Winter Feature Where do frogs go in Winter? By Jim Foster - Conservation Director As the days get shorter, we’re often asked “Where do frogs go in the winter?” Like all amphibians, common frogs are “ectothermic” – that is, they can’t generate their own body heat and instead their body temperature depends on that of their surroundings. Because of their physiology, they become less active as the temperature reduces. Winter poses a particular problem – it’s too cold for frogs to be active, so they need to find somewhere to sit it out. In Britain, common frogs largely hibernate on land. They usually find somewhere underground, or tucked inside a structure that sits on the ground surface. Hence, frogs might overwinter in a mammal burrow, or inside a compost heap. The important thing is that it’s a place where the frog will be buffered against extreme cold, and won’t lose too much water. Having permeable skins, frogs are at risk of drying out if they spend long in a place with no moisture. Some adult male common frogs spend the winter in ponds, secreted among leaves and mud at the bottom. This is a risky strategy, as smaller ponds can freeze over and frogs can sometimes die through a lack of oxygen. But clearly for some frogs the benefit of being first in the pond when females arrive in spring, means the risk is worth taking. Outside gardens, common frogs often hibernate in larger ponds and those with some inflow, which means freezing is less likely. Hibernation ends when the temperatures start to rise again. For adult common frogs this triggers a rapid exodus from their hibernation quarters to breeding ponds. That’s normally February to March across much of Britain, although there is wide variation depending on local weather conditions.
Winter Feature
All British amphibians and reptiles hibernate, though there are differences in where, when and how they spend this challenging winter period. Indeed, “hibernate” may be a slightly misleading term. Some scientists prefer the term “brumation”, to indicate that the animals simply enter a period of low metabolic function and activity, but not in
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the way that mammals overwinter in a very deep sleep. Hence reptiles and amphibians may in fact be active intermittently during hibernation – studies show they adjust their position slightly through winter, and on warmer days they can emerge from hibernation for brief periods of activity. In some areas, newts and frogs spend the winter in ponds and simply lead a slow-moving existence before spring speeds things up. As our climate changes, amphibian and reptile hibernation will be affected. There is evidence that the hibernation period is shortening, and animals may be more
