Social interactions and communication in two African bats (Chiroptera: Molossidae)

I picked two common African bats, Mops condylurus and Chaerephon pumilus, which live in multi-sex and multi-age roost, to study the multiple interactions occurring within the roost. Mating was of particular interest as it is a key factor in understanding mammal sociality. To further our knowledge of molossid social organisation and communication, I placed individuals of both species in captivity and recorded their behaviours using surveillance cameras for more than a year each. Observations clearly revealed that although the two species are close relatives with behavioural similarities, they differed drastically in their mating strategies. Female of both species formed strong associations and both sexes used agonistic bouts (mainly over roosting position) to establish dominance hierarchies. While male M. condylurus set up, scent-marked, and defended territories, C. pumilus males scent-marked areas but did not defend them. The mating system of M. condylurus was mainly based on resource-defence polygyny with occasional female-defence whereas two C. pumilus males (of unknown relatedness) shared both the roost and the females, making their polygynous system more ambiguous. Data on gestation and lactation were also recorded.;As sociality cannot occur without communication, I looked at olfactory displays and social vocalisations. Bats used a range of social calls and both sexes of M. condylurus and male C. pumilus, raised their interaural crest during different social interactions. The ability of both species to distinguish between males and females and roostmates from strangers in scent-choice experiments was tested in the field. 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 trial. There is some indication that roostmate recognition may vary inversely with test-subject colony size suggesting that recognition is individually based. The presence of osmetrichia 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.