Garden Frog In frozen pond

[Andy]

Hi, I have a small garden pond and this winter has been bad and today it froze the pond over badly, Now having supported my frog and toad community for over 7 years I now have the suprise of finding a frog still in it. He was struggling under the ice, so I broke it and let him breath i asume. Now does anyone here have some advice as to what to do? do you have any tips to stop the pond or a part freezing over? Personaly I want to bring the little chap into the house but the wife says no way

Andy

[John]

Generally it's a bad idea to break the ice on the pond. The pond still gets air exchange. Common frogs (Rana temporaria) often hibernate in the mud at the bottom of ponds, even when the pond freezes over.

If you want to try and keep the pond somewhat ice-free, float a football or something in it (soccer ball to Americans).

[tess]

Can you explain how this works - I'm concerned now that I'm doing the wrong thing as I have been clearing the ice from the pond. Last year it was the first winter of our pond on the allotment and I didn't clear it and had the hideous experience of going up once the weather warmed up and finding 6 dead frogs floating on the surface of the pond. This year I've been up and cleared the ice several times - previously there was no evidence of the frogs, but today the ice was 2 1/2 inches thick and as I removed it two frogs swam about and some others were just under the surface and much more lethargic. Now I'm concerned I've done the wrong thing and disturbed them whilst they were hibernating. I've put things on the surface of the pond in the hope that they will stop or reduce freezing but the forecast is for seriously below zero temperatures.

Any more info or links would be great.

Thanks

[BEETLE]

I have often seen common frogs moving around under the ice on garden ponds, I have even known them to spawn before all the ice has melted. Ice forms on the surface of ponds because water is at its greatest density at about 4 degrees C. One of the dangers of removing ice is that unless you replace the water the pond gets shallower increasing the risk of freezing the water to the bottom, killing the frogs.
I have had frogs die in a frozen over garden pond, there was a lot of spruce needles in the pond and I think that as they decayed the either took out too much of the oxygen, or judging from the smell, produced hydrogen sulphide.
After this I used to put a ball on the surface to try to keep a hole open and when this failed I would use some warm water to melt a hole every few days just to allow some gas exchange, I was never certain it helped but it did seem to stop the frogs dying. Frogs have hibernated in ponds for a long time in this country without human help and I guess they are pretty good at it.

[John]

When the ice forms on a pond, it actually helps to insulate the water of the pond from the extreme temperatures above the ice/at ground level. When you break it you remove this insulation suddenly and the pond's overall temperature will drop, relatively speaking, rather sharply. For a small pond this can help kill hibernating frogs in and of itself, and shock any other animal life in there too. The effects are more pronounced on small ponds. If you want to know more about this, search for the words thermocline and ponds.

Assuming you break the ice, any frogs "freed" are then exposed to the sub-zero temperatures your ice was protecting them from. British frogs don't have any protection against freezing, so you could be doing more harm than good.

Regarding the frogs under the ice, think about it - if they were suffocating don't you think you'd already be finding bodies? Another point is that severe winters kill frogs. Fact of life. This either occurs because of prolonged freezing conditions (British frogs simply can't withstand conditions like this so huge numbers die each winter), or because the frogs didn't build up the reserves needed to last the winter without food.

The frogs that hibernate in a pond are taking a measured risk of dying during the winter in the hope that (a) they are in a safe environment with fewer predators and (b) they won't have to migrate to their breeding pond in the spring time, thus potentially saving energy for breeding and getting first pick of mates.

[tess]

Hi there,

Thanks for your responses. i think part of the problem is that our pond is near some trees so no matter what I do I can't keep all the decaying vegetation out so it's probably this combined with the freezing which creates problems. I think I need to make sure there's a hole in the ice to ensure there's enough oxygen in that water for the frogs but not disturb things so much and risk the water temperature dropping. I have put some plastic balls and objects floating on the water so it should be easier to remove these to enable oxygen to get in. the pond it pretty deep and there's a good layer of mud in the bottom so hopefully they'll be Ok down there and the water level shouldn't be a problem.

To be fair, despite last year's fatalities there was no shortage of spawn in the pond this spring and we seem to have quite a healthy population, but I was hoping to avoid the grizzly task of fishing out the bodies this last yea.

[John]

You're right about the decaying vegetation - too much can cause problems as it breaks down and with little surface area for gaseous exchange.

[antoinetteolesen]

When the ice forms on a pond, it actually helps to insulate the water of the pond from the extreme temperatures above the ice/at ground level. When you break it you remove this insulation suddenly and the pond's overall temperature will drop, relatively speaking, rather sharply. For a small pond this can help kill hibernating frogs in and of itself, and shock any other animal life in there too. The effects are more pronounced on small ponds. If you want to know more about this, search for the words thermocline and ponds.

Assuming you break the ice, any frogs "freed" are then exposed to the sub-zero temperatures your ice was protecting them from. British frogs don't have any protection against freezing, so you could be doing more harm than good.

Regarding the frogs under the ice, think about it - if they were suffocating don't you think you'd already be finding bodies? Another point is that severe winters kill frogs. Fact of life. This either occurs because of prolonged freezing conditions (British frogs simply can't withstand conditions like this so huge numbers die each winter), or because the frogs didn't build up the reserves needed to last the winter without food.

The frogs that hibernate in a pond are taking a measured risk of dying during the winter in the hope that (a) they are in a safe environment with fewer predators and (b) they won't have to migrate to their breeding pond in the spring time, thus potentially saving energy for breeding and getting first pick of mates.

John, I have a cement garden pond (6' x 6') just under 2' deep. It is now frozen over and there were quite a few leaves in it as I didn't know about the vegetation problem. I have 4 bullfrogs in there (about 6" long) and wonder if I should break a hole in the ice? Also what do you think about the "Pond Breather" or any type of pond heater? Thanks, Antoinette

[John]

Not knowing where you live exactly makes it hard to answer that. 2 feet deep is very shallow for a pond - I would not be surprised if that was prone to freezing solid in most temperate countries. I would try the floating ball solution first to see if that helps (doesn't work on ponds that have thick ice on them though).

Looking at those products from a nature pond point of view, it really depends on how much they heat the water. However it seems like they only keep a small area ice-free, and if this is the case I'm all in favour of them but I advise you trial one before leaving it in there permanently.

[RHD]

I have a half barrel water feature with a couple of water lilies and a fountain. The half barrel is about 3' wide by 18 to 20 " deep. In this three large frogs have decided to live. At first I couldn't figure out how they got in but then one day I saw one hop out and then a little while later, hop back up the side again from the grass. Those guys really can jump.
Last spring, after much croaking and splashing about, there were two blobs of spawn and they all hatched but very few tadpoles grew legs and made it out. I think maybe the big frogs ate them as I never saw any corpses.

With the unusually cold weather for Central London, UK, I have been worried the big frogs are running short of oxygen in such a small amount of water as I have seen one up at the surface trapped under the ice which is quite thick. This is unusual behaviour as they don't usually surface at this time they hibernate at the bottom and I don't see them for another month or so. I leave the little fountain off over winter it is not up to prolonged use so I only have it on a few hours a day when I'm in the garden in the summer.

I melted a couple of holes five or six inches across in the ice with hot water (keeping it well away from the frog) as I have heard breaking the ice by impact can cause shock waves which can kill fish. I'm glad now I did it this way after reading what you said about the ice keeping the temperature up.

Now I have made a sort of floating device out of tin foil and a tea light. The idea is that the tea light heats up the tin foil and melts a hole in the ice hopefully leaving a small hole to allow some oxygen in but 95% at least of the surface will remain frozen. I hope this strikes a medium between the ice keeping the frogs warm and the hole giving them enough oxygen. I'll let you know how it goes.

[Will]

hi guys, I am new here, found the site when searching for advice on whether or not to break pond ice.

I would say to be safe DO make a hole in it. I've just found 15 dead frogs (and a dead goldfish) in my tiny (smaller than a bathtub) pond. It has always been very popular with frogs, but I never imagined there were that many hibernating in there.
It could have been the cold that killed them, rather than lack of oxygen, as such a small body of water loses heat more rapidly than a larger pond. However, I am tending towards thinking it was lack of oxygen resulting from the fact there were so many of them, as well as two fish, in such a small space. There is also a fair bit of decaying vegetation in the pond, which I hear eats up oxygen.

If you have a similar situation in your pond - crowded, fish as well as frogs, decaying vegetation or silt at the bottom, lack of oxygen generating underwater foliage - then definitely melt or gently break the ice.

I am pretty sad about my poor frogs I hope the species as a whole hasn't suffered to greatly with this cold winter here in the UK

[Andy]

Thanks