Survival and roost-site selection in the African bat Nycteris thebaica (Chiroptera : Nycteridae) in Swaziland

Survival and mortality of African bats is poorly known. A banding Study of a population of Nycteris thebaica, roosting in 15 road culverts in north-eastern Swaziland, was initiated in 1998. Since then, a total of 799 bats have been banded including five cohorts of same-aged individuals of known age. Cohort life-tables and survivorship Curves were calculated using these data. For both males and females, survivorship was low in the first year, but increased thereafter. Approximately 15\% of females and 10\% of males banded as juveniles in 1998 and 1999 survived to three years of age. Of female bats banded as adults in July 1998 (n = 39), 23\% had survived to January 2003 (4.5 years). The corresponding value for males (n = 6) was zero. Of 28 male bats banded in 1998, only one (4\%) was recaptured after four years. Female values probably reflect true survival and mortality, whereas, dispersal and movement complicate the values for males. Female Nycteris thebaica did not randomly select roosting sites. The 15 Culverts were occupied by six discrete groups of female bats. The presence of male bats at the study site was irregular, with movements of 9 km having been recorded by one particular individual.