This week at gardenersworld.com we've received lots of letters, emails and blog comments from people who have found dead frogs in their pond.
This week at gardenersworld.com we've received lots of letters, emails and blog comments from people who have found dead frogs in their pond. I've not seen my rescue frogs since October – I'm hoping they’re tucked up safely in the compost bin. But others haven’t been so lucky.
I asked Jules Howard at Amphibian and Reptile Conservation (ARC) what was going on. He explained that because male frogs often lie dormant at the bottom of ponds during winter, they’re prone to dying when the ponds freeze over. This phenomenon - called 'winterkill' - is relatively common, but has been more prevalent this year due to the length and severity of the freezing weather.
Frogs slow down their metabolism when lying dormant, and breathe through their skin. They can survive if the pond freezes over - especially in ponds with lots of plants growing in them, as plants can still photosynthesise under ice and produce oxygen. But if there aren't sufficient oxygenating plants growing in the pond, if it contains lots of leaf litter (which releases noxious gases as it breaks down), or if snow covers the pond and prevents the plants from photosynthesising, gases can build up in the pond and kill the frogs.
ARC suggests doing the following: make a hole in the ice by leaving a pan of hot water on the surface, allowing the base of the pan to melt a hole. Then leave a plastic ball in the hole overnight, and remove it the following morning when the pond surface has refrozen. This enables noxious gases to leave the pond. ARC also warns against smashing, or pouring hot water on the ice, or adding chemicals (particularly salt). All of these methods can cause serious damage to pond life.
Sadly this is all too late for many of our frogs. But now the ice has melted, give your pond a bit of an MOT: clear away leaf litter and invest in some plants to help keep your pond healthy for your frogs, toads and other pond life.
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