Mammals

Mammals

Otter

The Eurasian or European otter is a native to Britain and is one of its largest carnivores. A full-grown male otter averages 1.2m in length and weighs about 10.5kg. Females are smaller, weighing in at about 7kg and reaching little more than 1m in length.

The otter is beautifully adapted to its semi-aquatic life style. It has a long streamlined body powered by a thick rudder-like tail and webbed feet on short powerful legs. The coat is waterproof and consists of 2 layers, a thick under layer of insulating downy fur and an outer layer of longer guard hairs that trap air to form an insulation layer between them.

Every river catchment in Northumberland boasts signs of otter. In more recent years they have even started to populate urban centres such as Blyth, Morpeth and Newcastle-upon-Tyne. In many cases however, this expansion is into largely ‘unsuitable’ areas, which support impoverished prey resources and poor habitat qualities. Changes in the use of pesticides, improvements in water quality and habitat have been largely responsible for the return of the otter to Northumberland’s rivers.  It has also led to the sharp increase in the number of fatalities on the region’s roads as the population expands to seek new territory.

Much of the life of an otter is actually spent out of the water sleeping; with hunting bouts rarely lasting longer than half an hour. They are active at any time of day but are usually nocturnal when it is easier to catch prey.

Water Vole

The water vole is the largest of the British voles weighing between 200 and 350 grams, with male voles normally being slightly larger than females. As a result of their size they are commonly mistaken for the brown rat.

Distinguishing features are:

  • Rounded body
  • Blunt muzzle
  • Long furry tail
  • Almost invisible ears
  • Darker colour
  • Buoyancy (body is visible above surface of water)

Water voles favour a slow-flowing water course with thick herbaceous riparian vegetation, where extreme fluctuations in water levels are rare. The upper reaches of rivers, small backwaters, ditches and ponds are strongholds for the species. They avoid excessively shaded watercourses with extensive shrub and tree cover.

The water vole was formerly a common sight to anglers and passers-by on many inland waterways across the country. Populations have declined by almost 70% nationally since the 1960s. The principal reasons for the decline in the water vole populations are inappropriate wetland management and the introduction of the North American Mink which, as a semi-aquatic mammal, is able to follow its prey over land, under water and into burrows.