Patterns of survival and roost switching in an African insectivorous bat

Abstract

Variation in survival over time and amongst age and sex classes drives population dynamics for a large majority of long-lived species and is critical to understanding species demography. For highly mobile species that actively move among potential breeding locations, coupling survival information with estimates of locational fidelity provides the basis for our understanding of species population dynamics. We studied the effect of time, age and sex class, and climatic variables on survival and roost transition probabilities on a population of Egyptian slit-faced bats in Swaziland from 1450 marked individuals from 16 roosts over a 10 year period. We then used variance components analysis to estimate average annual survival and associated temporal process variance. Annual apparent survival varied with sex and age, being highest in adult males and lowest in juvenile females. We did not find evidence of survival being influenced by climatological factors as commonly observed in temperate bats. Roost switching occurred frequently, with more transitions to roosts harboring larger number of bats. Furthermore, the probability of transitioning to another roost was related to its distance from the original roost. The dispersal patterns revealed in this study were consistent with the fission-fusion dynamics common for colonial bats.