Population Dynamics of the Bat Pipistrellus Subflavus

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Abstract
Populations of pipistrels hibernating in two West Virginia caves were studied over a 14-year period. Methods are developed for determining the percentages of surviving bats not recaptured in the caves, the annual survival percentages, survival rates for each sex and age group and the structure of the populations by age and sex. Sex ratios observed in the caves, which fluctuate between 69.5% and 85.1% males, do not show the sex ratio of the species; analysis of survival rates indicates that the true sex ratio is 61♂: 39♀. Life tables are presented for the species and for random cohorts of adults. Annual survival rates are different for each age group. Survival is low in youngest bats, climbs to a peak at 3.5 years and then decreases, falling rapidly as maximum life span is approached.