A RARE species of British bat, not seen in Hertfordshire for four years, has been found hanging around in Watford.

A pair of Serotine bats, one of the country's largest bat species, were discovered at The Grove estate, off Hempstead Road.

They were found by Mr Dave Cove of the Hertfordshire and Middlesex Bat Group, which has been brought in to advise on the care of wildlife during the 300-acre estate's transformation into a luxury hotel complex.

The nocturnal couple were sheltering in one of ten specially designed bat boxes, placed in trees to protect other bat species such as the less rare Pipistrelle bat, which inhabit the grounds.

Mr Cove said: "This is a great find, as the Serotine bat is quite a rare species. Bats are in serious decline in the UK and, during the past 20 years, the bat population has fallen by some 70 per cent, due to the increasing use of chemicals used in timber treatment and the destruction of habitats."

Serotine bats have dark brown fur, a pale underbelly and black faces and ears and can grow up to 80mm in length.

They sometimes flop on to foliage to catch large insects and, having caught a big beetle, will cruise around slowly, chewing and dropping the bits it doesn't fancy eating.

The bats are currently hibernating but it is hoped they will breed in the spring.

Other interesting species spotted at the Grove include the Daubenton or Water Bat and Natterer bats.

The Daubenton, thought to have been attracted by the restoration of two ornamental lakes, like to skim close to water and scoop up insects from the surface, using their feet and tail.

Natterers, which have pink limbs, like lodging themselves in small crevices and can be found in unusual positions, including resting on their heads.

A special hibernation area, or hibernaculum, has been created at The Grove to provide a safe resting place for the creatures.