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.