Otters are being killed on Dorset's roads after recent rainfall has left some unable to swim under bridges in rivers, a wildlife charity said.

Dorset Wildlife Trust (DWT) has been made aware of a rising number of otter deaths in the county this autumn.

Most deaths have occurred on the road, a spokesman for the trust said, and are thought to be as a result of otters seeing the roads as an easier alternative to swimming in flood-swollen rivers.

Small ditches and streams are also holding more water, enabling otters to move through the landscape more easily and bringing them into increased contact with the county's highways.

Otters are protected in the UK under the Wildlife and Countryside Act, 1981.

The animals mainly feed on fish and are well suited to life on the water as they have webbed feet, dense fur to keep them warm, and can close their ears and nose when underwater.

In Dorset, otters are regularly seen on the river Stour, however they are mostly shy nocturnal animals and their presence is normally detected by their distinctive smelling faeces (known as spraints) which are deposited in prominent places.

DWT living landscape manager, Amanda Broom, said: "After almost disappearing from England in the 1970s otters have made a gradual recovery.

"In Dorset we are fortunate to have a wonderful network of rivers which support this beautiful enigmatic creature. Dorset Wild Rivers, a Wessex Water funded partnership project, enables us to work with farmers, landowners and fishing clubs to look after and further improve the health of rivers so that they can continue to support otters and other wildlife."

DWT is working with Dorset Police to help ensure safety for road users when an otter is found. Police advise drivers not to stop on dangerous bends in the dark and to consider their own safety and that of others if they find an otter in the road.

If an injured otter is found, police should be contacted if there is a hazard to drivers. If there is no hazard, motorists should call the Environment Agency on 03708 506506, which will advise on what to do with the carcass. If fresh, some carcasses may be sent to Cardiff University for post-mortem examination which can provide a valuable insight into health and biology.

If medical assistance is needed for an injured otter, phone the RSPCA National Emergency number on 0300 1234 9999.

Evidence of snares or home-made snares such as cable ties, an appearance of being shot, trapped or poisoned should be reported to police on 101.