Otters

Thomson Ecology has extensive experience of otter surveys. Our mammal specialists hold the relevant licences.

Ecology and conservation status

The otter (Lutra lutra) is one of the larger British mustelids. Males can be up to 1.2m long from nose to tail and weigh up to 10kg. The females are smaller. The otter is largely nocturnal and elusive, so seldom seen.
Otters can be found in all types of wetland including rivers, streams, lakes, marshes and ditches as well as coastal areas. An otter’s home range is large (up to 40km) and can encompass a variety of habitats with a number of refuges. They live in holts, generally holes under tree roots near the bank and cavities under bridges. Breeding can take place at any time of year, and 1-4 cubs can be raised, who stay with the mother for about a year before leaving to establish new territories. The diet of the otter is predominantly fish, with eels being a particular favourite.
Otter numbers declined during the 1960s and 1970s, and they became extinct in much of the UK. Pollution was the most likely cause of this decline and in recent years, as the river water quality has improved, otter numbers have begun to recover

Protection and legislation

Otters and their habitats are fully protected under both UK and European legislation. There are designated areas of protection, but even outside of these sites, otters and their holts are fully protected.
The otter is a Priority Species under the UK Biodiversity Action Plan and has also been adopted as a Species of Principal Importance in England under Section 41 of the NERC Act 2006 (Section 42 in Wales) and the Conservation(Scotland) Act in Scotland. It is government policy that local authorities protect such species from the adverse effects of development.

Licences and surveys

A licence will be required whenever disturbance to otters or damage to their holts is likely to occur.
Otters are highly mobile and wide ranging. A typical otter survey involves not only the watercourse immediately affected by the development but also an additional 2km upstream and downstream. A qualified ecologist will record the habitat features and search for signs of otters.

Mitigation

If otters are present on site it could be a reason for refusing planning permission unless you can clearly demonstrate that they will be protected during the development process and that disturbance will be kept to a minimum.
A few modifications to site practice and layout may be sufficient mitigation. Examples are locating site compounds away from otter habitat, avoiding floodlights at night and excluding construction workers from these areas. Particular care must be taken to avoid encouraging otters on to roads as traffic mortality is a significant threat to otter populations.
If destruction of an otter holt is unavoidable it must be done when otters are not present and the area around the holt suitably fenced to avoid return.
The overall objective is that otter habitat should be maintained or failing that, compensated for any losses.