We all know that mammals such as squirrels and hedgehogs hibernate for the winter and in the wider landscape of the Northern Hemisphere, other species such as bears are also another group of animals that often come to mind when people think of hibernation. However there are other groups of animals that also disappear for the winter. How many of you have found a frog or a lizard in the winter? Hopefully none as they should all be hiding in their frost-free refugia, although climate change threatens this behavioural balance.
Reptiles and amphibians are ectothermic, meaning they regulate their body temperature based on the surrounding environment. Calling them ‘cold-blooded’ is an insult and doesn’t really do them justice. In terms of hibernation, yes, amphibians and reptiles (at least in temperate regions) do hibernate. This tends to be somewhere cool (so their metabolic rate it low) and damp for amphibians that’s also safe from predators – the last thing you want to happen to be eaten as you sleep. Refuges may be in the mud at the bottom of ponds and lakes but also likely to be on land such as within a log pile or a natural crevice. Reptiles tend to hibernate in similar locations although all of their hibernation sites are terrestrial. This means that you can sometimes find predator and prey hibernating together, which is an unusual amnesty to ensure that they survive the winter.
The area where a amphibian or reptile hibernates is called a hibernaculum and these can be constructed (such as the example of the wood pile) to promote hibernation in these areas. This can of course cause issues when people then come to burn the wood for fire on nights such as Guy Fawkes Night (5th November, celebrated in the UK) as the wildlife that has decided to hibernate within accidentally becomes a casualty. As that time of year approaches, if you are building a bonfire, please check it for the presence of amphibians, reptiles and mammals which may be seeking shelter for the winter before lighting it up.
You may have heard the time brumation used before. This generally refers to captive reptiles that are from more tropical climates, which are artificially cooled to help trick their bodies into thinking it is becoming time to breed. The animals will still be active but their movements will be slower (due to a slower metabolism) and therefore their food intake will be reduced too. The term should not be applied to wild populations of reptiles, especially those in temperate climates as they do genuinely hibernate. It’s easy to understand how confusion about these two states of dormancy have arisen.
In the UK, reptiles and amphibians will start to begin their slumber in October with them emerging in February/March time depending on the species and their weather preferences. Amphibians tend to be the first to return to normality with toads migrating to their breeding ponds en masse. Reptiles are generally first seen in March but there are always exceptions, some individuals are just more keen than others to get out there and enjoy spring as it comes into bloom.
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