Froglets

We've had to watch our step in the garden during this week's wet weather, because the tadpoles in the pond have been metamorphosing into tiny froglets that are about the size of my thumbnail.  They would be so easy to tread on. Still, it's a great excuse for not mowing the lawn, as they seem to spend a lot of time in the grass.

A tiny froglet like this has a lot of growing to do before it reaches reproductive age. When they are this size they are prey for birds and perhaps even larger ground beetles and centipedes

They need to adapt quickly to their change in buoyancy during the last days before they leave the pond. Tadpoles absorb oxygen dissolved in water via external gills and over their skin surface and if they stop swimming they sink, but once they become froglets their internal lungs take over and the air inside their bodies makes them float to the surface to gulp more air. 

This one seems to be just chilling, floating with only its nostrils above the water. 

At this stage the froglets must be able to climb out of the water but ...
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...... when they first metamorphose they are light enough to sit on the water surface.

There is often one important hazard that froglets face when they try to leave ponds that are surrounded by paving on warm, sunny days. Dry paving stones can become very hot underfoot and I have seen froglets perish in their attempts to cross them, so an area of grass around a pond that reaches down to the water surface offers a much safer escape route.

Pond Life

 A quick sampling of the tadpoles in our garden pond showed that many of them were still some way off developing limbs, which I guess is a sign of the late spring - the frogs spawned very late this year. (Double-click for a larger image).

This tadpole is a sharing the trough that I photographed it in with a flatworm.

A water log-louse Asellus aquaticus. There are vast numbers of these scavengers down at the bottom of the pond, where there's  thick layer of decaying leaves.

Underside of a water hog-louse. These crustaceans are isopods - all their legs are more or less the same length. For more isopods, click here and here.

Possibly the least lovable animal in the pond - a leech. I suspect that these parasitize the pond snails. The dark patterning is its digestive system, visible through the body wall.

Slug slayer

After 12 hours of apocalyptic rain the clouds finally parted and the sun came out - and so did the frogs. Now that they've spawned in the garden pond, which is swarming with tadpoles, our resident frogs spend most of their time lurking in the flower beds and there's nothing they like better than a good rain storm, which brings all the slugs crawling out from the undergrowth. 

Very satisfying for the frogs, and from a gardener's perspective too, when they swallow these slimy pests.



The frogs tend to be very wary when they first emerge from hibernation but as the months go by they become accustomed to me gardening around them and sometimes become quite tame. On several occasions in the past I've managed to entice one to take small slugs presented on the tip of my finger, which makes a change from hand-taming robins with meal worms.

Riotous spring

Any doubts that spring had finally arrived were dispelled yesterday by a honeybee trapped in our greenhouse (and safely liberated) .........

............ celandines coming into bloom all over the garden ...........

........ and frantic frog activity in the garden pond.

Since the frogs first emerged from hibernation the pond has frozen and thawed several times, but the chilly spring doesn't seem to have .....

.... dampened the frogs' ardour.

By this afternoon most of the females had left the pond, looking somewhat slimmer and leaving behind massive quantities of frog spawn.

Too much testosterone....

Do frogs have testosterone? I don't know, but what I do know is that there's amazing pent-up aggression in the frogs in our garden pond. This one surfaced just in front of my pocket camera which is small and waterproof - ideal for pond photography - but it's also silver.

The white throat patch of a frog, which inflates when it calls - also seems to be be part of its visual challenge display to rival males and I suspect that it probably mistook the bright gleam of my camera in the sunlight for a rival frog - so it lunged....

.... and he may well now have a bruised nose. You can see the eardrum quite nicely in this picture, just behind the eye.

Once male frogs find a mate they tend to hang on to them come what may - which makes them much more approachable............

How to talk to frogs

Just 10 days ago our garden pond was covered in a layer of ice. Yesterday I counted 44 frogs in it, wallowing in a sea of gelatinous spawn. They certainly haven't wasted any time in reproducing and they're still at it..... it's a bacchanalian orgy in there. This year I've covered the pond with a net, to ward of the predatory heron that wrought terrible havoc last year in the midst of all this amphibian lust.

.... meanwhile the spawn that has already been laid is beginning to develop. If you look closely at these eggs you can see a furrow across the centre of each. This is the first division of the fertilised egg, the first step on the road to it becoming a tadpole and then ....... if it's incredibly lucky, a frog. You can find a detailed illustrated description of the whole process, from fertilisation to froglet, here.

Yesterday I tried a little experiment that I've tried before... which always works. I used a portable recorder to record the frogs' mating calls, then played them back to them. The effect was instantaneous - 44 pairs of eyes swivelled in my direction and they all advanced towards the recorder. Intimidating.