Ambient temperature is more important than food availability in explaining reproductive timing of the bat Sturnira lilium (Mammalia: Chiroptera) in a montane Atlantic Forest

Abstract

Reproduction of bats is determined by a suite of endogenous and exogenous factors. Among exogenous influences, special attention has been given to the influence of food availability. However, in highland forests, severe decreases in temperature during the cold and dry season may also play an important role. In the present study we tested the influence of ambient temperature and food availability on the timing of reproduction in the frugivorous bat Sturnira lilium (E. Geoffroy, 1810). We conducted a 15-month mist-netting sampling in a mountain area of the Brazilian Atlantic Forest during which time we assessed the bats' diet through fecal samples, monitored fruit production of the main food plants, and recorded variations in ambient temperature. Sturnira lilium fed almost exclusively on Solanaceae. Similarly to the lowlands, reproduction was bimodal, but reproductive season tended to be shorter in the highlands and peaked in the warmer months of the year. Overall, 44% to 53% of the reproductive pattern was explained by variations in ambient temperature, while the relationship with food availability was nonsignificant. We conclude that variations in ambient temperature in tropical mountains may be a stronger selection pressure than food availability in determining reproductive timing of bats.