Froglife

Leaping forward for reptiles and amphibians

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What our animals are doing this month….

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December is a quiet month for British amphibians and reptiles. All of our native species brumate during the winter, meaning they are dormant with occasional periods of foraging during warmer spells. Amphibians and reptiles overwinter in different habitats, but warm, safe spots such as log piles and compost heaps are often popular choices.

Male common frogs may choose a riskier overwintering strategy. They sometimes decide to overwinter at the bottom of a pond, buried into the mud. This can be a good option as they are unlikely to be disturbed or predated upon, however it can be very dangerous if oxygen levels get too low. Frogs can absorb oxygen through their skin underwater and can tolerate very low levels of oxygen, but they will die under anoxic conditions. However, if there are native oxygenating plants in the pond, then this should ensure sufficient oxygen flow.

Common frogs can also survive if a pond partially freezes, but not if it freezes entirely. As a general rule, ponds with a maximum depth of at least 60cm are safe, but any shallower and there is a high risk of it completely freezing over.

Cold Weather Advice

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To ensure the survival of amphibians during the colder weather, here are a few steps that you can take to support them in your own gardens. 

First, if you have a garden pond, periodically and gently melt any ice on the surface (a hot cup or pan will do the trick!) to promote oxygen exchange. This will allow amphibians which have migrated to the pond to survive in the water beneath the ice and prevent winterkill. Winterkill is where toxic gases released in the pond through natural decomposition of dead leaves cannot escape from the pond due to the layer of ice and the water becoming deoxygenated.

Second, you can try floating a small object e.g. tennis ball, in the water which prevents ice formation. However, this only works in moderate frosts and in severely cold weather, breaking the ice is the only option. Third, provide piles of leaves or areas of dense vegetation and scrub close to your garden pond as this will provide areas for amphibians to take refuge during periods of cold weather. If you have frog spawn, the upper portions may freeze, but the spawn which is underwater should survive. However, if you have a very small pond and/or it is shallow and prone to freezing throughout, you can temporarily place your frog spawn into a bucket of water and place in a garage, or similar place, out of the freezing conditions. Once the cold weather has passed, ensure that you return the spawn to the original place within the same pond to allow it to continue to develop.

For further advice on this topic, please visit our FAQ pages:

If you find any dead amphibians, you can register them with our friends at the Garden Wildlife Health project.