@Andrew Swales Martens mostly. Without the electric fence they can climb on the cage top and catch birds through the wire during their sleep or frighten them to fly and catch them then. There have been some ugly accidents - although the marten can´t get the bird through the mesh, they can still bite off some wings or legs :-(
@Manumea Thank you! Absent from our part of England, that's not a spp which would be in the front of our minds! The electric fence is new, and not part of the original construction - are Martens a 'new problem' ?
@Andrew Swales Well, martens now live quite often in large cities. But zoo is situated in their natural environment. The fence is new because we now have the ways and will to protect every zoo inhabitants as good as we can.
I believe the martens in question are Beech Martens, so a species which is entirely absent from the UK - and which over on the continent is not much less commonplace in towns and cities than the Red Fox!
On a side-note, these electric fences can give a nasty jolt - when I visited Plzen last week and was crouched next to an aviary taking photographs of a particularly fine pheasant, my elbow knocked against an (until then) unnoticed hotwire........ so they would definitely work very well against a Beech Marten!
