analysis has however suggested that several individual specimens probably comprised the founder stock rather than just one specimen according to the 2009 book "The Naturalised Animals Of Britain & Ireland" by Christopher Lever". This population has not spread far from the zoo in 50 years confirming that this species probably has a low dispersal ability, and is reliant on woodland connectivity to travel. It is also likely that due to the abundance of rodent prey surrounding the Colwyn Bay Zoo that these snakes are reluctant to leave this food-rich location. The main egg laying site for this snake population has long been suspected to be the manure dump at the Zoo. Ongoing studies have revealed in 2021 that these snakes are using both the zoo's manure dump and offsite compost heaps as egg-laying sites.

The Welsh Mountain Zoo at Colwyn Bay was founded in 1963 by Robert Jackson. Robert Jackson was an importer and dealer of reptiles, amphibians, mammals and birds. One of the many species he sold in the 1950's & 60's was the Aesculapian Snake. See link here

2) Bridgend population of Aesculapian Snakes in South Wales.

On July 1st 2020 it was announced by Steven Allain and Dave Clemens that the British Herpetological Society had published their paper in issue 152, Summer 2020, of the Herpetological Bulletin, that announced a third population of Aesculapian Snakes living wild and breeding here in the UK. 

There is already the oldest UK Aesculapian Snake colony in North Wales but this new population is in Bridgend, South Wales. The two Welsh colonies of Aesculapian Snake are nearly 200 miles apart. This is almost the same distance as the London Aesculapian Snake colony is from the Bridgend colony.

The first report of an Aesculapian Snake to be found in Bridgend came from a member of the public after an adult snake was found in a residential garden on the 19th September 2016, although this wasn't made public knowledge until nearly four years later. Further investigation found that these Aesculapian Snakes were also present at nearby allotments. When questioned at the time local residents claimed that these snakes had been known to be around in their area for around 15 - 20 years. With a railway line nearby this feral population of Aesculapian Snakes differs from the other two populations found in the UK because it has the potential to disperse and spread considerably further from where it has currently been recorded. 

It is unknown at this time how large this population is or how far it has spread. It is also unknown how these snakes came to be in the area. The paper by S.Allain & D.Clemens mentioned the possibility that the founding snake could be an escaped pet or a deliberate release. My experience is that this species of snake is not overly popular in the UK pet trade and few reptile keepers choose to keep or breed this species here in the UK so I believe it is unlikely that this new colony is the result of an escaped pet. And if someone kept just one specimen as a pet then it wouldn't be able to start a new colony of snakes on its own if it did manage to escape. I have my suspicion that this could well be a case of deliberate release by someone wishing to start a new Aesculapian Snake colony in the area and I would be surprised if the founding specimen or specimens didn't originate from the Colwyn Bay Aesculapian Snakes. Surveys and studies of this newly discovered snake population will now commence by ARC-Trust to try and estimate the size and range of this new population. Hopefully DNA testing will be performed at some point to establish whether these snakes originated from a specimen of Aesculapian Snake from either the Colwyn Bay or Regents Canal population. This colony of Aesculapian Snakes is not believed to be as large as either of the two better established colonies in the UK. Since being reported in 2020 there have been no new sightings of Aesculapian Snake in the area, despite surveys being performed for them during 2021. However the CV19 lockdowns of 2020 and 2021 may be partly responsible for this. It is now unclear whether these snakes were all deliberately released there recently or whether they are actually breeding in the area.

BHS Herpetological Bulletin 152, Summer 2020, page 30 & 31

3) London population of Aesculapian Snakes.

I have personally been studying and photographing the Aesculapian Snakes in London now for over ten years, since 2011. My sightings and observations have continually been added to the database held by Will Atkins, as have records that I have forwarded to Will from other sightings by members of the public. By 2018 the London population of Aesculapian Snakes had seen 50 different adult specimens recorded and photographed, and in 2013 this population was then estimated at around 40 specimens. However the number of these urbanised snakes seems to have fallen significantly in London over recent years. Between 2016 -2021 the number of sightings has seen a definite decline and there are serious concerns as to how many of this once thriving population of feral snakes may still exist in 2022. This population is confined to a small area of around two hectares in Central London, surrounded by busy roads, and could only spread beyond this range by travelling along Regents Canal itself.

With the feral population of London Aesculapian Snakes being found in and near to the grounds of London Zoo it would be easy for one to jump to conclusions. But despite the obvious theory that the London population of Aesculapian Snakes must have derived from one or more escapees from London Zoo, this surprisingly probably isn't the case.

So if these snakes didn't originate as escapees from London Zoo then how did they get there? It is widely accepted that this population came about after about eight individual specimens of Aesculapian Snake were deliberately released along the banks of Regent's Canal in the mid 1980's from the "Centre For Life Studies", a building located at Zoological Gardens, Regents Park, NW1 adjacent to London Zoo and rented by ILEA (Inner London Education Authority facility for scientific experiments). Within the circles of respected herpetologists, some have claimed to know exactly which former ILEA staff member was responsible for releasing these snakes onto the banks of Regent's Canal. However some former ILEA employees insisted that these snakes escaped and were not deliberately released.

After repeated sightings of an unknown snake species on the banks of Regents Canal during the 1990s theses snakes were identified from photographs and in 1998 reported to TESL by Ester Wenman, who was at that time the head keeper of reptiles at London Zoo. This growing population of Aesculapians in London became common knowledge amongst many herpetologists in 2007, via a popular online British herpetology forum, and many travelled to London to find and photograph these snakes for themselves.

In an interview with the Camden Review in 2010 David Bird, a former zoo curator, also told the reporter that the Aesculapian Snakes either escaped from or were deliberately released from the ILEA building: Camden Review article

Christopher Lever discussed the London Aesculapians in his 2009 book "The Naturalised Animals Of Britain & Ireland" by Christopher Lever", and Will Atkins & Tom Langton then went into more detail about the origins of the London Aesculapian Snakes in 2011 when they wrote a detailed account in The London Naturalist No.90, 2011 on pages 93-95, giving this summary:

"A second feral population has been extant since the mid 1980s along a canal embankment habitat in Camden, north London. This was first reported to TESL in 1998 by Ester Wenman, then head keeper of reptiles at London Zoo. Aesculapian snakes had apparently colonised the area during an experiment reported by the British Herpetological Society Legal Officer, Peter Curry, who was working there and keeping this species at the Inner London Education Authority Centre for Life Studies at the time that it was closed down around 1986. One account was that eight snakes had been released ‘on the quiet’ around the time of closure to try to form a population, several of which were recaptured, but some remained at large. Those caught initially were being euthanized but the view was then taken to leave the others ‘to take their chances’ where they were. Ten years later, in an aviary close to the embankment, fragments of juvenile Aesculapian snakes were found in a laughing thrush Garrulax sp. aviary, suggesting that the snakes had bred."  The article also states, “Several newly born snakes were found in the basement of a building around 30 metres from the embankment in 2010, and breeding in that year was also shown in 2011 with a young 2010 cohort snake being located. To this date this is the only example of a non-native snake species breeding successfully and forming populations in the wild in London and the UK as a whole.”

A ZSL reptile keeper, who was working at London Zoo at the time when these snakes were released, claims these snakes were actually "deliberately released quite a while before the ILEA building was shut down". He claimed that during the 1990's the Aesculapian Snakes that were found by ZSL staff on the south bank of the canal would be captured and re-released back on the north bank of the canal, where the ILEA building was.

Natural England were slow to accept the existence of the London Aesculapian Snake colony. In their 22nd May 2009 report "Horizon scanning for new  invasive non-native animal  species in England", they discussed the Welsh colony of Aesculapian Snakes and went on to comment on the London colony saying " There are also anecdotal reports of individuals of this species in central London".  

The London Naturalist No.90, 2011, page 93 & 94

The London Naturalist No.99, 2020, page 96 & 97

In November 2020 the 99th edition of The London Naturalist published a lengthy summary by Will Atkins, based on his own sightings of the Aesculapian Snakes at London and those submitted to him. Will's knowledge on the London Aesculapian Snakes is second to none and his well written and in-depth article mentioned many points that I have also written about on this website. Will's views and opinions often echoed that of my own when discussing the conservation status and fears for the future of these snakes in the UK. 

Are there any other colonies of Aesculapian Snake anywhere else in the UK? 

On Sunday 13th June 2021 a post was added to Facebook by Jack Dabney clearing showing a photo of a wild Aesculapian Snake, seen climbing a wall in Ilfracombe, north Devon, on a sunny day that saw a temperature of 22 degrees. Jack claimed the snake was about 5ft in length. Other people were quick to reply to the post claiming also to have also seen similar snakes in the area. Whether these other claimed sightings were also of Aesculapian Snakes or of other native snake species is currently unknown. It's also unknown whether the definite sighting in Ilfracombe is an isolated specimen or whether there may be a fourth colony of these beautiful snakes waiting to be discovered in the UK. It certainly warrants further investigation. The former Ilfracombe Zoo existed in that area until 1973, so if more specimens are found in Ilfracombe then the question could be asked whether the zoo may have once accidentally been responsible for origins of a possible Aesculapian Snake colony in the area?  

This finding was shared to the UKARGS Facebook group by Ryan Holder, a local to the Devon area. LIINK. Alexandros Theodorou replied to the Facebook post that "There was also a record of an Aesculapian Snake near Weymouth while I was doing my Masters on them in 2016". Anthony Plettenberg also reinforced this comment by saying "On the other side of the peninsula, there was an adult found in 2016 in Weymouth. Similar situation - photographed, ID'd online, and probably still there". The 2016 Weymouth sighting was actually a juvenile specimen found early one morning by a member of the public in a carpark in Charlestown, Weymouth. However, with a local pet store & reptile specialist just a couple of hundred metres away from where this Aesculapian Snake was found it does make one question whether the snake may have escaped from there?

It is unlikely, but definitely possible, that there may already be further undiscovered populations of Aesculapian Snake in the UK waiting to be discovered. It is only by identifying random images of wild snakes found in the UK by members of the public, and then shared on social media, that these new populations could come to light. Unfortunately though many members of the public would simply disregard Aesculapian Snake sightings believing them to be different species of native snake.

Jason Steel photographing an adult female Aesculapian Snake along Regents Canal in London, UK in 2016. Photo taken by Australian photographer Diane Paine.

Are these snakes a threat to our native wildlife?

The simple answer to this question for the two populations of Aesculapian Snake at Regents Canal and Colwyn Bay is no. Following ongoing studies of these Aesculapian Snake populations in the UK by respected herpetologists including Wolfgang Wüster and Tom Major in Bangor, Wales, & Will Atkins in London, it is clear that the existence of these snakes has had very little if any negative impact on our native wildlife. This is largely because they feed almost entirely on common rodents which are in abundance around both zoos. Their primary prey in the UK is the Brown Rat, Rattus norvegicus. The Brown Rat is a non-native species in the UK that was introduced to the British Isles around 1720, as a stowaway aboard sailing ships.  LINK

In 2016 one adult Aesculapian Snake specimen that was handled by a fellow amateur herpetologist and friend of mine, quickly regurgitated six newly born rat pups. At this size the rat pups are far too young to leave their nest so this supports the knowledge that the Aesculapian Snakes are actively hunting rodents in their own burrows and hideaways. In 2021 another adult female Aesculapian Snake specimen, that was handled, regurgitated two young Brown Rats of 55mm & 60mm in body-length. Analysis of Aesculapian Snake droppings has also found traces of mouse hair. (The London Naturalist No.90, 2011, page 95). In 2021 studies of the Welsh colony of Aesculapian Snakes, by Tom Major & Bangor University, have revealed that these snakes have on occasion fed on ground nesting birds at that site too. Hatchling snakes there have fed on very young rodent pups. LINK  It's been reported in Croatia, where these snakes are native, that adult Aesculapian Snakes can feed as often as every three days in the warmer months. LINK

These snakes also seem dependent on woodland habitat connectivity in order to spread. In 50+ years since their arrival in the UK neither of these two populations of Aesculapian Snakes have been able to spread further than the sites where they are found. In London there simply aren't the necessary dispersal corridors available for the Aesculapian Snakes to disperse any further than they already have. And the population's distribution and reproduction is severely limited by the scarcity of suitable egg-laying sites.

It is largely down to the cooling climate over the past 5000 years that has seen a decrease in the distribution and numbers of Aesculapian Snakes across their native range in Continental Europe. With the undeniable current climate change that is already here and taking place across the world, temperatures are now on the increase. It is likely that the natural range of the Aesculapian Snakes found in Europe will change in the future. As temperatures continue to rise it is likely that many reptile species in Continental Europe, including the Aesculapian Snakes, will attempt to move further north and once again inhabit areas where they were previously found, if they are not prevented from doing so by busy roads that divide the land and isolate reptile populations in so many places. In Austria, where the Aesculapian Snake is considered both native and endangered, the Aesculapian Snake has already been recorded since 2014 as expanding its range both further north and higher in altitude. Where previously it was only found up to 1000m above sea-level it has now increased its range to 1200m above sea level. The same is also being seen with Adders in Austria. See link here.

With Aesculapian Snakes already present in the NW of France it is only the English Channel that prevents any possibility of theses snakes from returning to British soil of their own accord in future years. It is known from fossil records that Aesculapian Snakes have previously lived alongside our British native species in the past and given the opportunity could do so once again, probably without issue if they could reach our southern shores.

With the recently discovered population of Aesculapian Snake at Bridgend, South Wales, it is uncertain at this time what impact these snakes at Bridgend will have any the local environment because unlike the other two Aesculapian Snake populations already found in the UK, these have the potential to disperse and spread. However Aesculapian Snakes are found across much of Europe living side-by-side with many of the same species of wildlife that we have in the UK without any issues so it is still very unlikely that they will become a threat to other native species.

Adult female Aesculapian Snake, Regent's Canal, London, 2016

Are these snakes dangerous to humans?

No, not at all. The Aesculapian Snake is non-venomous and not an aggressive species. It also lacks the size or strength to inflict any harm to either humans or pet cats & dogs. Unless you're a rodent, a small bird or a young lizard, then you're quite safe from these snakes, despite what the press would have you believe.

Adult female Aesculapian Snake by Regent's Canal, London. 2016

The London population of Aesculapian Snakes can be found along the length of Regent's Canal as it runs past Regent's Park, living on both sides of the steeply sloped banks that run parallel to the canal. In my years of photographing the London Aesculapian Snakes I have encountered roughly the same number of snakes on both the north side of the canal and the south side. With our native herptiles it would be expected that only the north bank of the canal, which is south-facing, would be suitable for their basking requirements. But being a semi-arboreal species it is possible that Aesculapian Snakes are not as reliant on a south-facing slope as our native ground-dwelling reptiles as long as there are small trees and bushes with canopies that present suitable basking opportunities.

Adult female Aesculapian Snake, Regent's Canal, London

It is believed that Aesculapian Snake specimens found in London tend to be slightly larger than those in Colwyn Bay and this could be one possible effect of in-breeding by the Welsh snakes, if there is truth in the rumour that the Welsh population of Aesculapian Snake all derived from a single escaped specimen. A 1960 photo of an Aesculapian Snake supplied by Robert Jackson, a well known reptile dealer and the founder of the Welsh Mountain Zoo, depicts an Aesculapian Snake of good size suggesting that maybe the original escapee that formed the wild population of Aesculapian Snakes in Wales might have been larger than those Aesculapian Snake specimens now found there today

The Welsh population of Aesculapian Snakes is now the most northerly extent of this species' range across the world, and this could explain why the Welsh Aesculapian Snakes are not only shorter but also marginally lighter in colour than Aesculapian Snakes found in warmer and more southern parts of Europe where they occur naturally.
These snakes are native to central and eastern Europe and it is believed that the Welsh population derived from snakes originating from Central Europe, possibly Italy. However as yet no DNA testing has been done, or results released, to confirm the origin of the London population of Aesculapians.

Adult female Aesculapian Snake, Regent's Canal, London, 2016

Unlike all the other snake species found in Britain, it is the male Aesculapian Snake that is usually longer than the female. The female has greater girth but the male tends to be much longer. The female pictured above had a total body-length of just 3.5ft. A male specimen with equivalent girth would probably have been 5ft+ in length.


Adult female Aesculapian Snake, Regent's Canal, London, 2016

So what makes the Aesculapian Snake so special?
With the exception of the atypical Grass Snakes found in the UK, the Aesculapian Snake is the only non-native snake species to ever form a successful breeding colony in Britain. Not only have they managed to achieve this in separate locations, but they have also managed to do this without upsetting the delicate balance of the ecosystem in which they are found and the surrounding wildlife. However, two of the colonies of Aesculapian Snake found in the UK are within the immediate proximity of local zoos and are probably dependent on the food source of rats and mice attracted to these zoos. Should either zoo close down then it is questionable whether the rat numbers in the area would still be sufficient to sustain either snake population at the levels they are at now. The Aesculapian Snakes found at Regent's Canal are even more special in my opinion for several reasons: Firstly, they are an egg-laying species which means they are far more dependent on suitable conditions to successfully hatch their young. They have also managed to survive for 30-35 years, against all odds, in the centre of one of the busiest capital cities in the World. They have been given no help to aid their conservation over the years and to continue surviving they just need to be left in peace. And whilst living on the Banks of Regent's Canal and within the grounds of London Zoo they provide a valuable vermin control service free of charge as they feed on the rats and mice that plague most zoos. Peter Dickinson, a former assistant curator at the Welsh Mountain Zoo, once wrote that the Welsh Mountain Zoo was unique amongst zoos in the fact that it was the only zoo he knew of that wasn't plagued by rats. He contributed this rodent control to the presence of Aesculapian Snakes living within the grounds.

Notice the short and rapidly tapering tail indicative of a female Aesculapian Snake, Regent's Canal, London, 2016

What months of the year are the Aesculapian Snakes active?
Due to the micro-climate of Central London, and its slightly warmer temperatures, if the survey data from the UK Aesculapian Snake sites were to be analysed I would expect it to reveal that the London Aesculapian Snakes are able to emerge from hibernation slightly earlier and enter hibernation slightly later than the Aesculapian Snakes found at both the Welsh Aesculapian Snake sites. In London the Aesculapian Snakes have been recorded regularly from April right up until the very end of September, as long as the temperatures remain close to 20 degrees. In 2021 a very mild November resulted in one sighting of an adult Aesculapian Snake being observed crossing the tow path by Regents Canal on the 11th of November. This was the first time this species had been observed to still be active so late in the year in London. Whilst it is possible that the snake may have been disturbed from its sleep it is more likely that the snake had remained active until that point due to the mild temperatures during the autumn of 2021, and was on its way back to its hibernaculum when it was seen. It definitely wouldn't have been hunting rodents at that time of year though as snakes need to hibernate on an empty stomach. Recording the exact location of this sighting, and the direction the snake was seen travelling in, may help us to work out where these snakes hibernate during the colder winter months at Regents Canal.

Adult female Aesculapian Snake, Regent's Canal, London, 2016

These elegant snakes range in colour from light golden-brown to dark brown with white flecks and a creamy yellow underside. Aesculapian Snakes have unkeeled scales that are very smooth to the touch and this snake can have a very shiny appearance with an iridescent sheen in bright sunlight. Their overall appearance of the London Aesculapian Snakes is often compared to that of a Twix wrapper.

Adult female Aesculapian Snake, Regent's Canal, London

This adult female specimen at London exhibits several scars along her body. These may have been caused by attempted predation by birds, foxes, domestic cats, or by defensive rodents and some snakes have suffered as a result of encounters with local council workers or groundsmen using strimmers to cut the grass. Groundsmen workers at ZSL bear witness to Magpies being seen attacking these snakes on several occasions.


Adult female Aesculapian Snake, Regent's Canal, London

Will Atkins has been photographing and recording individual specimens of the Aesculapian Snake population in London since 2007. His photographic database allows him to identify individual snake specimens by studying unique scale markings on the head of each snake. This close-up shot of the snake's head shows the smooth un-keeled scales of the adult female Aesculapian Snake, number 15 of the London population, identified from Will Atkin's database.

This individual snake has been recorded on both sides of the canal. Whether it uses the footbridges or whether it swims across the canal is uncertain as these snakes have been filmed by members of the public on and adjacent to the footbridges. In 2011 I spoke to the owner of a canal-boat moored along Regent's Canal in 2011 who told me had had once seen a 6ft snake swimming in the middle of the Regent's Canal. Despite this species often being found in the vicinity of fresh water in Europe the Aesculapian Snake, unlike the Grass Snake, is not a species that is known to readily take to water unnecessarily, but does on rare occasion. LINK.  In other European countries, such as France, where the Aesculapian Snake is considered native, the typical range for a male specimen is around 1.14ha, however males have been known to travel distances of 2km in search of females during the mating season. Likewise females can travel similar distances in search of suitable egg-laying sites too. Ongoing results in June & August 2021, from the ongoing radio-tagging of Aesculapian Snakes in Wales by Tom Major, has shown that these snakes move about a great deal. Those specimens being monitored in Wales are proving to spend a lot of time in, under and around buildings, where they're hunting for rodents.

For reference see page 3 here:  LINK 

Adult male Aesculapian Snake at Regents Canal, London, 24th May 2012.

Juvenile Aesculapians are usually pale yellow with several rows of dark brown spots. They usually display a yellow collar making them easy to confuse with juvenile Grass Snakes. However Juvenile Aesculapians can lack the dark collar that is nearly always adjacent to the yellow collar found on Grass Snakes. This yellow collar fades and then disappears as the Aesculapian Snake reaches maturity, unlike Grass Snakes which usually retain this yellow collar throughout most of their life, especially males. Juvenile Aesculapian Snakes also usually have a black mark behind the eye that runs to the neck. Like Grass Snakes the Aesculapian Snake is an egg-laying snake and adult females usually produce clutches of 5-20 eggs with 5-11 being common. These eggs are grooved and can be as large as a hen's eggs. 

The eggs hatch after 6-10 weeks, depending on the weather and incubation temperatures. Aesculapian Snake hatchlings are slightly larger than that of a Grass Snake, usually measuring around 15-20cm in length. The hatchlings can vary in size though and have been recorded ranging from 12-37cm in length in Europe. 

In London gravid females have been seen in mid-July and the same specimens have been seen again during the first week of August already having given birth. This puts egg-laying for Aesculapian Snakes in London at the end of July which is the same as in Continental Europe where the Aesculapian Snakes are considered native.

Adult male Aesculapian Snake, Regent's Canal, London, 2019

In captivity Aesculapian Snakes can live for 25 - 30 years, however due to predation it is unlikely that most wild specimens would live anywhere near that long. Aesculapian Snakes reach sexual maturity after approximately 4-6 years. Male Aesculapian Snakes reach sexual maturity when they reach around 100cm in length, and females at just 85cm in length. Like many species of snakes adult male Aesculapian Snakes engage in wrestling contests to win the right to mate with a female during the breeding season. Webster Forrest captured a short clip of this behaviour on his phone back in 2017 on April 30th along the banks of Regents Canal, London. The video is copyright of Webster Forrest  but can be viewed here:  Aesculapian Snakes Combat

Adult male Aesculapian Snake, at Regents Canal, London, May 2012.

Slithering along the branches of this tree, the Aesculapian Snake is a very competent climber. They use their strong prehensile tail to grasp a firm grip when climbing or when being handled.


Adult male Aesculapian Snake with a total length of 4 ft 5 inches, including tail. Regents Canal, London 2012.

The London Aesculapian Snake is not as timid as our native Grass Snake and can often be approached for photographs without disturbing it or causing it to flee. They rely heavily on their excellent camouflage and will often remain completely motionless until they are sure that you have seen them. Although usually a shy and secretive species due to the high levels of human traffic that pass by the London Aesculapian Snakes everyday some specimens have become pretty fearless of human contact. 

There have been several occasions when these snakes have been spotted and filmed crossing both busy pathways and the canal bridges in the middle of the day when there are plenty of people about. There have been three videos posted on-line during 2019 and 2020 of an adult female Aesculapian Snake using a bridge over Regents Canal. It is possible that these are all videos of the same individual snake that has deemed it safer or easier to cross the canal via the bridge, even with people about, than risk crossing the busy canal by water.   

  VIDEO 1  -  VIDEO 2  -  VIDEO 3

Adult male Aesculapian Snake with a total length of 3.5 ft at Regents Canal, London. 2019.

If handled Aesculapian Snakes will often immediately thrash about in an attempt to escape, and may initially bite, but they usually calm down quite quickly, and once they no longer perceive you as a threat they can be very relaxed in your hands. Being constrictors, these snakes have a very strong grip. When startled it's surprising how firmly they can squeeze your hand. Technically by handling a non-native species you are committing an offence when you release it again into the wild without a licence, so I don't encourage anyone to handle a wild Aesculapian Snake in the UK. 

Adult male Aesculapian Snake (Snake 27 on Will Atkins records),  at Regents Canal, London. 11th July 2011.

One of two specimens photographed high above the ground basking in the canopy of a large bush at London in 2011. Aesculapian Snakes prefer slightly warmer temperatures to our native snakes and Aesculapians have been observed most often when temperatures have been between 16 - 25 degrees C, with 21-24 degrees being the favoured range.


Adult female Aesculapian Snake (Snake 7 on Will Atkins records), at Regents Canal, London. 11th July 2011. 

The second of two specimens photographed high above the ground basking in the canopy of a large bush at Regent's Canal, London in 2011.

Adult female Aesculapian Snake (Snake 7 on Will Atkins records), at Regents Canal, London. 11th July 2011. 

Feeding mainly on mice, voles, young rats and other small rodents these non-venomous constrictor snakes have also been known to eat lizards, small birds and eggs if necessary. Like most snakes the Aesculapian Snake sheds its skin periodically in one complete slough. Apart from a noticeable dulling in colour and pattern, one obvious indication that a snake is due to slough is the clouding over and bluing of the scale covering the eyes of the snake as pictured above. This eye-scale will shed first and then the rest of the snake's skin will usually shed a few days later as a complete slough.


Adult male Aesculapian Snake found slithering through low vegetation at the edge of the towpath along Regents Canal, London. 2019

Male Aesculapian Snakes, like many other species of snake, engage in combat with rival males for the right to mate with female Aesculapians. These battles usually consist of wrestling matches where the two male snakes intertwine their bodies and try to force their opponent to the ground until one male gives in and retreats. If the snakes are similar size and equally matched in strength then these fights can last for over 90 minutes and frustrated snakes can resort to biting each other to win. This behaviour has been excellently captured on film in the Czech Republic where these snakes are classed as critically endangered.  Watch video here.

Adult male Aesculapian Snake at Regents Canal, London. 2019

Aesculapian Snakes have angled ventral scales on either side of their body which grip extremely well to rough tree bark and enable them to climb vertical tree trunks in search of basking opportunities in woodland or to hunt for birds and their nests in the branches. Despite the excellent climbing abilities of the Aesculapian Snake most specimens that have been recorded in London were found on the ground, where they feed exclusively on the abundance of local rodents. This is also true of the Welsh populations of Aesculapian Snake, as well as in the Aesculapian Snake's natural habitat in many European countries, as mentioned in "The Snakes of Europe" by Guido Kreiner.  In Hungary, where the Aesculapian Snake is native, they are referred to locally as as 'Forest Gliders' and they are known to regularly hunt in trees for nesting birds and eggs. One Hungarian study of nesting birds, using man-made nesting boxes, had to be abandoned after it was discovered that many of the birds using these nesting boxes were being hunted by Aesculapian Snakes.

Adult male Aesculapian Snake at Regents Canal, London. 2019

Adult male Aesculapian Snake at Regents Canal, London. 2019

Members of the public walk past blissfully unaware of the 4ft+ slithering, urban serpents that share this habitat. Due to the constant exposure to high levels of human traffic passing by Regents Canal the London Aesculapian Snakes have learned to have little fear of humans and are far easier to photograph. Photographing this species in public provides an excellent opportunity to talk to curious passersby and educate them about these beautiful creatures and their role in the ecosystem. The reaction from members of the public is usually one of complete surprise that these exotic creatures live in London, followed by fascination.

116cm male Aesculapian Snake at Regents Canal, London. September 2020

This 116cm adult male Aesculapian Snake was previously unrecorded and was found basking on the north bank of Regents Canal at 10:39am in September. The air temperature was 17 degrees and there was about 50% cloud cover.

Aesculapian Snakes don't usually rely on ambush tactics and are rather more of an active hunter. Prey is often hunted and subdued in its own hiding place. Adult rodents are usually killed by constriction before being swallowed head first. Many Aesculapian Snakes exhibit scars possibly obtained from previous encounters with the sharp teeth of defensive rats. The specimen above shows damage to its scale around its right nostril.

110cm female Aesculapian Snake at Regents Canal, London. 16:30 July 21st 2021

This highly defensive, adult female Aesculapian Snake was basking openly in short grass late in the afternoon at the top of the north bank of Regents Canal. The temperature was a very high 28 degrees. Aesculapian Snakes are rarely seen when the temperature is above 25 degrees, but basking in this heat would have helped the snake to digest the two young Brown Rats it had just eaten. 

These two young Brown Rats, of 55mm & 60mm in body-length, were regurgitated by an Aesculapian Snake when it was handled.

Adult female Aesculapian Snake at Regents Canal, London. 2019

This 4ft adult female Aesculapian Snake was found coiled on top of a log-pile in dense woodland habitat along Regents Canal. Its entire body was in the shade with just its head exposed to occasional flickering sunlight.

An adult Aesculapian Snake basking at the edge of the canal towpath amidst ground ivy, 6th September 2021, 

This large Aesculapian Snake was basking in the morning sunshine at 10am, on a hot September morning, when the temperature was already 23 degrees. The snake basked for around 30 minutes before slithering off into the undergrowth. By midday the temperature had reached 27 degrees. Whilst basking the snake regularly adjusted its position so different parts of its body were exposed to the warmth of the sun. Unlike a Grass Snake or an Adder, which would both flee when approached, this Aesculapian Snake relied entirely on it camouflage against the dead twigs and leaves beneath it. I was able to approach it with my camera several times and get within 30cm of the snake without causing it to move at all. It remained completely motionless whilst it sensed I was watching it. Unfortunately this form of defence does has its disadvantages as Aesculapian Snakes won't always get out of the way when council workers are cutting the grass with strimmers and at least one Aesculapian Snake specimen has been seen at Regents Canal with very bad scaring caused by a strimmer in past years. 

Aesculapian Snake bites incurred as a result of handling the snakes.

Do Aesculapian Snakes bite?

Aesculapian Snakes vary in temperament, but they are usually a fairly calm species. Many specimens do not bite even when handled. Some specimens do hiss and strike when handled but this is often with a closed mouth to serve as a warning. Others may make a strike and bite without attempting to inflict any real harm, just to get you to release them. It is reported that sometimes Aesculapian Snakes will inflate themselves in a threat display but this is not something I have witnessed myself. Other specimens can be very defensive though and will quickly bite if handled. I have found female specimens to be more likely to bite if handled, particularly in hot weather.

I must stress that there is no chance of being bitten by one of these snakes unless you try and pick one up! They will always flee rather than confront a human.

The bite marks shown in the both images above were inflicted by defensive adult female Aesculapian Snakes.  This account is by "someone" who picked up a wild Aesculapian Snake along Regents Canal in 2016:  

"I spotted a large adult female Aesculapian Snake on the canal's edge, mosaic-basking amidst grass and dead twigs on the ground. Only a few inches of the scales on the middle of the snake's upper body were visible, as the rest of the snake was buried beneath the protection of the surrounding foliage. When I carefully picked up the snake to photograph the head for identification purposes, to my complete surprise, an angry, wide-mouthed head quickly spun round and latched onto my wrist. Having never experienced any signs of real aggression from Aesculapian Snakes during previous encounters, I was very surprised by how intent this snake was in defending itself from what it perceived to be a potential predator. It wasn't just biting me, It was rotating and twisting its entire body around in my hands whilst continuing to clamp its jaw around my wrist. It really meant business! After about 10 seconds it released the grip that its jaws had on my wrist, and it immediately turned its attention to my hand and began biting again. Then released, and then bit again! Then released, and then bit again!

It took me a while to realise that this snake, although drawing blood with every bite, was incapable of inflicting any real harm or pain on me. It had extremely sharp little teeth but lacked the sufficient clamping power in its jaws or the necessary tooth size to do me any real damage. After a few minutes, the snake also came to the same conclusion, and once it also realised that I wasn't actually a threat or causing it any harm it began to calm down. After a while it became quite docile and was content to slither around or just relax in my hands and enjoy the warmth for a while before being released back to the exact spot where it was found."

Although considered completely harmless many colubrid snakes have very slight traces of very mild venom in their saliva produced by the Duvernoy's gland. Studies on Garter Snakes have shown that this mild venom could aid subduing mammalian prey when the snake grasps and holds the prey in its jaws for several minutes. Even though Aesculapian Snakes have tiny teeth, and are incapable of causing any real harm or pain to humans, the small puncture wounds can cause quite a reasonable amount of blood to flow from the wound making it appear to be far worse than the superficial scratch that it actually is. Jonathan Cranfield, of Herpetologic, has commented that this "suggests that there are anticoagulant enzymes at work" from the Aesculapian Snake's saliva.

Read the paper by W & F Hayes here.

 147cm slough (old snake skin that has been shed) from an Aesculapian Snake, found on the north bank of Regents Canal, September 6th 2020.

Careful comparison of the scale formations on the head of this slough can be compared with close-up photos of snakes previously encountered at Regents Canal to identify exactly which specimen of the London Aesculapian Snake population this slough came from. The shape and size of these head scales is unique to each individual specimen and identifying and recording individual snakes can enable us to build up a history of their movements on this site and help gain a better understanding of their behaviour. The slough pictured above was sent in 2021 to be studied for genetic analysis of the Aesculapian Snakes in the UK by Tom Major and the Bangor University.

Aesculapian Snakes In The News

These Aesculapian Snakes living in London have made the news headlines many times over recent years but May 2014 saw a series of disgraceful reports by the British media about the Aesculapian Snake colonies found in the UK. These sensationalised and scaremongering stories were full of false information and inaccurate reports with ridiculous claims and headlines including the Daily Star's "KILLER snakes that are capable of crushing small children to death are on the loose in Britain! " the Daily Mail's "London hit by outbreak of invasive eight foot snakes that could kill cats or small dogs!" and the Metro's "Army of 6ft 6in snakes capable of killing young children on the loose in London"

Daily Star      Daily Mail       The Mirror (amended)       UK News Yahoo      International Business Times      Travel AOL      Metro      Hackney Gazette

Less dramatic reports from these news websites:

Camden New Journal      London Live      The Islington Tribune      Express      Independant      Daily Post      Vice (excellent article)

Aesculapian Snake found in toilet

Aesculapian Snakes are well known to enter buildings whilst hunting for mice and rats to feed on. On 10th August 2021 the Austrian Zenger News ran a factually accurate story about an Aesculapian Snake that had entered a home in the town of Breitenfurt, located near Vienna, the capital of Austria, on 7th August 2021.

The home owner had taken his toilet apart to investigate why it kept mysteriously flushing itself. When the cistern was opened the man was shocked to find a six and a half foot snake coiled up inside. Emergency services were called and the snake was captured and identified as a harmless Aesculapian Snake. The snake was released into a nearby forest.     LINK

Whilst it has always been believed that Aesculapian Snakes enter houses in pursuit of rodent prey, maybe they just popped in to use the toilet?

The story was also picked up by other reporters, including News 18, who chose the run the usual sensationalised press garbage, full of lies and inaccuracies, claiming that the Aesculapian Snake grows to five metres in length and was released back into the jungle. Even the photo that accompanied their news story was a Burmese Python, the wrong species of snake.    LINK

The story was even picked up by the British press including the Sun, who ran a factually accurate story, and the Mirror, who chose to withhold the species of snake so they could also print photos of of a species of snake not connected with the story.    The Sun,    Mirror

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Being classed as a non-native species are the Aesculapian Snakes likely to be removed?

Despite these snakes posing little if any threat to our native wildlife (excluding mice and young rats) in 2013 the Government agency 'LISI' (London Invasive Species Initiative) decided that these Aesculapian Snakes were a species of concern and called for the snakes to be eradicated in the UK, quoting them as a "Species of high impact or concern". You can download the list of "Species of concern in London". Thankfully LISI seemed to listen to experts on these snakes and in 2014 LISI responded to the sensationalized media stories and released the following statement alleviating any unnecessary fears and stating that they had no immediate plans to remove these snakes from the wild at least until further studies of their impact on native wildlife have been carried out. However as of yet Natural England have refused to grant any licences to study the Asesculapian Snakes in London.

 Killer snake headlines debunked

"There have been some interesting headlines over the weekend regarding Aesculapian snakes in London, such as the Daily Mirror’s ‘Colony of killer snakes ‘capable of crushing small children to death’ on loose in London’.

The London Invasive Species Initiative (LISI) has put together some information which we hope will clear up some inaccuracies. Below is our original statement, in response to a request for information on their population in London. Note that LISI is not calling for the eradication of the species in London, as reported in some media.

'The species of concern list for the Greater London area has been compiled by a range of industry professionals and land managers within London and is reviewed and updated quarterly. This list does indeed include the Aesculapian snakes that are being referred to, although no action that I am aware of has been taken to remove this population, nor does LISI have any plans to do so at present. This species is listed in the Wildlife and Countryside Act 1981 meaning it is illegal to allow the species to spread or escape into the wild. At present there is limited information on what effects the species may have on our local ecosystems and further information would be hugely valuable in developing appropriate management plans for this population’.

LISI would require further information and monitoring of this species before advising on any further action. With so many other invasive non-native species having a detrimental effect on our environment, it is not feasible to spend limited resources on a species that does not at present seem to be having a significant impact on our ecosystems.

As for the concern about people’s safety, when left alone Aesculapian snakes are a docile and non-venomous species. Please rest assured that your children will not risk being crushed by snakes whilst wandering through central London."

The decision on what action should be taken regarding any non-native species is usually made by the Non-Native Species Secretariat (NNSS). The NNSS undertakes risk assessments for any non-native species and would consider many criteria such as:  Is the species likely to spread? Does it feed mainly on other non-native species or rarer native species? Is it a threat to people? Is it a carrier of dangerous pathogens that could affect native species? If such criteria are used to make a decision on the Aesculapian Snakes in the UK, and if common sense prevails, then hopefully those in power will agree that these snakes pose no threat to people and very little, if any, threat to our native wildlife and could be safely left to their own devices. 

Speaking to Brian Banks, previously involved with the Natural England project to remove American Bullfrogs from the UK in the late 90's, he made it known that the project cost a six figure sum back then to remove the American Bullfrogs from sites across the UK. The American Bullfrogs were a highly invasive species and a very serious threat to our native wildlife. It's hard to imagine that a now poorly funded Natural England would find the necessary funds to consider the Aesculapian Snakes a threat serious enough to warrant such a huge expenditure. 

Aesculapian Snakes are still under threat from government action though and on 15th October 2019 the House of Commons Environmental Audit Committee released their First Report of Session 2019 on Invasive Species. On page 38 of the report the Aesculapian Snake was listed as a "species which are already established in GB and which are potential priorities for rapid eradication".

Adult male Aesculapian Snake, Regents Canal, London. 2012

So what does the future hold for the London Aesculapian Snakes?

With many people incorrectly pointing the finger at ZSL being responsible for the escape of the original Aesculapian Snakes that founded the London snake population, in 2016 rather than attempting to remove the snakes from Regents Canal, based purely on my own observations, the action that appeared to have been taken was to lay high numbers of rodenticide bait traps in the areas that these snakes were known to use as feeding grounds. By reducing the available prey for the snakes it would have made it far harder for them to survive.  It's also highly likely that some snakes have been killed as a result of secondary poisoning after feeding on poisoned rodents at Regent's Canal. In May 2020 I was emailed after a member of the public found a dead adult Aesculapian Snake at Regents Canal. The dead snake showed no signs of injury and is quite likely to have died as a result of secondary poisoning. This reinforces my views that at least part of the blame for the dramatic reduction of Aesculapian Snakes at Regents Canal is likely to be due to these rodenticide bait traps used by ZSL. Bangor University have obtained a licence permitting the capture and re-release of the non-native Aesculapian Snakes found around the Welsh Mountain Zoo, as part of their ongoing studies of this species. Sadly ZSL have never applied for such a licence and  Aesculapian Snakes, found within ZSL grounds by ZSL staff over the years, have been captured and either euthanised or taken into captivity. ZSL have within their collection some dead and preserved Aesculapian Snake specimens that were once caught within their grounds.

A quote from a member on reptile pet forum in 2018

Some Aesculapian Snakes from Regents Canal have also suffered at the hands of selfish collectors and I have personally witnessed some members on reptile forums boasting of their intent to catch and keep wild specimens from the London Aesculapian Snake population. ZSL have also caught members of the public catching feral Aesculapian Snakes within the grounds of the zoo.

Numbers may also have fallen due to a lack of breeding success with a short supply of suitable rotting vegetation or manure piles needed for egg incubation. It is also very possible that some specimens may have been deliberately killed by ignorant people who fear snakes. 

In 2019 the number of rodent traps being I observed in the area seemed to have been reduced slightly from 2016. And with no immediate action being planned to remove these snakes at present it is hoped that they will be left free from persecution and be allowed to live in peace. With so many other more harmful and invasive species such as the Grey Squirrel now being accepted as part of the British wildlife it is hoped by many that these small and restricted populations of harmless snake will also be one day accepted too.

Although breeding of the London Aesculapian Snakes has obviously successfully occurred many times since the 1980's there seems to have been very limited success in recent years. To the best of my knowledge there have only been 2 juvenile specimens recorded in the last 10 years in London. The first by Will Atkins, and the second recorded on May 16th 2017 by Chris-26 on

August 2019 - As part of a debate on the future of Aesculapian Snakes in the UK, held on Facebook , world renown herpetologist Dr Wolfgang Wüster made the following comments in support of these snakes:

"I always get a chuckle out of these discussions of introduced species and the supposed threat they pose to natives. The underlying assumption (as in so much of the UK herp conservation scene) seems to be that the status quo, with our native species in the habitats they've always occupied, is still on the menu. Sorry folks, but that is just wishful thinking. Climate change is in progress, and we are seeing more of its effects every year. And while countries sign pious pledges in Kyoto, Paris and elsewhere, a look at the global scene right now (Trump, Bolsonaro etc.) suggests that it would take an unusual degree of optimism to believe that humanity has the collective will and the structures in place to significantly reduce emissions to the levels required to prevent the worst of climate change. We are in for a rough ride.

With climate change as forecast in any of the current humans-doing-too-little-too-late scenarios, not a single global ecosystem will be unaffected. "Nature", in the sense of environments unimpacted by humans, is effectively dead. There's a word for that: the Anthropocene. We are in it, and we are running the show. And since that is where we are, I suggest we would be better off owning it and trying to make the least worst of it, than pretending it's not happening,

For biodiversity, that means that the status quo is not an option. Organisms that can swim or fly will adjust their distributions accordingly under their own steam. It's already happening. Small terrestrial organisms generally don't have that choice in our fragmented landscape. So our options are to do nothing while we pretend that we don't want to interfere with a non-existent nature, while we watch the less adaptable species disappear and Britain's biodiversity decline, without any new diversity coming in to replace what is lost, OR we can decide to manage the situation and maintain overall biodiversity, and that could include welcoming non-native central European species that will now come under pressure in the southern parts of their distributions. The Aesculapian snake (as well as wall and green lizards and other Central European species) are perfect examples of that. They already interact with the same species as our natives in their current native range (so that chances of a disastrous impact are minimal even if they were to spread), and they are likely to end up having a hard time in parts of their native ranges. Why not welcome them here?
Note that I am ABSOLUTELY NOT advocating a free-for-all! We don't want introduced bullfrogs, corn snakes, Russian ratsnakes, red-eared sliders or other species from the other side of the world to proliferate here. But species from neighbouring regions that would get here anyway but for the Channel? I really think we need to rethink our attitudes there, and take into account the bigger picture of where we are headed."
  -  Dr Wolfgang Wüster

In 2020 the habitat around the banks of Regents Canal has changed considerably over the last 35 years since the introduction of the Aesculapian Snakes to London. The grassy banks that once afforded the snakes plenty of basking opportunities have now been largely replaced by Sycamore, Hazel and Hawthorn due to the lack of maintenance at the site. This lack of suitable habitat is possibly contributing to the reduction of snakes now found at Regents Canal. The snakes will be forced to either rely more basking in tree and bush canopies or bask at the edge of the woodland, where they are at far greater risk of coming into contact with members of the public. Sympathetic management to the area would not only benefit the Aesculapian Snakes but would benefit many other species of wildlife too. 

With the odds stacked steeply against the future survival of the Aesculapian Snakes in London it is feared that these wonderful, harmless creatures are unlikely to have much of a future ahead of them. It saddens me greatly to believe that we will probably allow this fascinating species, that is already in decline across the world where it is considered native, to be lost from our country for good. It is highly likely that the Aesculapian Snakes will not survive for much longer than another decade in London unless there is a serious change in attitude towards the presence of these snakes by government bodies responsible for wildlife conservation in the UK.

Most recent sightings at Regents Canal 2020, 2021 & 2022

Confirmed Aesculapian Snake sightings have been recorded in London as recently as 16th May 2022, when Chris-26 spotted an adult Aesculapian Snake on the south-bank of Regents Canal. Also on the 16th May 2022, Andy Youngs spotted an adult Aesculapian Snake on the other side of the canal on the north bank.

On 8th May 2022, when Vo Goa spotted a dead 3-4ft Aesculapian Snake at the edge of the towpath by Regents Canal. The last record of 2021 was on 11th November, when Professor Aladin Aladin found a 3-4ft Aesculapian Snake crossing the towpath by Regents Canal. This is the only record in the UK of this species being seen as late in the year as November that I am aware of.

On 13th September 2021 Clive Moss & Joel Dixon found a two foot specimen on the north bank of the canal. On 6th September 2021 I photographed a adult specimen, probably female, basking amidst ground ivy at the edge of the canal towpath. On the 3rd September 2021 Laura Rivkin saw an adult specimen basking on top of a bush on the north side of the canal. On the 14th August 2021, Chris Roughley photographed an adult Aesculapian Snake basking just within the grounds of ZSL, on the north bank of the canal. On the 9th August 2021 an adult Aesculapian Snake was seen shedding its skin on the north bank of the canal by Peter Bordass. On 21st July 2021 I photographed an adult female basking at the top of the north bank of the canal. On the 26th June 2021 a 1.5 - 2 metre Aesculapian Snake was seen, and reported to me, on the north side of the canal, by Laura Rivkin.  On 31st May 2021, by David Jones, who found two adult specimens on the south-facing bank. One adult specimen was found the day before on the north-facing bank on 30th May 2021 by Lawrence Hills. On 6th September 2020 I found a 116cm male specimen on the North Bank of Regents Canal as well as a 147cm Aesculapian Snake slough (old snake skin that has been shed) from a different male Aesculapian Snake specimen along the banks of Regents Canal on the same day.

Recent unconfirmed records, not supported by photos:
Theo Uys witnessed an adult Aesculapian Snake, of around 6ft in length, cross the canal tow path on the north bank and disappear into the grounds of the zoo on Sunday 18th July 2021.

Charlotte Page saw a dead 2ft snake, on 15th July 2021, floating in Regents Canal, which she believes was an Aesculapian Snake. The dead snake was found floating in the water under Wharf Road Bridge in Angel, Islington. No live Aesculapian Snake specimen has ever been recorded this far down the canal and this corpse is likely to have been carried some distance by the current of the canal. Unfortunately without a photo to confirm the identity, and at just 2ft in length, we must also consider that this may have been an escaped pet snake rather than an Aesculapian Snake that had travelled from further up the canal.

A snake sighting near Regents Park was brought to my attention on 4th August 2021. This non-native snake was seen crossing the main road during the middle of the day. On this occasion though the snake was not an Aesculapian Snake but a Corn Snake, which was obviously either an escaped, or deliberately released pet snake.  LINK

Is it possible some of the London Aesculapian Snakes did originate from London Zoo?

There is an interesting piece written on pages 181-182, in the book "Wild Animals in Captivity" by the late A.D.Bartlett, the superintendent of Regents Park Zoo during the late 1800's. He tells of his experiences where wild-caught brown mice were introduced to snake enclosures as a source of live food. If the mice weren't caught and eaten by the snakes fairly quickly, then the mice would gnaw their way out of the enclosures, leaving a rodent-sized hole for the snake to also escape from. The practice of feeding these wild-caught live brown mice was stopped once the mistake was recognised, but not before a highly venomous cobra had escaped. Luckily this cobra was eaten by another snake in the adjoining enclosure. But A.D.Bartlett also recalls:

"Years after the old reptile house had been disused, harmless snakes that had escaped in this way were found in the mill-room underneath the old house. They had doubtless lived upon the rats and mice that swarmed in this place."

The full book is available to view on-line here:   Wild Animals in Captivity - by A.D.Bartlett

With this information available it's easy to see how someone might question whether there is an unlikely possibility that maybe some of the specimens of Aesculapian Snake still found along Regents Canal could indeed have originated from escapees from ZSL? 

Despite some claims that ZSL never kept Aesculapian Snakes at their zoo, page 6 of the 32nd Edition, Zoological Society of London guide book dating back to 1935 (as seen below) confirms that Aesculapian Snakes were indeed one of several species of European snake kept at London Zoo in an "outdoor reptile rock garden".  Aesculapian Snakes were also listed as a species kept at London Zoo on page 5 of the 1928 26th Edition of the ZSL guide book and the 30th Edition as well. These guide books confirm that the Aesculapian Snake was kept at ZSL at the very least between 1928 - 1935.

The Zoological Society of London's Reptile Rock Garden was built in 1928 and London Zoo continued to stock this outdoor reptiliary with British and European snakes until the early 1960s. It's not clear from these guidebooks how many of those years saw Aesculapian Snakes held in captivity at London Zoo. In the 1954 ZSL guide book, and subsequent guide books that followed, the Aesculapian Snake was no longer specifically mentioned as a species kept at ZSL.

Whilst it is widely accepted that the London colony of Aesculapian Snakes became established in the mid 1980's following the deliberate release of several specimens from the former ILEA building, within the ZSL grounds, there are some unsubstantiated rumours, from ex-London Zoo employees, that these snakes were already found at Regents Canal prior to this release by ILEA. Some people have even claimed that these snakes have been in existence in the area since the 1960's, or even earlier, following their escape from ZSL's outdoor reptiliary. I must stress that there is no evidence to suggest that there is any truth to these stories though, and with the possible legal implications, if they were to be true, it's unlikely that the truth would ever be revealed.

1935 32nd Edition, Zoological Society of London guide book

Clinton H. Keeling (1932 - 2007), a former zoologist and historian of British Zoos, wrote many books on the subject of zoology. In his 1988 Clam Publications book 'They All Came Into The Ark' he discussed a Master J C Dendy. It is believed that Master J C Dendy was a young man in private school who "added a few non-existent years to his age" so that he could go to war to defend his country during World War 1 in 1915. Master J C Dendy had a large collection of herpetofauna and before he left for war he donated his entire collection of reptiles and amphibians to London Zoo on 16th July 1915. One of the many species kept within his collection was the Aesculapian Snake. Master J C Dendy was one of many who did not return from the war.  See link here: Malcolm Peaker Zoology Weblog
This is yet further supporting evidence confirming that Aesculapian Snakes were once kept at London Zoo. But even though we know for sure that ZSL did keep Aesculapian Snakes in the first half of the 20th century my research through the ZSL Guidebooks found nothing to suggest though that London Zoo was keeping Aesculapian Snakes, in their private or public collections, until anywhere near as recent as the 1980s when the London population of feral Aesculapian Snakes was established. Things changed when I received help from David Bird who had access to the old ZSL Annual Reports from 1967-1990.

The old ZSL Annual Reports listed exactly which species came into the possession of ZSL each year. From these old reports I have learned that in 1967 one Elaphe longissima, now know as Zamenis Longissimus, was brought in the zoo's collection. Another Aesculapian Snake was also added in 1975. However these reports up until 1977 did not list the full number of species or specimens kept at the zoo, just those added to their collection in each year. From 1977 each ZSL Annual Report listed exactly what species the zoo kept and how many specimens they had. In 1988 the zoo acquired three more specimens of Aesculapian Snake. A ZSL reptile keeper from the time recalls that these three specimens were part of a "dodgy confiscated shipment" and one specimen had most of its tail missing. By 1990 the ZSL Annual Reports listed no specimens of Aesculapian Snake were kept at the zoo in any of their collections. Although we know for sure that the London population of Aesculapian Snakes originated from a deliberate release by ILEA staff, these ZSL reports prove beyond doubt that ZSL did have Aesculapian Snakes within their collections, at vary times, until 1988.


The Aesculapian Snake was once native to the UK  -  Fossil Remains of Aesculapian Snakes found in Suffolk & Essex

In the UK there have been three discoveries of ancient fossil remains of Aesculapian Snake, found in Suffolk and Essex (B.H.S. Bulletin no.50 1994). These fossils date back to the warm end of the Chibanian, or Late-Middle Pleistocene Period, around 129,000 years ago. So although currently considered a non-indigenous species many people have now accepted that the Aesculapian Snake was actually once native to the UK, when the climate was warmer, before being driven south by the arrival of subsequent glacial periods. This topic is covered in the 1998 book "Pleistocene Amphibians and Reptiles in Britain and Europe" by Professor J. Alan Holman. DNA analysis has confirmed that the isolated Aesculapian Snake populations in Northern Europe are proof that the range of the Aesculapian Snake has regularly expanded and contracted slowly over long periods of time when necessary to cope with changes in climate as the Earth has warmed and cooled. See articles here: 1) Relics Of The Europe's Warm Past - Phylogeography Of The Aesculapian Snake   2) Isolated populations of Zamenis longissimus (Reptilia: Squamata) above the northern limit of the continuous range in Europe.

There remains several isolated populations of Aesculapian Snake, found at sites across Europe today, which are relics of the previous vast range of the Aesculapian Snake just 5000 years ago when the climate was warmer than it is today. - See article here: 2005 Action Plan for the Conservation of the Aesculapian Snake (Zamenis longissimus) in Europe - by David Bird & Paul Edgar 

Fossilised remains of Aesculapian Snakes have been found in the UK at three different sites: East Farm, Barnham, Suffolk (discovered in 1994)  &  Beeches Pit, West Stow, Suffolk (TL798719 discovered in 1991)  &  Cudmore Grove, Essex (discovered in 1990). 

One might also consider the possibility that these UK fossils are the remains of ancient feral populations of Aesculapian Snake that either escaped from captivity or were deliberately released, as it is often reported that both the Greeks and the Romans kept Aesculapian Snakes in temples for healing and fertility rituals. However, the Mycenaean civilisation of early Greece (1600BC - 1100BC) never made direct contact with Britain and the Romans did not come to Britain until 43AD, so if the fossils are dated correctly then this hypothesis can easily be ruled out.

Purchase "Pleistocene Amphibians and Reptiles in Britain and Europe" by Professor J. Alan Holman. 

The range of the Aesculapian Snake once stretched as far north as Denmark, which is further north than any of he Aesculapian Snake populations now found in both Wales and England. Until around 6500 BC mainland Britain was joined by land to the European mainland allowing Aesculapian Snakes to travel north and extend their range as necessary when the climate warmed up. So why wouldn't this species have also once been resident in the UK as well?

Whilst Britain focuses its conservation efforts and reintroduction programs on other species including the Sand Lizard, Natterjack Toad and Pool Frog, at sites across the UK, why are we not doing more to protect the three well established and naturalized populations of Aesculapian Snake in the UK? And worse still why are we even considering their deliberate eradication if this species was previously found in Britain anyway and is not only critically endangered in much of its native range across Europe, but is also spreading its range further north as our climate warms?

Should these current introduced British populations of Aesculapian Snake therefore, whether intentionally released or accidentally escaped, now be considered as a reintroduction success story of a lost reptile species now returned to Britain once again? With many specimens of the London population of Aesculapian Snakes having already been poisoned, or captured and taken from the wild by reptile collectors, isn’t it about time this species was afforded the same level of protection by UK law as our other rare herpetofauna?

The fossilised remains of Aesculapian Snake that were found at the Cudmore Grove site in Essex, were one of 14 species of herptile found there. Seven of these species are no longer present in Britain but can still be found in Continental Europe. This further supports the evidence of a once warmer climate in Britain, more suited to Aesculapian Snakes and other herpetofauna. With so many other reptile and amphibian species also being found at the Cudmore Grove site this also supports the evidence that Aesculapian Snakes were one of many species of native reptiles and amphibians that could be found living in the area at that time rather than Aesculapian Snakes being an introduced species from captive specimens brought in from ancient Greek or Roman settlements. In fact all three sites where Aesculapian Snake fossils have been found in the UK also contained fossilised evidence of other species of herptiles that are now only found in Continental Europe.  LINK

It is my hope that one day Natural England and our Government will no longer consider the Aesculapian Snake to be a non-native and invasive species but instead will embrace it as a returned species once native to the UK and afford it the same level of protection under UK Law as our other rare reptiles benefit from.

Does this mean that we should reintroduce all species that were once found in the UK? No, definitely not. Other species that were once found in the UK would no longer integrate into Britain’s current ecosystems without disrupting their delicate balance. But the Aesculapian Snake has found its place in current local UK ecosystems where it can both thrive and fully integrate in harmony with its surroundings. If Aesculapian Snakes were to become widely established once again in Britain they would not become an apex predator but would simply become another piece of the food-chain for local ecosystems.  Having Aesculapian Snakes in areas inhabited by humans can actually be a benefit to man and would serve as a beneficial response to counteract the increase in mice and rats that are now found in abundance around human habitation which is a direct result of man’s behaviour. Due to the lack of suitable Aesculapian Snake habitat in the UK it would be highly unlikely that this species could ever become common in the UK once again. However it could, if allowed, form thriving colonies at many sites across the UK in ideal locations.

The Aesculapian Snake even features on Wikipedia's list of "Extinct Animals of the British Isles".

Sadly as the current UK Law stands any species that has been absent from Britain for more than 10,000 years, since the last ice-age, is considered as a non-native species. Although this is bad news for the Aesculapian Snake in the UK it does open the door to the possibility of licenced reintroductions of Moor Frog, Pool Frog, Agile Frog and European Pond Turtle at some stage in the future. All of which were once found native in the UK well after the last ice-age.

This map shows the range in 2020 for Aesculapian Snakes across Europe. See detailed ICUN Red List map hereSee also European Environment Agency Map

The Aesculapian Snake is one of four species of Rat Snake currently found in 31 countries across Europe. It is known that their range once reached far further north than it does now when the Earth's climate was warmer. Some suggest that this vast range may have been contributed to by escaped specimens from when the Romans kept Aesculapian Snakes during the Roman occupation of Europe. Although some herpetologists claim that there is little or no truth behind the "myth" that the Romans kept Aesculapian Snakes, other historians claim that not only were the snakes kept in temples for rituals and ceremonies but they were also kept in homes as "house snakes" to serve as vermin controllers. (see link here)

In the last 150 years Aesculapian Snakes have gone extinct in five northern countries with Denmark previously being the northern most part of their range until around 1863 when the last of the Aesculapian Snakes in that region died out.  Article 1  &  Article 2

DNA testing of preserved specimens of Aesculapian Snake collected from Denmark in the early 19th Century have confirmed that it is highly likely that these Danish Aesculapians were part of an extended range originating from the Balkans rather than being introduced specimens. The Southern Balkans were a glacial retreat for many reptile species during the ice-ages. And we know that Aesculapian Snakes were present in Denmark from at least 7500BC right up until 1863. See article here: Centuries-Old DNA from an Extinct Population of Aesculapian Snake (Zamenis longissimus) Offers New Phylogeographic Insight - by Morten E. Allentoft, Arne Redsted Rasmussen and Hans Viborg Kristensen

The 2014 paper "The Grass Snake and the Basilisk: From Pre-Christian Protective House God to the Antichrist" by H. J. R. Lenders & Ingo A. W. Janssen discusses how both the Aesculapian Snake and the Grass Snake once had such a successful northerly range across Europe. From Neolithic times both theses species were often found in the close vicinity of human habitation as these egg-laying snakes took advantage of dung piles, regularly kept by man, and used them to successfully incubate their eggs. The article also mentions that in pre-Christian times snakes were revered as signs of deity and it was regarded as a bad omen for any snake to be harmed by man. These snakes were seen as a protector of both cattle and those humans who inhabited the farmland. Once Christianity arrived in Europe during the Early Middle-Ages (5th or 6th Century) many pagan signs or symbols were either abolished or their meanings were changed to fit inline with Christian beliefs. In the case of the snake it went from being worshipped by pagans as a divine protector to being the Basilisk, a symbol of the anti-Christ, and man's attitude towards snakes in Europe was changed for nearly two thousand years and the persecution of snakes began. 

What can done to help the London Aesculapian Snakes?

The biggest threats this small population of wild snakes face are from: a) human persecution, b) collection for the pet trade, and c) a lack of suitable egg-laying sites. 

a) It's human nature for people to fear what they do not understand, and Ophidiophobia, the fear of snakes, is the second most common phobia in the world. Helping people to understand that these snakes represent no danger to humans or their pets, or to any native species other than rodents, is important to reduce the persecution these snakes may face when they come into contact with members of the public. Voicing your opinions and opposing scaremongering and sensationalised stories about these snakes from the media is necessary to change public perception. Directing people to this website can help them understand and appreciate these fascinating snakes.

b) It's essential that we speak out against the collection of these snakes for use in the pet trade. With so few snakes being present at Regents Canal removing just one or two specimens could have a hugely negative effect on the population.

c) The biggest problem these snakes face in London is the lack of suitable egg-laying sites. There has been very limited breeding success in recent years at Regents Canal. Like our native Grass Snake the Aesculapian Snake relies on the heat generated by piles of manure or rotting vegetation to incubate their eggs. The creation of compost heaps in the area would be extremely beneficial to these snakes. With much of the range of this Aesculapian Snake population falling within the grounds of London Zoo it is ZSL themselves that have the greatest opportunity to help with the conservation of this species. This is unlikely to happen unless we can encourage Natural England to accept and embrace the Aesculapian Snake as part of British fauna.

Creating compost heaps along the publicly accessible woodland banks of the canal would provide the necessary egg-laying sites these snakes need, but would also come with the added risk of making it easier for the selfish collection of these snakes for the pet trade. The advice for creating suitable egg-laying sites for Aesculapian Snakes is similar to that for Grass Snakes and any compost heaps created could be done for the benefit of native species too. Compost heaps would need to be a very minimum of 1 M³ in size and at least partially exposed to the sun. For an egg-laying heap to be successful it is important to ensure the rotting material provides the necessary heat and humidity to incubate the eggs. Larger heaps of vegetation are usually more successful than smaller heaps. Compost heaps usually have to be in existence for around two years before snakes start to use them for egg-laying. New decomposable material needs to be added regularly and replenishing is best done in April to May or in October when the heaps are not in use. A good compost heap may be used by several female snakes at the same time laying their eggs together. Some heaps benefit from being partially covered by a tarpaulin or sheet of carpet, which traps the heat, but this may also draw unwanted attention to the heap. Eggs are incubated any time between June and September and it's important that the heaps are not disturbed during these months. Uncovering the eggs, even momentarily, could release valuable trapped heat from within the heap. You can check if a heap is being used by snakes as an egg-laying site by looking around the heap towards the end of August or in September for new snake hatchlings, or in October when the heap can be safely opened to reveal broken and vacated egg-shells. It's possible that larger heaps could also provide somewhere for the snakes to hibernate during the colder winter months so heaps shouldn't be disturbed during this period either. Because female snakes tend to use the same egg-laying sites year after year it is important to replenish heaps yearly or create new heaps close to the old heaps.

Albino and Melanistic Specimens

Both albino and melanistic specimens of Aesculapian Snakes have been found living in the wild in Austria, Slovenia Bosnia & Herzegovina and Italy but these are incredibly rare. However melanistic specimens are not uncommon in the pet trade. There are no records of any such specimens ever being found wild in the UK. In Greece grey morphs of the Aesculapian Snake can also be found. Striped specimens have been found in Pavia, Italy. In Serbia , where their is huge variation in the appearance of Aesculapian Snakes, axanthic / melanistic specimens can be found. Serbian Aesculapian Snakes vary from light to dark morphs, as well as yellowish or even greenish specimens. Specimens exhibiting feint longitudinal stripes have also been found in Serbia.

1) Read 2003 article on first Albino specimen in Slovenia here.    2) Read 2018 article on Albino specimens in Slovakia here.   

3) Read account of striped specimens found in Pavia, Italy.    4) See axanthic / melanistic specimen from Serbia, April 2022.

In 2013 an incredibly rare amelanistic Aesculapian Snake was found in a garden in Austria. It was taken into captivity and is held at the Reptilienzoo Nockalm, in Austria. This image was shared on the "Zoochat" forum. Other photos can be found here on Flickr. Amelanism is similar to albino, however in amelanism there is a complete lack of dark colour pigments as oppose to a total lack of all colour pigments found in true albinos. An account of the history of this snake written in German can be found here. And videos of this snake can been seen here:   LINK 1   LINK 2   LINK 3

In 2014 a wild hypomelanistic colour morph of the Aesculapian Snake was also found in Austria. This specimen was partially lacking black pigmentation and is the only specimen of its kind ever seen in the wild. One photo was taken before the snake escaped. The story was run by Krone Multimedia. See link here.

In 2014 a wild albino Aesculapian Snake was found in the town of Teslić in Bosnia & Herzegovina. The snake was 900mm in length and was found at an altitude of 220m above sea level. To date this was only the 10th albino specimen of Aesculapian Snake ever to be found in the wild in Europe.  See link here

Where can I find wild Aesculapian Snakes? shows records of sightings across Europe including some from both Wales and London.

ARC Trust also shows approximate records for sightings in Wales here: Wales Online Amphibian & Reptile Atlas

Aesculapian Snakes, name and mythology

Zamenis longissimus, the scientific name for the Aesculapian Snake, can be broken down into two parts. The first part "Zamenis" originates from the Greek language, with "Za" meaning "great" and "menos" meaning strength. The second part, "longissimus" roughly translates from Latin to mean "the longest", which refers to these snakes being one of the longest snake species in Europe.

Aesculapian Snakes get their common name from the Greek god Aesculapius / Asclepius, the Greek god of healing / medicine, who was the son of Apollo. Aesculapius was reputed to have mystical healing powers and the ability to transform himself into the harmless Aesculapian Snake.  The skin-shedding of the Aesculapian Snake was seen as a symbol for rebirth and renewal. In Greek mythology the god Zeus killed Asclepius with a thunderbolt as a punishment for accepting money in exchange for resurrecting the dead. Once killed, Zeus placed Asclepius among the stars as the constellation Ophiuchus also known as the serpent bearer.

Aesculapian Snakes were used in ancient temple ceremonies for healing and sexual virility rituals performed by both the Greeks and the Romans. The Greek god Aesculapius is often depicted holding a snake-entwined staff. This staff became a symbol for healing which is still used in modern medicine today and can often be seen displayed outside pharmacies. The second symbol is the Caduceus, a short staff entwined by two serpents often surmounted by wings.

In Serbia, where the Aesculapian Snake is considered native, there is an old expression “Pije ko smuk.” which translates to "He drinks like an Aesculapian Snake".  It's an expression used to describe someone who drinks alcohol heavily. There the Aesculapian Snake is generally known locally as a 'smuk' but it also has another common name of 'kravosica' which translates to ''cow-sucker'. In the past the villagers had the crazy belief that Aesculapian Snakes were parasitic and would bite cattle and drink from their blood. This would result in the cow's milk turning sour and the poor farmers would have no source of income from the sale of the milk. Such ridiculously incorrect information would have lead to the persecution of these beautiful and harmless snakes.  LINK

Aesculapian Snakes on TV

In 2015 the BBC's "One Show" asked me to feature on the program as part of a story they were going to run on the Aesculapian Snakes in London. Following my recommendation they featured the foremost expert on the London Aesculapian Snakes, Will Atkins. At the last minute the BBC sadly chose not to interview myself in the end and instead replaced me with the Greek historian, Simon Chaplin. The finished piece was however both interesting and informative and portrayed the snakes in a positive light. Although once again the knowledge of the true origins of the London Aesculapian Snake colony was withheld unfortunately. Watch the video here:    Watch BBC One Show    LINK 2

London Aesculapian Snake sightings sent to me via email, or shared on social media.

As is often the case with wildlife encounters it's all about being in the right place at the right time when finding as Aesculapian Snake at Regents Canal. Listed below are sightings of Aesculapian Snakes at Regents Canal. Many examples have come from members of the public who witnessed an Aesculapian Snake specimen at Regents Canal purely by chance. I'd also like to give grateful thanks to those that have shared their sightings with me via email. Please let me know if you have a sighting to add:

SIGHTING - 16th May 2022, Chris-26 spotted an adult Aesculapian Snake on the south-bank of Regents Canal. - LINK

SIGHTING - 16th May 2022, Andy Youngs emailed me to report a sighting of an adult Aesculapian Snake on the tow-path of the north-bank of Regents Canal.

SIGHTING - 8th May 2022, Vo Goa spotted a dead 3-4ft Aesculapian Snake at the edge of the towpath by Regents Canal. - LINK

SIGHTING - 11th November 2021, Aladin Aladin observed a 3-4ft Aesculapian Snake crossing the towpath by Regents Canal.

SIGHTING - 13th September 2021, Clive Moss & Joel Dixon found a sub-adult two foot specimen on the north bank of the canal.

SIGHTING - 3rd September 2021, Laura Rivkin saw an adult specimen basking on top of a bush on the north side of the canal.

SIGHTING - 14th August 2021, Chris Roughley, photographed an adult Aesculapian Snake basking just within the grounds of ZSL on the north bank of the canal.

SIGHTING - 9th August 2021, an adult Aesculapian Snake was seen shedding its skin on the north bank of the canal by Peter Bordass.

SIGHTING - 18th July 2021, Theo Uys, saw a snake of around 6ft, believed to be an Aesculapian Snake,  cross the canal tow path on the north bank.

SIGHTING - 15th July 2021, a dead 2ft snake, believed to be an Aesculapian Snake, was found in canal by Charlotte Page. 

SIGHTING - 26th June 2021, a 1.5 - 2 metre Aesculapian Snake was seen , and reported to me, on the north side of the canal, by Laura Rivkin.

IMAGE - 31st May 2021, David Jones photographed two adult Aesculapian Snakes found basking on the south-facing bank of the canal. One specimen was only 2ft in length. LINK

IMAGE - 30th May 2021, Lawrence Hill emailed me photos of an adult Aesculapian Snake found basking on the south-facing bank of the canal.

IMAGE - 2nd August 2020, Lawrence Hill emailed me a photo of an adult Aesculapian Snake (Number 36) found basking within the grounds of ZSL. Lawrence also found a slough along the banks of Regents Canal. This snake, Number 36, had not been recorded since 2012.

VIDEO - On 12th July 2020 an adult female Aesculapian Snake was filmed crossing the bridge over Regents Canal in London and shared by "Upthelondon" on Instagram
See the video here:  Aesculapian Snake on Instagram 

IMAGE - 18th May 2020, 'Alexswe' recorded an adult Aesculapian Snake found on the footpath by Regent's Canal. (iNaturalist)

IMAGE - 18th May 2020, a member of the public sadly sent me a photo of a dead adult Aesculapian Snake found on the footpath by Regent's Canal.

IMAGE - 17th May 2020, Twitter user "No More Lonely Nights@The Old Justice" posted an image of an adult female Aesculapian Snake found on the footpath by Regent's Canal. See image here

IMAGE - 25th September 2019, Chris-26 recorded a sighting of an Aesculapian Snake found by Regent's Canal on October 5th on iNaturalist.

IMAGES - 26th July 2019, a series of photos of an Aesculapian Snake at Regent's Canal were published on Facebook by Andi Roy.  See images here

IMAGES - In 2019, a series of photos of an Aesculapian Snake found within the grounds of ZSL were published by Coryn McGovern, a Horticulturist for ZSL London Zoo.  See images

VIDEO - On 29th April 2019 another Aesculapian Snake was filmed crossing the path by the same bridge over Regents Canal in London by a member of the public, and shared on Twitter.
See the video here:  Aesculapian Snake on Twitter 

VIDEO - 23rd April 2019 an Aesculapian Snake was filmed crossing the path by a bridge over Regents Canal in London by Natalie Tambini, a member of the public, and shared on Twitter.
See the video here:  Aesculapian Snake on Twitter  

IMAGE - 22nd May 2018 - A video of an Aesculapian Snake at Regents Canal was captured by a member of the public, Peter Gallagher, who posted on Twitter to ZSL  See image here

IMAGE - 8th May 2018 - An image of an Aesculapian Snake at Regents Canal was shared on the London Natural History Society Forum on Facebook by a member of the public, Alejandro Labrada.  See image here        

IMAGE - 23rd September 2017 - Another image was captured by a member of the public, Peter Gregor, as an Aesculapian Snake openly crossed the path at Regent's Canal:  See image here

IMAGE - 11th June 2017 - An image was captured by another member of the public, Dimah Hanson, who posted on Twitter asking ZSL if they'd lost any of their snakes?  See image here

IMAGE - 11th June 2017 - An image was captured by a member of the public, David Ponsford, who posted on Twitter asking ZSL if they'd lost any of their snakes?  See image here

IMAGE - 11th June 2017 - An image of two Aesculapian Snakes basking by the canal towpath was shared on Facebook by a member of the public, Paul Cockerton.  See image here

VIDEO - 30th April 2017 - A short video was captured by a member of the public, Webster Forrest, of male Aesculapian Snakes engaging in mating combat in London.  See video here

IMAGE - 12th June 2016 - An image of two Aesculapian Snakes at Regents Canal was shared to BBC Springwatch on Twitter by a member of the public, David Carr  See image here

IMAGE - 5th June 2016 - An image was captured by a member of the public, Damian Samuels, who posted on Twitter asking ZSL if they'd lost any of their snakes?  See image here

IMAGE - 26th June 2015 - An image was posted on Flickr by Julian Tysoe of Aesculapian Snakes within the grounds of ZSL  See image here

IMAGE - 7th July 2015 - An image of an adult female Aesculapian Snakes crossing the canal towpath was shared on Twitter by a member of the public, Eloise Juryeff.  See image here

IMAGE - July 2013 - An image was posted on the website of Anthony von Plettenberg Laing of Aesculapian Snakes within the grounds of ZSL  See image here

VIDEO - 2013 an Aesculapian Snake was seen basking along the edge of Regent's Canal by members of the public. It was filmed and shared on YouTube. 
See the video here:  Aesculapian Snake on YouTube

IMAGE - 29th August 2011 - Simon NL West shared an image of a 5-6ft Aesculapian Snake slough found on the north bank of Regents Canal. See image here

VIDEO - 16th May 2006 - The BBC program "IOLO's Welsh Safari" had a feature showing footage of Aesculapian Snakes living wild around the grounds of the Welsh Mountain Zoo. The first time these snakes had been caught on film. See article here


VIDEO - February 2020 - Using my web page on Aesculapian Snakes as research material Jack Perks, known for his incredible underwater photography, produced a short YouTube film about the Aesculapian Snakes in London, featuring Will Atkins, which was released in February 2020. Sadly the true origin of the feral population of London Aesculapian Snakes was withheld from the film. It was also mistakenly claimed in the film that Aesculapian Snakes have never been kept at London Zoo. Guide books for the Zoological Society of London dating from 1928 to 1935 confirm that Aesculapian Snakes were indeed one of several species kept at London Zoo in an "outdoor Reptile Rock Garden" from at least 1928 to 1935 and possibly as late as the early 1960s when the Reptile Rock Garden ceased to be restocked with European snakes.  

The Aesculapian Snakes in London can be extremely unpredictable and difficult to find and on the day of filming in August 2019 Jack & Will were unfortunately unable to find any of the illusive feral Aesculapian Snakes at Regent's Canal and were forced to use captive specimens in Staffordshire to feature in the film. The film shows how beautifully docile this species can be. Jack's images can be seen here.

Rewilding Britain and Restoring Lost Reptile Species

Harvey Tweats and Tom Whitehurst, of Celtic Reptile & Amphibian, started their mission in 2020 to encourage the rewilding of much of Britain's countryside and to see the re-introduction of lost reptile and amphibian species to the UK. The idea of returning green spaces to a more natural state has seen a huge following of interest from people of all backgrounds in recent years.

In February 2021 Celtic Reptile & Amphibian commenced the process of building the largest outdoor reptile and amphibian breeding facility in the UK and amongst their collection of species are Aesculapian Snakes. Their plans to start re-introducing species that were once found native in the UK back into the wild marks the beginning of a new and exciting chapter for British wildlife. The initial species that they plan to involve in their re-introduction projects are the European Pond Turtle, Agile Frog and the Moor Frog. These are species that could be found living wild in the UK just a couple of thousand years ago before they were driven to extinction by man's actions including the hunting of Pond Turtles themselves as well as the hunting of Beavers that are directly responsible for creating the necessary habitat for amphibians such as the Moor Frog. 

Should these ambitious re-introduction plans get the necessary support in the UK and go ahead then they could be the first step to seeing other lost reptile species, such as Aesculapian Snakes, also re-introduced to Britain once again. At the very least it could start to open people's minds and encourage a more accepting attitude towards the already established populations of Aesculapian Snake currently found in the UK.

Their story has received great interest from the media including The Guardian newspaper who printed an article on them on 10th January 2021. On Friday 5th February Harvey and Tom were featured on Channel 4's lunchtime TV program "Steph's Packed Lunch". They also brought with them European Pond Turtles, Sand Lizards and Aesculapian Snakes that were also featured on the show. The BBC also made their own video which was aired on 6th September 2021.

Celtic Reptile & Amphibian have several Aesculapian Snakes specimens in their care that will hopefully form a breeding population that can one day be used for conservation purposes at some stage in the future. One of the Aesculapian Snakes in Harvey's care originated as a wild-caught specimen taken from the feral Aesculapian Snake population in London at Regents Canal. It was brought to him in 2019 after it was accidentally hit by a bicycle on the towpath by the canal. This male specimen did not take well to being kept in captivity and took a year before it began feeding. This demonstrates one of the many reasons why these beautiful creatures should not be taken from the wild to be kept as pets. Captive bred specimens can be found for sale should anyone wish to keep this species.


Aesculapian Snakes at Regents Canal

Some iPhone 6 footage I filmed at Regents Canal, NW London, of wild Aesculapian Snakes during 2020 and 2021.

London Aesculapian Snakes in Litriature

The 2016 book by James Lowen, "A Summer Of British Wildlife" makes mention of the London Aesculapian Snakes but fails to give any accurate information on the origin of these non-native snakes, claiming "Nobody knows exactly how these harmless mud-green, European serpents reached London but some fingers point towards the adjacent zoo."

See relevant section, Day 97, page 230 here:  A Summer Of British Wildlife by James Lowen

James Lowen has unfortunately made unfounded claims elsewhere that the London Aesculapian Snake population originated from escapees from London Zoo. See LINK here.

The 2015 book "Field Guide to Invasive Plants and Animals in Britain" by Olaf Booy Max Wade & Helen Roy, also mentions the two known populations of Aesculapian Snake back in 2015 on page 218. Unfortunately both populations are again incorrectly blamed on escapes from local zoos.

The 2015 book "Cold Blood: Adventures With Reptiles & Amphibians" by Richard Kerridge, also mentions the two known populations of Aesculapian Snake back in 2015 on page 266. The writings are fair and reported in a positive light.

The 2000 Collins New Naturalist book "Amphibians and Reptiles" by Trevor Beebee & Richard Griffiths, on page 203, mentions the Welsh population of Aesculapian Snakes at Colwyn Bay having been in existence for over 30 years at the time. The book fails to acknowledge the London population of these snakes as few people were aware of their existence at that time.


Research on the Welsh Aesculapian Snakes 2020 - 2022

Worryingly it seems the London Aesculapian Snakes are not the only ones under threat. According to January 2020 Issue 3 Edition of the 'Wales Invasive Non-native Species Group Newsletter' the Colwyn Bay population of Aesculapian Snakes are being radio tagged throughout 2020 & 2021 to help compile data that will be used to build a plan for their control and possible removal from the wild. 

"The Biodiversity and Ecosystem Evidence and Research Needs (BEERN) Programme has provided funding under the KESS Studentship scheme for an impact assessment of the introduced Aesculapian Snake population in North Wales.

This project seeks to develop a widely applicable model system for early invasive species assessment and control planning that will benefit invasive species control efforts in the UK. Through the monitoring of their movements and habitats, the data on snake behaviour and habitat use will feed into an integrated removal plan for the species and contribute to preventing further range expansion and invasiveness. The project began in October 2017 and will continue until October 2021. Snakes will be implanted with radio transmitters between April 2020 and September 2020, and again April 2021 until September 2021."  

27th February 2013 - The Invasive Non Native Species Group Meeting at the Welsh Government Building, Aberystwyth, it was decided that despite the low risk of Aesculapian Snakes spreading or causing any impact on the local ecosystem, they should be considered as a high priority for control or eradication. These narrow-minded bureaucrats also decided that all non-native species should all be treated the same regardless of the low risk they pose and they should not treated on a 'species-by-species' basis.

Radio Monitoring in Wales 2nd June 2021
This snake is a "Management Priority Species" for Wales. Students from Bangor University, under the supervision of Wolfgang Wüster, have been monitoring the North Wales population since 2004 to assess the species’ impact on our native Welsh ecosystem.

Due to licensing restrictions on animal experiments in the UK, Tom Major, a PhD student under Wolfgang Wüster at Bangor University, was finally able to release two Aesculapian Snake specimens back into the wild at Colwyn Bay three years after they were taken into captivity. These snakes have been surgically implanted with radio transmitters that will allow Tom to study their exact movements and behaviour. It is hoped that this ground-breaking work will give a much greater understanding of the secret lives of these shy serpents. LINK    LINK 2
Four more radio-tagged specimens were ready for release within a few days of the original releases. Before radio transmitters were used in this research the monitoring of individual juvenile specimens was done by "visible implant elastomer" marking and the recapture of these specimens allowed positive identification under ultraviolet light. LINK   LINK 2

Early results announced 25th June 2021, from the ongoing radio-tagging of Aesculapian Snakes in Wales by Tom Major, has shown that these snakes move about a great deal. Those specimens being monitored in Wales are proving to spend a lot of time in, under and around buildings, where they're hunting for rodents. They've also been found in meadows and woodland too.

An update on the radio-tagging of the Welsh Aesculapian Snakes on 16th August 2021 by Wolfgang Wüster revealed more fascinating behaviour from the ongoing studies of these snakes. The Aesculapian Snakes living around the Welsh Mountain Zoo have been shown, much like Aesculapian Snakes in their native European countries, to be a synanthropic species, and have been monitored spending a lot of time in the walls and lofts of houses and buildings. It is believed that not only do these snakes hunt rodents in these buildings but they also use them as a dwelling place for safe refuge. A old slough was found tangled around a drainpipe near the top of an urban house, whilst Radiotelemetry showed the snake itself to be somewhere inside the walls of the house.  These studies have also shown the snakes to hunt in woodland-bordered open grassland  too. Although many of the local Welsh people seem to be supportive of these studies and accepting of the Aesculapian Snakes, it seems the biggest issues these snakes face in that area are cars, cats and buzzards. 

By the end of 2021 nine Aesculapian Snake specimens had been radio-tagged as part of this project. So far these studies have shown that June is the time of year when these snakes are most actively on the move. It is believed that this indicates June to be the time of year for male Aesculapian Snakes in Wales to head off in search of females to breed with. Female snakes have also been shown to have another large period of activity in July as they head off to their egg-laying sites, which is often the zoo's dung-pile, and sometimes compost heaps outside of the zoo. Other interesting information from these studies shows these snakes tend to be active for a few days whilst they hunt and then they rest for a further few days after eating, allowing their food to digest. For the first time these studies have been able to confirm that cannibalism can occur within Aesculapian Snakes. After two GPS tags from different snake specimens were found to be spending quite an unusually long time in the same area, outside of the breeding season, it was revealed that the male snake had actually eaten another female snake.

Watch Tom Major's video presentation on his studies of the Aesculapian Snakes at the Welsh Mountain Zoo, 8th November 2021 - LINK

Mirror article 11th May 2022

On 11th May 2022 the press picked up the story and reported on the success of Tom Major's studies on the Welsh colony of Aesculapian Snakes in the Colwyn Bay area. It was hugely refreshing to see the Media, including the Mirror, write positive articles, with largely accurate information, which portrayed these snakes in a positive light. This is in stark contrast to the articles the media printed back in 2014, which were claiming "Killer snakes capable of crushing small children to death are on the loose in Britain! ". It was also the first time I have seen the mainstream media report the Aesculapian Snake as a returned species to the UK, rather than a non-native species. The Mirror article started another debate within the UK Amphibian & Reptile Facebook group, on whether these snakes should be encouraged within the UK or not. Those who are against these snakes are quick to voice their opinions, but sadly many of those who welcome the return of these snakes in the UK seem reluctant to challenge the opinions of the "old school" herpetologists within the group. The debate can be seen here: LINK

The story was run by:   The Mirror    BBC    The Daily Post    Wales Online    Lad Bible    The Sun    The Daily Star    Metro World News


Have you seen an Aesculapian Snake in London?  Do you have information to share?

It is currently unknown how many of these London Snakes still survive in the wild in London. If you are lucky enough to see one yourself please do get in touch with me as I'd love to hear that they are still clinging on in 2021 despite all odds.

Please submit your records of any London Aesculapian Snake sightings to myself at:

This page on my website was originally written in 2011. It has been updated regularly ever since with new and up to date information constantly being added. If you have any information on Aesculapian Snakes that I could add to my website or you have knowledge of the history or future work at the London or either of the two Welsh Aesculapian Snake populations then I'd be fascinated to hear from you.

Lastly, I would like to make an appeal  to anyone considering catching and keeping a wild Aesculapian Snake as a pet. PLEASE DON'T!  It is an absolute joy being able to find, photograph and watch these beautiful reptiles living wild and free in the UK. They have found a niche in our ecosystem that has allowed them to flourish without upsetting the delicate balance  of our environment. It was once suspected that there could be a maximum of 20 breeding pairs in the London population but numbers are now believed to be much lower. Just removing one snake could have serious consequences for the future of this species in London. Many of these snakes have already been caught, and with the high number of rodent traps being used in the area, loss of habitat, and lack of egg-laying sites, these are also likely to have a negative impact on numbers of these snakes. Please just be grateful if you are lucky enough to see one, let it live in peace in the wild, and let other people also experience the joy of seeing them living wild in the UK.

Although considered non-native. the Aesculapian Snake has been protected by UK law since it was revised on 16th March 1992, against being harmed or killed under the 1981 Wildlife & Countryside Act.  This law came into effect from 1st January 1993.   See additional link

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Further images of the feral Aesculapian Snakes I have photographed in London.

Female Aesculapian Snake at Regents Canal, London. July 2021

Female Aesculapian Snake at Regents Canal, London. July 2021

Female Aesculapian Snake at Regents Canal, London. July 2021

Female Aesculapian Snake at Regents Canal, London. July 2021

Female Aesculapian Snake at Regents Canal, London. July 2021

Female Aesculapian Snake at Regents Canal, London. July 2021

Female Aesculapian Snake at Regents Canal, London. July 2021

Female Aesculapian Snake at Regents Canal, London. July 2021

Male Aesculapian Snake at Regents Canal, London. 2020

Male Aesculapian Snake at Regents Canal, London. 2020

Male Aesculapian Snake at Regents Canal, London. 2020

Male Aesculapian Snake at Regents Canal, London. 2020

Male Aesculapian Snake at Regents Canal, London. 2020

Male Aesculapian Snake at Regents Canal, London. 2020

Male Aesculapian Snake at Regents Canal, London. 2020

Male Aesculapian Snake at Regents Canal, London. 2020

Male Aesculapian Snake at Regents Canal, London. 2020

Male Aesculapian Snake at Regents Canal, London. 2020

Male Aesculapian Snake at Regents Canal, London. 2020

Male Aesculapian Snake at Regents Canal, London. 2020

Male Aesculapian Snake at Regents Canal, London. 2020

Male Aesculapian Snake at Regents Canal, London. 2020

Male Aesculapian Snake at Regents Canal, London. 2020

Male Aesculapian Snake at Regents Canal, London. 2020

Male Aesculapian Snake at Regents Canal, London. 2020

Male Aesculapian Snake at Regents Canal, London. 2020

Male Aesculapian Snake at Regents Canal, London. 2020

Male Aesculapian Snake at Regents Canal, London. 2020

Male Aesculapian Snake at Regents Canal, London. 2020

Male Aesculapian Snake at Regents Canal, London. 2020

Adult male Aesculapian Snake at Regents Canal, Lndon. 2019

Adult male Aesculapian Snake at Regents Canal, London. 2019

Adult male Aesculapian Snake at Regents Canal, London. 2019

Adult male Aesculapian Snake at Regents Canal, London. 2019

Adult male Aesculapian Snake at Regents Canal, London. 2019

Adult male Aesculapian Snake at Regents Canal, London. 2019

Adult male Aesculapian Snake at Regents Canal, London. 2019

Adult female Aesculapian Snake at Regents Canal, London. 2019

Adult female Aesculapian Snake at Regents Canal, London. 2019

Adult male Aesculapian Snake at Regents Canal, London. 2019

Adult male Aesculapian Snake at Regents Canal, London. 2019

Adult male Aesculapian Snake at Regents Canal, London. 2019

Adult female Aesculapian Snake at Regents Canal, London. 2016

Adult female Aesculapian Snake at Regents Canal, London. 2016

Adult male Aesculapian Snake at Regents Canal, London. 2012

Aesculapian Snake habitat. The South bank of Regents Canal, London. 2020




This website page is the result of many years of research and field work,  all photographs and text on this page are copyright protected by law and are the intellectual property of Jason Steel. Do not use without my written consent.

Photographs were taken using:

 Canon 7D & 40D cameras and the Canon 70-300mm f/4-5.6IS, Canon 100mm f/2.8IS Macro,  Canon 15-85mm and Sigma 14mm f/2.8 Wide-Angle lenses.