Steve's Herpetological Blog

An insight into the life of Steve, his research and the many books he reads


#SciFri: Colour polymorphisms in amphibians and reptiles

Field guides are a great way to identify wildlife whether it be in the field or from photographs. I have a large number of them that make up the core of my reference library for countries I’ve visited or I’m involved in projects with. However they have one fatal flaw, they’re unable to display the complete diversity of patterns and variation in colours seen in wildlife. They tend to focus on the most common colouration, which is fair as these are the ones you’re most likely to find in nature whilst out and about or conducting a survey. The issue starts when you have a common species that is unusually coloured, which can then lead to it being misidentified as something else.

I’ve seen a few rare colour abnormalities (such as the xanthochromic frog pictured below), in the common frog before. Thankfully I recognised the individual as a common frog but not everyone might. Some may think that it was an exotic species that had escaped captivity or maybe that it’s colouration was linked to some form of disease. Recently I’ve submitted a small number of natural history notes to various journals, documenting the behaviour and ecology of amphibians and reptiles. Two of these are linked to colour abnormalities in fairly common species, abnormalities that are not seen very often and would certainly cause confusion to the untrained eye.

A xanthochromic from photographed in Cambridge in 2014

Where am I going with this I hear you ask. The possibilities are endless when it comes to polymorphisms in amphibians and reptiles thanks to the structure of their skin and how they derive pigment. They have a number of different types of cells which all contribute a different colour, the removal or addition of these leads to the variation we see in their normal colour ranges as well as in abnormal colouration such as melanism or albinism. So why does this matter? With the recent lockdown and people looking closer at the nature they have around them more closely, a number of polymorphic amphibians and reptiles have been posted online, some of which have never been recorded in those species before.

With a small team of people, we’re working to document and record all of the colour polymorphisms that have been observed in the herpetofauna of the British Isles. The aim of this is to help bring all of the available information to synthesise a review, for the first time, to help prevent further confusion and to also assess which colour polymorphisms affect which taxonomic groups/species the most. Some of these such as albinism are usually associated with a higher mortality rate as the affected animals lose their camouflage and leucism can be associated with neoteny in newts. We also want to include a definition of each abnormality, the causes and how to diagnose affected animals. This should help to clear up any confusion.

Hopefully all goes well and the project will be a success, leading to the publication of the review in a relevant journal. When it is, I shall share it here for you all to enjoy. If you’ve found an interesting looking frog or snake (for example) on your travels, please do tweet me (@stevoallain) so that we can try to work out what is going on.

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