By Alex Kirby BBC News Online environment correspondent

Out of its parish: An unexpected visitor

A solitary specimen of the grey long-eared bat turned up at Dunster castle, Somerset.

But droppings found there suggest the new discovery has some companions sharing its roost.

The find was made by Phil Richardson, bat conservation officer of the National Trust, which cares for the castle.

The bat, found occasionally 150 miles away in the extreme south of England, was roosting in one of the roof voids of the castle's old stables, now used as the trust's shop.

Mr Richardson said: "Finding such a jewel on a routine visit was a real treat. We now need to find the main summer roosting site and ensure that full conservation measures are in place to help this amazing species.

Improving diet

"All bats and their roosts are protected by law, but we like to do more than just protect the species that live in our properties - we like to improve their lives.

"Apart from this amazing bat we have also discovered the roost of endangered lesser horseshoe bats and serotines, another species suffering declines in population."

The trust is looking at the management of the grounds and farmland around the castle to see what can be done to increase the insect diversity for bats.

It is to conduct a detailed survey of the site to see how many rare creatures are living under the eaves.

Grey long-eared bats are closely related to the commoner brown long-eared species, but have differently-shaped ears and a shorter thumb.

Sarah Leggatt of the Bat Conservation Trust told BBC News Online: "We're always excited when a new bat roost is found, especially when it's a rare species.

"The more roosts we know about, the better the idea we can get of how bat populations are doing in the UK."