Loss of Frogs

[gardengnome]

I have a deep pond at the bottom of my garden and have always had lots of frogs and a good quantity of spawn. The garden is generally not very tidy leaving lots of places to over winter for all wild life. Last winter the pond froze over as usual but this spring there is no sign of any frogs! Has anyone else experienced a mass loss like this? Do they eventually come back?

[nightshade]

I had no bodies so I assume the resident Grass Snake had eaten them all.
Although I have had three clumps of spawn this year I have no Frogs in the pond. There are several Toads wandering about but only the one very early string of spawn has been laid

[Dogghound]

Where in Britain are you?
do you have newts?
have you experienced any change in water quality?
have any other ponds been created local to you?
or has any significant habitat been lost locally?
Have you added fish?
Have you found any dead frogs?

Frog breeding pond selection can be extremely complex and small changes can sometimes make a large difference. Its unlikely that a grass snake is the problem, predators dont usually put that amount of pressure on prey so that they wipe them all out. Most gardens probably dont have grass snakes anyway especially if you are in the North, where they tend to be more selective of their habitats. A more worrying possibility is one of the fungal diseases such as Chytridiomycosis.

[gardengnome]

Thanks for the replies. I live in East Yorkshire. I did have one frog body in early November. I haven't seen any snakes. During the very cold spell, I lost 2 carp that had been in the pond for over ten years. As a precaution against disease, is it worth cleaning out the pond and starting again?

[Dogghound]

The fact that you have fish in the pond alters it slightly. Frogs and fish tend not to share the same diseases so because a fish has a disease doesn't mean the frog will get one. What is likely to have happened is that the pond has been frozen over winter for a prolonged period this has resulted in a loss of oxygen, the presence of fish on top of this will have used up further amounts of oxygen (directly and indirectly). The fish are likely to have died as a result of this oxygen deficiency over the winter. Frogs hibernating in fish ponds tend to suffer a high rate of mortality for this very reason. I assume your pond is turbid and you cant see any frogs in the bottom?

I suspect that your frogs may have died or another better breeding pond without fish may have been utilized by them in the local area. Without being there you can only speculate.

[King Edward]

It sounds odd that in one year you've gone from having lots of frogs and spawn to having none - presumably the fish have been in the pond for a while and there haven't recently been any major changes to the pond.

It might be that they've gone to a more suitable pond elsewhere, but why all go at once?

It's normal for ponds to freeze over the winter, so that shouldn't necessarily cause a problem. One of our ponds here, which is about 25 sq m and 2' deep, was frozen for ages like everywhere else, but all or almost all the goldfish survived. I did find 2 dead frogs, although it's not a pond they usually breed in anyway and that could just be a normal level of winter mortality.

How many fish do you have in the pond?

I wouldn't have thought cleaning out the pond was a good idea, certainly not on the off chance that it might prevent disease. You don't even know that the frogs died in the pond - as suggested previously they might just have moved elsewhere. I don't think all the frogs hibernate in ponds anyway, so I don't think the whole population would likely be wiped out that way.

If your garden and pond provide good habitat, it's very likely that they will be recolonised by frogs before too long - perhaps by dispersing froglets later this year, assuming that all your frogs actually have gone from the garden rather than just breeding elsewhere.