Otters - Talk by Chris Matcham

CHRIS MATCHAM gave our first lecture of the winter season on 8th September. Chris has worked in otter conservation since 1993 and gained his initial experience on the upper reaches of the River Itchen in Hampshire. In 1998 he joined the Surrey Wildlife Trust as Otters and Rivers Project Officer. He is responsible for surveying all of Surrey's rivers, analysing the problems and advising landowners on methods of improvement and conservation as viable habitats for all wildlife as well as otters.

Chris brought with him a beautiful stuffed otter, a two-year-old male that had died in a road accident. It weighed about 25 lb with beautiful soft fur. A female is much smaller, weighing about 15 lb. Otters were plentiful in every county of the British Isles until 1950 and then declined rapidly until 1970, when they had become restricted to Scotland and Ireland with only small pockets in Wales and East Anglia. The cause was loss of habitat through changed agricultural practices, pollution of the water by excessive nitrates, but more specifically from DDT. The nitrates and DDT not only disrupted the food chain but also affected their reproductive success. DDT is cumulative in tissues, and top predators such as the otter get the lot. It also gets in to the milk of lactating females to the detriment of the cubs. In 1979 the otter was declared a protected species, DDT was banned, steps were taken to clean up the rivers and wildlife officers were appointed. The otter is now making a slow comeback.

Chris then described the ideal habitat for otters illustrated by examples from the River Itchen: clear water, a gravel bed for spawning fish, a well-balanced ecosystem of vegetation, aquatic insects and fish, and good cover along the banks where they can leave the water and remain concealed.

Chris works closely with the landowners who are generally cooperative about conserving the wildlife. Some of the methods adopted include restricting the access of cattle to only a few places on the riverbanks to cut down the erosion, which silts up the gravel beds essential to fish spawning. They are also asked to leave a margin of vegetation along the banks to provide cover and to act as a filter to reduce fertilizer run-off. Often the flow of water is very strong under a bridge and the otter will take an easier way by crossing the road. To discourage this, fences are built on either side of the bridge and, where possible, pipes and walkways have also been constructed. They have also constructed some artificial holts from wood and, in some cases, brick with pipes leading to the riverbank. They are then covered with brushwood and long grass which also encourages a variety of other wildlife.

Unlike the mink, otters are shy nocturnal creatures seldom seen. They also almost exclusively eat fish, whereas mink kill everything on a river including mammals and birds. Otters and mink coexist and rarely fight. The exception is when a female has cubs to defend, which a mink would take if it could. The mink is half the size and much lighter and is no match for the otter, being invariably killed or driven off.

Otters are extremely difficult to monitor and their spraint and paw marks are often the only indicators of their presence in an area. The spraint marks the territory and is usually dropped in the same place, which is of great help to the researcher. It has proved possible, but expensive, to check the DNA from fresh spraint and this was used in a study on the River Itchen. It was discovered that the river could support only eight otters. Most were females each with an eight-mile territory, but the dog otter ranged the whole territory and travelled up to 25 miles. They have a series of resting places along their territory under tree roots or logs or in deep cover. Only the females use holts for their cubs. These are a little way back from the river. When the cubs eventually emerge they are reluctant to take to the water and the mother has to teach them to swim.

Surprisingly, on rivers, the otter does not cause fishermen much of a problem as it feeds almost exclusively on fish less than six inches long and under a year old. These are often in shallow pools, are abundant and so plenty survive to grow larger. Furthermore, their favourite food is Bullheads. Lake fisheries can however be a problem as the temptation is great and the fish are stocked and are more restricted than in rivers. One solution is to fence the ponds.

The otter is making a comeback. It has spread to the West Country and to Hampshire and there is evidence, and occasional sightings, on the borders of Surrey. One such otter was seen on a railway line where it had unfortunately been electrocuted and could not be recovered. There is plenty of suitable habitat in Surrey, such as the headwaters of the River Wey, with clear, well-vegetated pools and banks. It may take 25 years, but if the progress currently being made continues, otters will be back in our streams and lakes.

CHRIS BRADING