Social and population structure of a gleaning bat, Plecotus auritus

Brown long-eared bats Plecotus auritus occupying 30 summer roosts in north- east Scotland were studied over 15 years. During this time 1365 bats were r inged, and a further 720 recaptures were made. Individual bats showed a hig h degree of roost fidelity, returning to one main roost site; < 1% of recap tured bats had moved among roost sites, and all recorded movements (n = 5) were < 300 m. Adults of both sexes were loyal to the roost sites at which t hey were first captured, indicating long-term use of roosts. At least some juveniles (n = 32) of both sexes returned to the natal roost. Mark-recaptur e estimates indicated that colonies of this species were substantially larg er (c. 30-50 individuals) than assumed in previous studies. Plecotus auritu s differs from most other temperate zone, vespertilionid species in that th ere was no evidence of sexual segregation during summer, with males present in all colonies throughout the period of occupancy. Population structure i n summer seems to be consistent with a metapopulation model, with discrete sub-populations showing minimal interchange. The group size, colony composi tion and population structure described in this species may be associated w ith the wing shape (particularly aspect ratio) and foraging behaviour of P. auritus. It is postulated that relative motility, linked to wing structure , may affect the distribution of individuals, and may have implications for the genetic structure of this species. Correlations between aspect ratio a nd both colony size and migratory behaviour, across British bat species, in dicate that wing shape could be an important factor contributing to pattern s of social behaviour and genetic structuring in bats.