Every pond is an island
A new pond dug in a bare field will fill with life within a couple of years, and none of it walked there. A pond is a patch of water surrounded by land, which to a WATER SNAIL or a small FISH is as impassable as an ocean — so everything living in yours arrived by air, or by accident.
Darwin was fascinated by this and did the obvious experiment: he dangled duck feet in a tank of pond water, pulled them out, and counted the tiny snails clinging on. They survived for hours out of water, quite long enough for a DUCK to carry them to the next pond down the valley. Seeds, eggs and water fleas travel the same way, stuck to feathers and MUD on a bird's legs.
The dragonfly you see has spent years underwater
The DRAGONFLY skimming the surface for a few summer weeks is at the very end of its life. It spent the previous one to five years as a nymph on the bottom of the pond — squat, drab and one of the fiercest predators in fresh water.
Its weapon is a hinged lower lip folded under the head, which shoots out in a fraction of a second to seize a TADPOLE, an INSECT or a small FISH and drag it back. When it is finally ready, the nymph climbs a REED or BULRUSH stem out of the water, splits down the back and the adult hauls itself out to dry. The empty case is often still gripping the stem afterwards, which is the best thing to look for on a pond dip.
One of these can stop a housing estate
The great crested NEWT is protected in Britain to a degree that surprises people. It is an offence to catch one, disturb one, or damage the pond it breeds in, and developers who find them have to apply for a licence and often build the newts a replacement pond before touching the site.
It has made the animal quietly famous on building sites, and given it a reputation as an obstruction, which is a little unfair on a creature about the length of a finger. Surveys are done at night with a torch, because that is when the males are displaying underwater with a wavy crest they grow for the season and lose again afterwards.
Small, disappearing, and easy to replace
Britain lost a great many of its farm ponds across the twentieth century — filled in as fields were merged, or left to silt up once cattle no longer drank from them. That loss is why garden ponds now matter out of all proportion to their size: a washing-up bowl sunk in a lawn will have things living in it by the following summer.
The grid holds what turns up. Around the edge the REED, BULRUSH, LILY pad, PONDWEED and green ALGAE; on the BANK a patient HERON; on the surface a DUCK, a MOORHEN and every RIPPLE; and below, a BEETLE, a SNAIL, a FISH, and the FROG, TOAD, SPAWN and TADPOLE whose full transformation is covered on our life cycles page.