Otters are one of the most popular animals with the public and are increasingly found all over the UK. There was a dramatic drop in numbers between the 1950s and 1970s, which most scientists think was caused by particular pesticides called organochlorines that built up in their food. As these were banned the otter population started to recover, helped in the early years by conservation projects reintroducing them to areas where they had gone locally extinct.
Today otters are most common in Scotland, Wales and southwest England but are also found across other parts of England as well.
Otters live along rivers often covering a wide area – male otter may range over up to 20 miles of river. They can also travel overland between rivers and females often choose areas away from rivers to give birth so that the young cubs are not disturbed by other otters.
Otters are protected under European law (The Conservation Regulations) making it illegal to kill, injure or disturb them or to damage or destroy one of their resting sites known as a holt. As with most protected species it is possible to obtain a licence to move otters out of the way but it is usually better to protect the river bank both for otters and other wildlife, providing a natural corridor through a site.
Because they can move over such a wide area otters often need to cross roads and there are detailed guidelines on how to design road bridges to reduce the risk of them being killed. On smaller streams this may involve a separate otter tunnel that is on higher ground than the main culvert, while on larger rivers bridges need to have their supporting walls set back to leave part of the bank. Despite being excellent swimmers otters don’t like swimming under barriers and are more likely to leave the river and cross the road if there is no dry way underneath.