Tadpoles have not developed into froglets and it’s autumn, is something wrong?
No, it’s quite common for tadpoles to overwinter in the pond if they have not experienced the right conditions to develop.
Tadpoles/larvae usually develop into young amphibians and leave the pond during the summer months, but occasionally you might still see them in the pond throughout autumn and winter. These ‘overwintering’ tadpoles complete their development the following spring (if they survive the winter weather).
There could be several reasons for this slow development. The pond may be so crowded that the tadpoles are short of food – this is likely to resolve itself over time – or the pond may be too cold, due to a shaded location or steep-sided construction. If the pond is shaded, consider cutting back some of the overhanging vegetation to increase the amount of light and warmth reaching the surface of the water.
At this stage, do not attempt to help these slow-growers by providing extra food or taking them out of the pond – you could end up with them completing their development in the middle of winter when there are few natural sources of food in the garden to support them. They should be fine in the pond until next spring.
There is evidence to suggest that this may be a deliberate strategy for some frogs, as tadpoles that overwinter in the pond and leave the water in the spring have an advantage over those tadpoles that complete their develop in one year and leave in late summer.
Sometimes frog and toad tadpoles have a genetic abnormality which means that they will remain as tadpoles for their whole lives. If a tadpole lacks the gene which produces the growth hormone thyroxine they will be unable to metamorphose into froglets or toadlets. This is nothing to worry about since it is a natural mutation and only occurs in a very small number of tadpoles. The tadpoles will continue to feed and grow within the pond all year and may survive as tadpoles for several years.
Tadpoles are behaving strangely (e.g. swimming in circles), what’s going on?
It can be difficult to explain amphibian behaviour; if they’re not dying it’s unlikely to be anything to worry about.
Occasionally you may see tadpoles behaving in an unexpected way – they might be lying listlessly in the water or swimming in circles. It can be difficult to explain unusual behaviour but it’s rarely anything to worry about. Behaviour is often linked to temperature – the warmer it is the more active they become.
Spawn has been laid in an unsuitable place, should it be moved to pond?
If you know of a nearby garden pond it’s ok to move spawn in these situations.
Frogs may return to places where ponds used to be and, in desperation, spawn on the ground or in an unsuitable place. Often, frogs choose to lay spawn in small water bodies including puddles and garden tubs. This strategy can be beneficial for frogs – such ‘ponds’ often lack predators meaning the chances of tadpole survival could be higher. But it’s only successful if the tadpoles can develop and leave the ‘pond’ before it dries up so often the strategy fails and tadpoles are left without enough water to survive. To a degree this is a natural phenomenon, typical of amphibians around the world. However, you may want to ‘rescue’ such tadpole populations, either by regularly visiting the pond and topping it up (which may not be feasible) or by moving the spawn/tadpoles to another pond.
If you choose to do this we advise introducing tadpoles to a pond as near as possible, ideally to a garden pond within one mile. Moving tadpoles or spawn around is not normally recommended as you can accidentally transfer wildlife diseases or invasive plants, so for this reason we do not recommend that you release tadpoles into the wild or in public water bodies (such as rivers, canals, parks or streams). In these cases it’s ok to relocate the spawn/tadpoles as temporary ponds are less likely to contain these things.
You may decide to raise these tadpoles in a tank at home or school, or think about creating a pond yourself. The froglets that the tadpoles develop into should be released into a suitable habitat near to where they were found. The only worry with this is that it encourages these froglets to return to the area (where there is no pond) to breed themselves in the future, perpetuating the problem.