In colonial tree-dwelling bats, is vital to prevent disintegration of the group during frequent roost-switching. Thus some mechanisms which maintain group cohesion are expected. Dawn swarming is a set of behavioural displays observed in many such bats before they enter the roost. It is suggested that this behaviour plays a role in transferring information about the roost position. However this phenomenon had not been explored in detail. Based on qualitative and quantitative description of behaviour we suggest its potential function. Using field-based video-recordings of swarming sessions made on maternity colonies of Leisler's bat (Nyctalus leisleri), we constructed ethograms which revealed remarkably similar behavioural sequences among individuals. For more than two hours prior to sunrise, individual flybys in front of the roost entrance predominated, followed by landings and leaps, which preceded the final entering of the roost. Interestingly, no obvious peak of behavioural activity was found at any particular time during swarming but a wave-like pattern was observed. We suggest that individuals are swarming in close proximity to the roosting tree with some purpose, most probably serving as a beacon for other group members and thus marking the current location of the roost.
Rapid range expansion of Kuhl's pipistrelle (Pipistrellus kuhlii) has been observed throughout Europe, and in addition to its natural habitats of temperate grasslands and agricultural areas, the species is common in city centres, where it roosts in human-made structures. It has been suggested that the flexibility of this species in regard to different human-induced changes, such as climate change and urbanization, is responsible for the apparent range shift. Although P. kuhlii exhibits one of the highest degrees of synanthropy among bat species in Europe, its ecology has thus far not been thoroughly studied. This study aims to describe its foraging and roosting selection in Central Europe (eastern Slovakia), where the northernmost maternity colony of P. kuhlii roosts in human settlements. Radio-tracking was conducted during the pre-parturition and post-lactation periods. We identified six artificial roosts within the study area that were interlinked, with bats switching between them. Ten individuals were used for modelling foraging-habitat utilization, which revealed that bats were highly selective. The only habitat type that bats clearly preferred, regardless of season, was an urban illuminated area close to a river. Only slight avoidance — of open areas — was observed during the pre-parturition period.
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