KILLER mink are being blamed for almost halving the number of water voles living along the banks of Suffolk's rivers.Today wildlife experts launched a survey to find out if trapping the mink over the past few months has been effective in stopping the decline – or whether the voles are still suffering from other environmental problems.

KILLER mink are being blamed for almost halving the number of water voles living along the banks of Suffolk's rivers.

Today wildlife experts launched a survey to find out if trapping the mink over the past few months has been effective in stopping the decline – or whether the voles are still suffering from other environmental problems.

Suffolk Wildlife Trust's Water for Wildlife project hopes the three-month study this summer – and similar surveys in the years ahead – will provide new evidence in its campaign to help the threatened animals.

Mink trapping was introduced last winter and the SWT has been working on the Deben at Easton with gamekeeper David Denny, who sets the traps.

The survey, funded by the Environment Agency, will look at the 73 sites visited during the 1997 county water vole survey on the Deben and, later on, the Alde river catchments.

"One visit to each site will be sufficient to collect data on water vole presence, abundance and some basic information on habitat quality and management. The latter of which is useful in developing future strategy," said SWT Water for Wildlife advisor Penny Hemphill.

"By concentrating on two of the river catchments where mink are being trapped we will be able to re-establish baseline data on water vole populations.

"These sites should then be re-surveyed annually to prove or disprove the effectiveness of mink control."

The decline of water vole populations is causing widespread and increasing concern nationally.

The 1997 survey showed that in East Anglia the number of water voles had halved since 1989. In other counties the declines are even more dramatic –representing one of the most serious declines of any British wild mammal.

Apart from predation by mink, other threats facing water vole include loss and fragmentation of habitat, incidental poisoning by herbicides and rodenticides and disturbance and habitat damage caused by increased use of waterways.

FACTFILE: water voles

n The water vole is a rodent almost entirely associated with wetlands and is found living in the banks of ditches and rivers.

n It is our largest vole and an expert swimmer, using the water to escape predators.

n It feeds on all kinds of waterside plants leaving characteristic bitten-off lengths of stem and oval droppings.

n Although once found throughout the UK, the water vole has declined dramatically in the last 10 years from an estimated 2.3 million in 1990 to 354,000 in 1998.

n Known as a "water rat", it has a blunt muzzle, small hairy ears and a rounded body, and a relatively long but hairy tail.

n Adult voles are between 14cm and 22 cm in body length and weigh around 300g.