Frogs, ponds and winterkill

by Kate Bradbury

Two feral pigeons have taken to having a daily bath in my pond. I doubt this will please my frogs, but there's no danger of any ice forming if they continue splashing about in it.

One of Kate's frogs. Photo taken by Julie WatsonIn January I blogged about 'winterkill', after letters, emails and blog comments flooded in from gardeners who'd found dead frogs in their ponds. One commenter, Wishful Thinker, suggested I blog about winterkill before winter, so people can take action to prevent it happening again. So I have:

Winterkill can happen when ponds freeze over for a long period. Noxious gasses build up and literally suffocate any frogs which happen to be there. Frogs (usually males) often choose to spend the winter lying dormant at the bottom of ponds, where they slow down their metabolism and breathe through their skin. They can survive if the pond freezes over, but only if it has oxygenating plants growing in it (plants can still photosynthesise and produce oxygen under ice), or it has very little leaf litter. If there aren't sufficient oxygenating plants in the pond, or it contains too much leaf litter (which releases noxious gases as it breaks down), or snow covers the surface and prevents the plants from photosynthesising, gases can build up and kill the frogs.

To prevent winterkill you need to create a hole in the ice so noxious gasses can leave the water. I shouldn't need to do so this year, as two feral pigeons have taken to having a daily bath in my pond. I doubt this will please my frogs, but there's no danger of any ice forming if they continue splashing about in it. If you don't have pigeons to do the job for you, Froglife suggests doing the following: place a plastic ball in the pond before it freezes over and remove it once a layer of ice has formed. If the pond has already frozen, make a hole by leaving a pan of hot water on the surface, allowing the base of the pan to melt the ice. Froglife 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.

Adding oxygenating pond plants will help maintain oxygen levels in the pond, even under ice. Autumn is a great time to give the pond a clear out, removing leaf litter and other debris. This will keep your pond healthy for frogs, toads and other pond life, and hopefully ensure our frogs make it through the winter, ready to give their populations a good boost in spring.

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Talkback: Frogs, ponds and winterkill
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Gardeners' World Web User 25/10/2010 at 08:49

I leave the pumps in my two ponds running all year round. In late Autumn the pumps are raised onto up turned planting baskets and put back down to the bottom in Spring, as soon as the water temperature rises. The water has always got a clear bit under the water falls, and they look spectacular when ice forms in them and on the adjacent plants. Both ponds have a fairly high stocking rate of healthy, happy fish which produce young, and they are also home to a multitude of frogs that patrol the garden during the summer keeping the slugs under control. The advantages of ponds in gardens are many, the diversity of insects that are attracted to them is wonderful, if you haven't got one , get a spade and start digging.

Gardeners' World Web User 27/10/2010 at 21:29

help i have been invaded with frogs & newts in my garden I dont want them as one I am terrified of them secondly my dog keeps trying to bring them in, please help me

Gardeners' World Web User 01/11/2010 at 10:04

Hi Heather, I spoke to a frog expert about this and he suggested creating more hiding places for your frogs and newts, such as piles of logs and stones, areas of long grass and dense areas of foliage. You won't see them nearly as often and they'll be able to hide better from your dog, too. Hope this helps. Kate

Gardeners' World Web User 11/11/2010 at 19:31

Bradley's garden - Herons visit garden ponds very early in the morning, often before daybreak to feed on fish & frogs. Going un-niticed, as they fly off before we get-up & look out of the window. Unless you are 'lucky' enough to live close to a river with Otters. As these have been known to take fish from garden ponds. A grill is probably the way to keep your fish safe.

Gardeners' World Web User 16/01/2011 at 15:12

Hi, I have just taken about 18 dead frogs out of my pond since the ice has melted, and a number of baby frogs, before this winter the poulation was thriving, I am really concerened that I have lost the entire male popoulation. Just wanted to know if all the males sit at the bottom and will the population recover from such a huge loss. I have also lost 16 of my gold fish and a carp (ice and a heron), I only have 4 gold fish left. Should I restock or will they reproduce. (I did try and keep an opening on a daily basis but it seemed to start freezing over as soon as it was opened!)

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