DOES CALCIUM CONSTRAIN REPRODUCTIVE ACTIVITY IN INSECTIVOROUS BATS - SOME EMPIRICAL-EVIDENCE FOR SCHREIBERS LONG-FINGERED BAT (MINIOPTERUS-SCHREIBERSII)

Insects are a poor source of dietary calcium and since they are season ally abundant, it has been suggested that calcium availability may pla y a significant role in controlling the timing of reproduction in inse ctivorous bats. To assess the possible role of dietary calcium, we hav e measured bone calcium concentrations in female and male long-fingere d bats (Miniopterus schreibersii) through a full reproductive cycle. T he results indicate that winter was not a period of calcium stress and , therefore, that seasonal changes in insect abundance and dietary cal cium availability are not a satisfactory explanation for the occurrenc e of delayed implantation in the long-fingered bat. Bone calcium conce ntrations of females did not differ significantly throughout pregnancy , indicating that the insects available in winter and early summer wer e sufficient to meet the calcium demands of pregnancy. Lactating femal es had the lowest bone calcium concentrations of all specimens, suppor ting the suggestion that lactation is indeed a period of severe calciu m stress in aerial insectivores. We conclude that parturition is proba bly timed so that lactation coincides with the period of maximal insec t abundance and corresponding dietary calcium availability.