Tall herbage by the river is a good habitat for beetles and water snails. These include the tiny Desmoulins Whorl-snail, a Europe-wide rarity which won its moment of fame when a colony held up the construction of the Newbury bypass.
Above: American Signal Crayfish
Crayfish are very common in parts of the river, lurking by day in holes and roots on the bank, but emerging at dusk to feed. Most if not all are now the American Signal Crayfish, an escapee from crayfish farms, which has replaced the native White-clawed Crayfish in most southern rivers, although a small population still survives in the River Lambourn.