Abstract:

To study the impact of predation on hibernation bats by wintering long-eared owls，bat components in owl food pellets were analyzed at two places of inner city and out city in Beijing from 2003 to 2005.The food pellets were collected monthly each winter and the bat species and numbers in pellets were identified by checking the skulls and limb bones directly.The results showed that four bat species, Eptesicus serotinus,Nyctalus noctula,Pipistrellus abramus and Vespertilio superans were found as prey of wintering long-eared owls and Pipistrellus abramus was the major prey.The species structures of the preyed bat in numbers were different between inner city and out city owls populations.During wintering periods of the three years，the predation rate on Pipistrellus abramus was the highest, the predation rates on Eptesicus serotinus and Nyctalus noctula were much lower，and Vespertilio superans occurred accidentally both at inner city and out city.The annul bat compositions at two places and in the three wintering periods at the out city were different while there was no difference in bat compositions at the inner city.Furthermore，the predation rates on Pipistrellus abramus in 2005/2006 at both inner city and out city decreased obviously.The results revealed that bats availability at the inner city was less stable than that of at the out city.The heavy predation on bats by the wintering long-eared owls would affect the bat population survival negatively in Beijing，and protective measures for bats should be taken to lessen the owl predation load.

Key words: bat, long-eared owl, wintering period, predation pressure