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Frog Spawn - Why Does it Disappear Overnight?

By: Dr Gareth Evans - Updated: 16 Apr 2017 | comments*Discuss
 
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Q.

I have a small "frog pond" (no fish) that for 15 years or so has had spawn/tadpoles/frogs in it, very successfully. But, over the last three years a mass of spawn appears, usually about mid February, lays about for seven days or so then overnight disappears, leaving not a trace!

The pond has plants, the water is clear and there are an abundance of miniature shrimps and some snails, nothing else to my knowledge has changed over the years. Any idea what or who is pinching my spawn and what can I do about it!?

(Mr Nick Birnie, 3 December 2008)

A.

How very annoying for you! Without knowing a lot more about the layout of your garden and its surroundings it’s a bit difficult to be too sure, but there are a few possible culprits which spring to mind.

One obvious possibility is that some budding local young naturalist is doing a spot of spawn “re-location”; having been just such an annoying little nuisance myself as a child where my beloved amphibians were concerned, I know you should never underestimate the determination of frog-loving youngsters! However, the activities of such well-intentioned, if deeply irritating, invaders normally take place during daylight hours – and can usually be curtailed by good fences and a few strategically-planted spiky bushes.

Ducks would probably be the second suspect for spawn theft; mallards in particular seem to be quite partial to frogspawn and they usually turn up at night – or at least around dusk. If the water surface seems a bit oily (from their feathers) and the pond edges muddier than normal, you’ve probably found the guilty parties.

However, none of this really explains why the spawn should hang about for a week and then disappear; it all seems a little too regular for small children or hungry ducks! If the jelly changes in appearance at all during the week it lies there – especially if it goes milky or starts to lose its structure - it sounds as if the eggs themselves are not viable, which would suggest that something else could be going on.

I wonder if you have checked your pond water quality recently. Factors such as a shift in pH, changes in nitrates and so on might be causing problems for the spawn. If you do have water quality records going back to any of the years before this started happening, it might give a clue – and if you haven’t been testing previously, now’s a good time to start.

The only other possibility which springs to mind is that the local frog population isn’t quite as healthy as it was fifteen years ago. Many amphibians are in decline – principally due to the effect of the highly infectious chytrid fungus; an ill or ageing population of frogs might simply not be producing as good quality eggs as before. Your local Wildlife Trust should be able to tell you about the general status of frogs in your area.

What to do About It

One thing you might like to try in the spring is to take some of the spawn as soon as you notice it and leave it somewhere safe – perhaps a garage or shed – in a bucket of pond water and keep a careful eye on it. Nothing’s likely to get at it, so if your problem really is of a feathered or short-trousered kind, you should get a horde of wriggling tadpoles in the normal run of things. On the other hand, if the spawn simply starts to disintegrate, you’ll be able to watch what’s happening, which might give a better clue as to the cause.

The only other suggestion that might be worth trying is to suspend a suitable mesh cover over the pond itself, to prevent anything getting at your spawn; it won’t tell you what has been treating your garden as a snack bar, but it might make it a little less appealing in the future.

Good luck, come February.

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For the third year running my frogspawn has also disappeared. The jelly just seems to dissolve and the whole lot then sinks into the water. I too thought it could be predators eating it but this year I removed some and kept it safe but the same thing happened to that too. I can only conclude that it isn't being fertilised, or not healthily, despite the presence of many male frogs.I am purchasing an air filter shortly so hoping it will improve the water quality. That may help next year I suppose. Really don't know what else to do. Any suggestions guys?
Budgie - 16-Apr-17 @ 11:51 PM
Our frog spawn also disappeared. We have had a few visits from a heron - do they eat Frog spawn ?Whats a good way to test the water ?
willour - 11-Apr-17 @ 11:18 AM
I built my wildlife pond 15 years ago and it has now developed a large population of frogs. A mass of croaking and mating activity in late winter sees large amounts of spawn attached to the marginal vegetation. We also have a small group (four to five) of mallard ducks that visit most days. Its quite puzzling but they don't seem to touch the frog spawn for about two weeks even though they still visit. After this period they then eat the spawn and within a day or two its virtually all gone. It might be that it becomes more palatable to them after a couple of weeks.
ninmit - 23-Mar-16 @ 3:56 PM
I've had the same problem the past 2years and it seems to be happening again. Loads of frogs and masses of spawn which appears healthy then just disappears. I've taken some out this year and so far it seems fine. The small pond has lots of other life and appears clear until the mating frogs churn it up.
Dree - 5-Apr-15 @ 7:52 PM
I have lived in my house for nearly 3years and the pond has produced frogspawn for the last 3 years. There are no fish in the pond. This year (march time ISH) we had frog spawn as usual. We did get frost after it came but its apparently frost proof stuff. I have noticed some big frogs dead with bloated and split stomachs after the spawn arrived, which I removed. Then one day I noticed ALL the frog spawn gone !! Even the duck weed has failed to grow and cover the surface. Someone mentioned the PH and if its any different now than previous years? As the duck week hasn't grown i can only assume the PH is different and not sure higher or lower though. I did notice thousands of tiny bug things in the pond that are still there but mabe not quite the quantity I first saw. VERY STRANGE INDEED.
Reg E Mentle - 2-May-13 @ 8:40 PM
I too have had the same problem with the spawn in my small pond, I've had healthy generations of frogs for years ... that is up to the past two years!, it looked healthy but then turned "frothy" looking and seemed to dissolve. I can't help but notice the two year coincidence we all seem to have and I'm wondering what's going on.
mystic mum - 20-Apr-13 @ 5:01 PM
I have had frog spawn in a small pond in the back garden for years, It always resulted in tons of tadpoles and many frogs. Last year however the spawn appeared and the whole pool was frothy. One day I went to give the grass the first cut of the season and there were hundreds of tiny frogs outside the pool in the grass so i stopped mowing. I was delighted and thought the pond was going to have loads of frogs. We hardly saw a frog that summer. My question is was that froth a bad sign, why were the froglets out of the pond, what would have happened to them. The spawn has now appeared again and I hope that this wont happen. I have a small water fountain in the pool would this be a problem. Look forward to your answer. Mary Lyons
Mary Galway - 21-Feb-13 @ 2:37 PM
Like others, our frog spawn has completely disaapeared for the last 2 years. After last years experience, we covered the pond with netting so no predators from out of the pond could get at the frog spawn. We has 15-20 large 'lumps' of spawn but again it has completely gone. We have carefully checked the pool and there are no tadpoles. The pond is 10'x4' and up to 3' deep. We have no fish but do have some newts but do not think they could have eaten so much so quickly. Before the last 2 years, the pond would have hundreds of tadpoles in from which we would see quite a few froglets.... but none for 2 years
Baldie - 11-Apr-12 @ 9:25 PM
Our frog spawn has also disappeared and done so for the past couple of years. Previously we had loads of tadpoles and froglets. We have a very small pond no more than 4'x6'. The frogs arrive -within 48hours the whole pond is alive with frogs. Heaps of spawn. The frogs depart and between Thursday 15th March and Sat 17th March 2012 the whole lot disappeared. Fortunately because this has happened last year we removed some, which are now thriving in a washing up bowl.( Tadpoles just hatched). We did notice that the water in the pond had changed from clear to muddy looking. We suspected last year that it might be birds so we netted the pond. Still all thespawn disappeared. Bit of a mystery!
Jackie - 21-Mar-12 @ 11:50 AM
Frog spawn sinks.That's why frogs lay it amongst weed.If something causes it to move (like a frog) it may sink.If it's suddenly disappeared I bet its on the bottom.If left there it will die as spawn needs oxygen and sunlight to develope.
iancannes - 6-Mar-12 @ 9:40 AM
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