Part 6: Eemian Reptiles and Amphibians in the UK

 

Dice Snake

The modern British herpetofauna is rather impoverished compared to mainland Europe, with many species certainly capable of living and breeding in Britain reaching the North Sea and Channel coasts but going no further. This is due to the separation of Britain from the continent – by the time southern European species had spread north far enough the sea was in the way. However, at least a few species made it to Britain early but then disappeared as the climate became cooler and wetter during the Holocene. As the Channel was formed prior to the Eemian Interglacial the same situation would have applied as the weather warmed up, and the herpetofauna of the British Isles would also have been limited compared to the European mainland.

Among the reptiles as well as the Grass Snake, Smooth Snake and Adder that are resident today there have been found fragmentary remains of at least one, possibly two other species. The Dice Snake Natrix tesselata is a small relative of the Grass Snake and like it feeds on fish and amphibians. The Viperine Snake Natrix maura has a very similar diet but seems to prefer slightly warmer conditions, making it perhaps less likely to be the small Natrix species known from a few Eemian sites. Grass snakes are very fond of using compost heaps and manure piles on farms for egg laying, so they might have made similar use of the territorial middens of the various rhinos,

Lizards like the Viviparous Lizard, Sand Lizard and Slowworm that are resident in Britain today are all known from the Eemian. Other species such as Western Green Lizard or Wall Lizard (both introduced to the UK today) may have been present but whether they got to Britain before the rising seas isolated Britain is not known.

European Pond Tortoise

One reptile that did make it to Britain is the European Pond Tortoise, which is known from several sites. Britain is very marginal for this species and it could only breed successfully when summers were long and warm enough for the eggs to incubate successfully. They also made it to Britain at the end of the last glaciation, but then died out early in the Holocene.

Among amphibians their remains are usually very fragmentary which makes identification difficult. However, the three newt species (Great Crested, Palmate and Smooth) that live in Britain today were certainly present, as were Grass (Common) Frog, Common Toad and Natterjack Toad – as the Natterjack specialises in disturbed habitats and temporary pools the wallows and other excavations by hippos, elephants and others would have made it fairly widespread compared to its status in Britain today. Also present were at least one member of the Pool Frog/ Marsh Frog complex. Pool Frogs were a resident in East Anglia in the Holocene but the last colonies sadly became extinct in the 20^th century, as they were believed to be introduced and were therefore not protected. Today there is an introduction programme for Pool Frogs, but the most widespread and successful introductions are Marsh Frogs, now present at many sites across the south of England.

Another frog species, the Moor Frog Rana arvalis, has a mainly eastern distribution today but has been found from Eemian sites. They were present in Britain in the early Holocene, but then died out.

Finally, fragmentary remains of Green Tree Frogs are also known from the Eemian, and in the south at least might have been widespread in waterside vegetation and scrub.

European Tree Frog

If Green Tree Frogs made it to Britain before the sea rose it is possible that several other European amphibians made it to Britain but have not yet been found as fossil remains. Midwife Toads, Yellow-Bellied Toads and Fire Salamanders are also possibilities and can survive and breed in a British climate today.

Even less likely to leave remains are most invertebrates, so the next section will have to be mainly speculative.

Spain 25: Horseshoe Whip Snake

Horseshoe Whip Snake

Given that the Spanish trip was in November, it is unsurprising that few reptiles were seen. Aside from a Wall Lizard, the only one was a distant view of what appeared to be a Horseshoe Whip Snake, Hemorrhois hippocrepis. The species gets its English name from the horseshoe shaped mark behind the head, and it one of four in the genus. Aside from the Iberian peninsula it is also found in north west Africa. The other species are found across north Africa and through the Middle East into central Asia.

Lizards 14: Rhinoceros Iguana

C.cornuta

The last of the lizards in this series is one of the largest lizards in the Americas, the imposing Rhinoceros Iguana Cyclura cornuta. Originating from the island of Hispaniola, which is shared between the countries of Haiti and the Dominican Republic, plus some nearby islands, it is the species of Cyclura most often seen in zoos, plus many more in private collections.

Lizards 13: Leptien's Uromastyx

U.aegyptia leptieni

Scattered through dry areas of Africa and Arabia are numerous species of herbivorous agamid lizard in the genus Uromastyx. Formerly included in the same genus are at least three species of Saara, which replaces Uromastyx in the Middle East and India. Commonly called spiny tailed lizards, they are mostly large lizards with distinctive thick, spiked tails which they use on defense, either by striking attackers with it or using it to block the entrance to their burrows.

Lizards 12: Common Chameleon

C.chamaeleon

The third of the chameleon species at Bristol is not often seen in zoos. The Common Chameleon Chamaeleo chamaeleon is the “original” chameleon. It has a range that at least formerly included several of the Greek islands, although now it is only found on Samos, and extends all around the southern and eastern coasts of the Mediterranean, extending as far east as Iran. It is also found in southern Spain, Malta and Crete.  Other species of Chamaeleo are found in sub-Saharan Africa, the Arabian peninsula and in India as far south as Sri Lanka. One of the largest is also the species hobbyists are most familiar with, the Veiled Chameleon C.calyptratus.

Lizards 11: Bearded Dwarf Chameleon

Bearded Dwarf Chameleon - in center of picture

While panther chameleons are among the larger species of chameleon, many species have become miniaturised in the course of their evolution and are generally referred to as pygmy or dwarf chameleons. This has happened on at least two separate occasions, resulting in the dwarf chameleons of mainland Africa and the even smaller leaf chameleons of Madagascar. As a result of their small size and limited capacity to disperse, there are almost certainly many more species of these marvelous little lizards than are currently described.

Lizards 10: Panther Chameleon

Female Panther Chameleon

Of all the world’s lizards, chameleons are perhaps the most instantly recognizable. The distinctive eyes, which are extremely sharp – chameleons probably have some of the best vision of all reptiles – can either give good vision in any direction or be focussed on the same target to give stereoscopic vision and depth perception, essential when using their other distinctive feature, the extensible tongue (which can be as long as their bodies), to catch their prey.

Lizards 9: Yellow Headed Day Gecko

The second species of day gecko kept at Bristol is the much smaller Yellow Headed or Neon Day Gecko, Phelsuma klemmeri. Growing to a maximum length of around 10cm, this species is one of the species more widely kept and bred by hobbyists. In the wild it is only known from a total area of under 1000 km² on the Ampasindava peninsula in north west Madagascar. As a result of its limited range, where it is only known from two regions, it is currently classed as Endangered on the IUCN Red List.

Lizards 7: Utila Iguana

Currently the second largest species of lizard in the Bristol Zoo collection, the Utila iguana Ctenosaura bakeri is also one of the most threatened, as it is currently classed by the IUCN as Critically Endangered. Part of the reason for this is its microscopically small range – it is confined to around 8 sq.km of mangrove swamp on Utila island, off the north coast of Honduras. There are currently 15 recognised species of Ctenosaura, with a natural distribution ranging from Baja California and Mexico south to Colombia, although 2 species have been introduced to Texas and Florida.

Lizards 6: Round-Nosed Plated Lizard

Gerrhosaurus major

Of the larger lizards in the Bristol Zoo collection, one of the more distinctive is the Round-Nosed Plated Lizard, Gerrhosaurus major. Also called the Sudan Plated Lizard, Western Plated Lizard, Rough-scaled Plated Lizard, and other names as well, it has a large range across most of eastern and southern Africa. 

Lizards 5: Solomon Islands Skink

Adult Corucia with juvenile

One of the more unusual, as well as larger, lizards on show at Bristol is a family group of the Solomon Islands Skink Corucia zebrata. Unfortunately, members of the public all too often walk by their enclosure as they tend to be secretive and immobile during visiting hours, often inside hollow cork tubes or resting on an overhead beam in their enclosure. This is a loss for the visitors, as they have one of the more complicated social structures and lifestyles of all lizards.

Lizards 4: Green Tree Monitor

Juvenile V.prasinus

Turning from desert living vegetarians, the subject of this post is an insectivorous species from the rain forests of New Guinea. The Green Tree Monitor Varanus prasinus is widely distributed in rain forests across the island, but as it spends all its time in the canopy it is not seen frequently unless a tree is cut down.

Lizards 3: Chuckwalla

Common Chuckwalla

Sharing the enclosure with the spiny lizards is a breeding group of Common Chuckwalla, Sauromalus ater. This is the most widespread species, ranging over rocky desert areas of much of the south western USA and Mexico. There are four other species, three on islands off the coast of Baja California and Mexico, which are classed as either Near Threatened or Endangered, mostly as a result of their limited range rather than any specific new threats. The remaining species, the Penisular Chuckwalla S.australis, is classed as Least Concern , as is the Common Chuckwalla.

Lizards 2: Blue Spiny Lizard

Blue Spiny Lizard

One of the more obvious lizards as you enter the reptile house at Bristol Zoo are the various members of a colony of Blue Spiny Lizards, Sceloporus serrifer cyanogenys. Also known as swifts or fence lizards, there are more than 90 described species of Sceloporus found in North America south through Mexico down into northern South America. There is a certain amount of debate around the taxonomy of the various Sceloporus species – some seem to intergrade with others and several species are divided into multiple subspecies.

Lizards 1: The Gila Monster

The first lizards that a visitor to Bristol Zoo will encounter are two young Gila Monsters (Heloderma suspectum) as they pass through Twilight World. Unfortunately, although these are fascinating animals, most visitors walk straight past as they are not exactly the most active of animals, in fact they generally behave as though they were stuffed. However, when readers of this blog next see an exhibit, I hope they will at least check them out.

Book Review: Tuatara: Biology and conservation of a venerable survivor by Alison Cree

There are very few species of small(ish) reptile which are famous outside their native range unless they are venomous or brightly coloured, but the Tuatara Sphenodon punctatus of New Zealand is certainly among that select number. Their fame is due to their being the sole survivor of a unique lineage of reptiles separate from the turtles, the archosaurs, and the lizards, although they are most nearly related to the last, although since they split from the common ancestor with the lizards well over a quarter of a billion years ago even that is not close. The book reviewed here is a summary and survey of the whole of tuatara-related research, and covers not just the biology and ecology of the living animal, but its evolutionary history, interactions with humans, and their past, present, and future conservation status.

Nature of Corsica 8: Reptiles

P.tiliguerta male

There are of course many species of reptiles on Corsica, but as this was a mainly bird and botany focussed holiday we did not go seeking them out especially. Despite this, we found at least three species of lizard, including the endemic Tyrrhenian Wall Lizard Podarcis tiliguerta. This was the most widely seen of all the lizards we found, occurring from sea level up to altitude, and they were obvious whenever the sun was out and they could bask.

P.tiliguerta

Quest for the Wild Canary Part 4: Reptiles and Amphibians

Tenerife Lizard

Reptiles of various species are usually good at colonising islands, and the Canaries are home to a diverse range of endemic lizards. There are no native snakes, and at present no native land tortoises, although fossil; ones are known. It is probable that in the past various species of sea turtles also nested, but today they are only seen at sea. The most common of these is the Loggerhead Turtle, Caretta caretta, which also breeds in the Mediterranean. There are even a few reports of Leatherback Turtles beaching on some of the eastern islands, but no proof of nesting or nesting attempts.