The Underwater Jungle

Pond Skater

Pond Skater

The calm surface of the pond in my garden hides all manner of creatures, and once in a while, I like to take a look to see how everyone is getting on, and who has turned up. There is nowhere in the garden that illustrates so easily the different levels of the ‘web of life’, and a short spell of pond dipping often turns up all kinds of creatures.

Starting at the top, I found some pond skaters. What voracious predators they are – they can detect the slightest tremor in the surface of the water through their legs, and can move at extraordinary speed when some poor unfortunate insect ditches into the pond. Often, half a dozen will head towards the source of the commotion at once, and then all of them will puncture their prey with their long, sharp mouthparts. They are the closest animals in the garden to wolves, and are, to me, just as graceful, although they skate on the surface tension rather than lope through the pine forest.

The common backswimmer is another predatory bug which is said to be able to puncture the skin of an unwary human. Last year I found lots of the pallid, blue-eyed nymphs, which are miniature versions of the adults, but haven’t seen any yet this year.

Water Boatman

Common Backswimmer

This seems to have been a pretty good year for frogs – certainly every netful of water had half a dozen tadpoles in it. I find it interesting that they develop at such different rates – one of the tadpoles above is just starting to develop the buds of the back legs, whilst the other one has fully developed limbs. Whilst most tadpoles complete their life cycles during a single year, it has been observed that some tadpoles actually survive the winter as tadpoles, becoming adults in the following spring.  It’s a risky strategy – an adult frog is much more likely to survive a cold winter than a tadpole – but on the other hand, if the tadpole does survive, it will have the jump (pun intended!)on all the rest of the frogs who are still hibernating when the spring comes.

Once the front legs start to develop, the tadpoles turn from a vegetarian to a carnivorous diet, and are so able to turn the tables on some of the smaller creatures that may have been snacking on them earlier in their lives. Dragonfly and beetle larvae will eat small tadpoles, and even the backswimmers and pond skaters are not averse to preying on injured individuals, so I imagine them heaving a sigh of relief as they metamorphose.

 

Tadpoles

Tadpoles

 

Not everything in the pond is a predator, however:

Water Hoglouse

Water Hoglouse

A while ago, I wrote a piece about woodlice, and here in the pond I find their water-living relatives, the water hoglice. They bumble about in the debris at the bottom of the pond, helping to recycle all the leaves that seem to find their way in however meticulous I am about skimming them off. A handful of dead leaves is home to thousands of the creatures, varying in stature from the size of a grain of rice to the length of a fingernail. They always seem to me to be on a mission from which they are loathe to be distracted, as they bustle through the water. The females, like female woodlice, carry their eggs about with them in a brood pouch under their bodies.

Now, have a look at this little film.

What we have here, somewhat to my surprise, is a leech. Fortunately, this is not the gigantic bloodsucking leech found in the tropics,  but an inoffensive little leech that probably doesn’t suck blood at all, but lives instead by ingesting tiny invertebrates. I didn’t notice it at first, because it  compressed itself into the shape of a seed or twig.

Compressed leech

Compressed leech

But soon it was off, looking for cover rather than prey I suspect (notwithstanding the alarm of the tadpole in the little film)

Extended leech

Extended leech

However, the commonest large (ish) creatures in the pond are definitely the snails.

Tadpoles and snails

Tadpoles and snails

All of the round shapes that you can see here are baby snails. Unless the pond is actually frozen, there are always some adult snails, swimming blithely through the water on their backs or munching away at the algae at the side of the pond. I have Great Pond Snails, Wandering Pond Snails and Dwarf Pond Snails, and the pond seems to suit them very well, if the volume of eggs that the Great Pond Snails lay is anything to go by:

Great Pond Snail Eggs

Great Pond Snail Eggs

These gelatinous caterpillar-shaped objects are actually the egg masses of the Great Pond Snail, and will no doubt contribute further to the molluscan presence in the water, and serve as a source of food for the pond skaters, common backswimmers, young frogs and dragonfly nymphs.

My pond is a source of surprise and delight to me. Who knew that I had leeches? This might not be everybody’s idea of a happy Saturday discovery, but it fills me with joy that so many different kinds of living thing can be found right here in London, in a little back garden. We are surrounded by so many wonders, all we need to do is make a little bit of space of them and they will come.

 

 

 

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