Roosts, echolocation calls and wing morphology of two phonic types of Pipistrellus pipistrellus

Variation in the number of bats in maternity roosts of two phonic types of P. pipistrellus was investigated. Also, bats of the two phonic types were c aught at maternity roosts, and their wing morphology and echolocation calls studied, 45 kHz P. pipistrellus maternity roosts contained significantly f ewer bats than 55 kHz Fl pipistrellus roosts. There was significant variati on in mean frequency of maximum energy (FMAXE) of echolocation calls used b y bats among roosts of 55 kHz P. pipistrellus. but not among roosts of 45 k Hz P. pipistrellus. However, within each phonic type differences among roos ts only accounted for a small proportion of the variation in echolocation c all frequency; a much larger proportion was due to differences among indivi duals. Forearm length, an indicator of body size, was larger in 45 kHz P, p ipistrellus than in 55 kHz P. pipistrellus, but there was no relationship b etween body size and geographic roost location in either phonic type. Varia tion in echolocation call frequency was not correlated with body size in ei ther phonic type. Variation in echolocation call frequency among individual s may allow roost members to identify others in their group. but it is more likely to have evolved as a result of other influencing factors. Some vari ables of wing morphology differed between the two phonic types, but it is n ot clear how these differences relate to flight performance.