Sex discrimination and roostmate recognition by olfactory cues in the African bats, Mops condylurus and Chaerephon pumilus (Chiroptera: Molossidae)

The ability of two species of African insectivorous bats (Angola free-tailed Mops condylurus and little free-tailed Chaerephon pumilus) to distinguish between males and females and roostmates from strangers in scent-choice experiments was tested. Both sexes of M. condylurus and male C. pumilus discriminated between sexes based on odours collected from the interaural and muzzle glandular areas, whereas female C. pumilus did not show any preference in either trials. Female M. condylurus from intermediate sized colonies (c, 200-600 individuals) distinguished female roostmates from strangers. There is some indication that roostmate recognition may vary inversely with the colony size of the test-subject suggesting that recognition is individually based, but further studies are necessary to determine if this is so. Histological work revealed that the interaural and muzzle area contain sebaceous glands and that the quantity of the glandular tissue is sexually dimorphic in both species for the interaural area, with males having more tissue, but not for the muzzle area. The presence of osmetrichia using SEM was also observed in the interaural area of both sexes of M. condylurus and in male C. pumilus. Their presence and association with sebaceous glands, as well as the results of the scent-choice experiments are indirect evidences of use of chemical signals, possibly pheromones, by these bats.