Roost utilisation by female Leisler's bats at an Irish nursery roost

• Main Author: Forsyth, John
• Published: University of Aberdeen 2011
• Subjects: 569.4; Bats : Bats Behavior
• Online Access: http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.553772

Study of a Leisler's bat maternity roost in Co. Tyrone, Northern Ireland, 1997- 2000 used the marking of individual female bats with PIT (Passive Identification Transponder) tags with infrared filming of bat movements at the roost entrance. This provided data for analysis of bat activity through the maternity season, without interference to the bats. PIT -marked bats were analysed into four activity categories. Evening exits and morning entrances to the roost showed an abrupt change in pattern at 8th June 1999. Flight patterns before and after s" June showed significant changes. Lengths of flight of one- and two-part flights per night were not significantly different. Principle component analysis showed a significant relationship of emergence time to solar radiation at 21 OOh GMT. Patterns of activity in the tunnel to exit, and following entry, were monitored and analysed. Survival rate estimates, Phi, for 1997 to 2000 varied from 0.61 to 0.77. Significant differences in body measurements between female adult and female juvenile bats were demonstrated. The profound changes in behaviour of the bats to sunset and sunrise respectively were also consistent with a risk avoidance strategy in the heavily pregnant females that may be prone to aerial predation risk. The large changes in roost composition while total numbers of bats using the roost remained almost unchanged highlights the problems of attempting to resolve roost phenology by visual roost counting such as the maximal visual roost count on any one night. Analysis of the sequence of emergence and individual consistency in timing of emergence in pregnancy and lactation strongly suggested that this sample of bats did not co-ordinate their behaviour in any way.