Rivers can run for many hundreds of miles. The longest river in the world is the Nile in Africa. It is 6,700km long. The longest river in Britain is the River Severn, which is 354km long.

Mammals

OtterThe otter was one of our rarest mammals. It declined rapidly from the 1950s to the 1970s because of dangerous pesticides and loss of riverside trees. But since then efforts to clean up our rivers has meant that the otter has now returned to every county in England!

Living in an undisturbed stretch of river, the otter is perfectly adapted to swimming under water.

 The otter is at the top of the food chains, eating mainly fish. It makes its home (holt) underneath overhanging tree roots.

A muddy bank provides an ideal place for the water vole's burrow; it is active by day, feeding on the roots and shoots of grasses, reeds, willow and other waterside plants. Once common throughout lowland Britain, this attractive vole is now declining because of habitat loss and pollution. Despite this the IUCN has classified it as Least Concern.

The water shrew and the mink are more mammals which you may find living in this habitat.

Read More: Life at the Bottom

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