Nature on our doorsteps: ‘Peter Pan’ tadpoles?

Rosaleen Dwyer is the County Heritage Officer at South Dublin County Council – every week she gives us an insight into nature on our doorsteps and the beautiful biodiversity of its plants and wildlife.

CLUMPS of frog spawn are beginning to appear like magic in ponds or around the edges of lakes, and even in deep roadside puddles where rainwater has gathered.

Once they hatch from their jelly-like eggs in February or March, tadpoles spend between four to six weeks growing as a tadpole.

By July and August, most of them have developed further by growing their legs and losing their tails before finally leaving the pond.

It generally takes three to four months from the egg stage to the fully developed little adult frog.

Sometimes, however, things appear to stand still for some tadpoles, and by winter they are still wriggling little tadpoles with tails and without legs.

These will overwinter as tadpoles.

Roadside puddles that dry up are risky locations for frog spawn

They will hope to survive the cold winter weather in the bottom of the pond, waiting until springtime before they begin to develop once again and finally turn into adult frogs.

Studies suggest a number of possible causes behind this ‘Peter Pan’ option, where they stay in their young stage for longer than usual.

Water temperature may be one reason.

Tadpoles grow quickly in warm water.  Higher temperatures, however, reduce oxygen levels to a point which can slow down or stop their growth altogether.

On the other hand, very low temperatures will slow down a tadpole’s metabolism, affecting its growth rate or stopping it completely.

Overwintering as a tadpole can be an advantage however, if it can manage to survive until springtime.

When the tadpole eventually turns into an adult frog the following spring, there will be no other young frogs around.  This leaves more food for them to grow and mature before the next season’s tadpoles emerge as frogs in late summer.

Interestingly, studies also indicate that tadpoles can in fact speed up their development.  If it looks like their pond is drying up, they can develop very quickly and escape before the pond disappears.