Ecology and ecophysiology of social structure and population dynamics in bats (Vespertilionidae)

Abstract

Worldwide, bats are in decline with populations under threat from many pressures, including habitat loss, disease and climate change. A detailed understanding of bat social structure and population dynamics is needed to understand and tackle this decline. Yet despite bats representing around twenty percent of all mammalian diversity, they are underrepresented in life history studies, restricting our understanding of social associations, spatial patterns and mating systems for many species. This, in turn, inhibits efforts to conserve species and restricts interpretation of their population dynamics.
This study, therefore, aimed to analyse the ecology of social structure and population dynamics using long-term ringing data from several British bat species: Natterer’s bats (Myotis nattereri), brown long-eared bats (Plecotus auritus), Pipistrellus spp. (P. pipistrellus and P. pygmaeus) and Bechstein’s bats (Myotis bechsteinii).
Analysis of long-term data of M. nattereri and P. auritus revealed that bats maintain long-term associations persisting over several years. Spatial patterns revealed high fidelity to roost sites. However, on occasions when bats were disturbed during ringing, their dispersal patterns suggested that bats possess a wide knowledge of alternative roost sites which may facilitate relocation following habitat or climate change.
Analysis of population dynamics and social structure of three sympatric species (M. nattereri, P. auritus and Pipistrellus spp.) revealed that social systems vary between species and seasons. Large roosting groups were reported for M. nattereri and P. auritus. Males were found to roost with females both pre- and post-parturition, however populations were female-biased for both species. Solitary male Pipistrellus spp. found pre-parturition were joined by an influx of predominantly new adult females for the formation of mating groups post-parturition. There was no preference for roosting in boxes facing North, South-east or South-west for any species. Roosting groups of M. nattereri persisted from pre- to post-parturition whilst the abundance of P. auritus found in boxes post-parturition was low, suggesting alternative roosting behaviour for this species post-parturition perhaps due to increased activity at swarming sites. Increasing population trends were reported for M. nattereri and Pipistrellus spp. whereas the pre-parturition population of P. auritus showed a moderate decline, the cause of which requires further investigation.
Survival analysis revealed female-biased survival rates for M. nattereri and P. auritus. Cohort variation in juvenile survival was found in female M. bechsteinii whereby high rainfall during the lactation period and an additive effect of high population density resulted in lower survival. Age of first reproduction varied between one and five years for this species, but did not vary between cohorts with the majority of females reproducing for the first time aged two years.
Furthermore, an ecophysiological field study revealed no effect of social structure or roost microclimate on the metabolic rates of free-ranging M. nattereri. However, low metabolic rates indicated torpor was frequently used both pre-and post-parturition.
The results of this study suggest that future studies on population biology should take an integrated approach incorporating aspects of both ecology and ecophysiology for the conservation of a species, especially in the face of climate change.

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Identifiers

ORCID for Philip L. Newland: orcid.org/0000-0003-4124-8507

ORCID for C. Patrick Doncaster: orcid.org/0000-0001-9406-0693

ORCID for Alex R. Kraaijeveld: orcid.org/0000-0002-8543-2640

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