Seasonal variation in emergence and activity pattern at roosting site of lyle's flying Pteropus lylei Andersen, 1908 at Pho, Chachoengsao province

Abstract

This study addressed the question of how environmental factors influence the variation in emergence and daytime behavior of Lyle's flying fox, Pteropus lylei. Therefore, the colony-wide emergence, environmental factors and daytime behavior were investigated directly at roosting site of Lyle's flying fox (Wat Pho, Amphoe Bang Khla, Chachoengsao Province) for 12 months. It was found that the onset of colony-wide emergence time had significantly affected by sunset time and relative humidity. The duration of colony-wide emergence varied throughout the year, and tended to increase during parturition and early lactation periods. However, the duration was weakly correlated with seasonal change in twilight duration, and lunar phase had no influence on the colony-wide emergence of Lyle’s flying fox. The observation on individual emergence was conducted by filming. The results showed that males, female and juvenile tended to emergence later during reproductive periods, especially in parturition and early lactation. During that time, lactating females were the last to emerge. The later emergence of lactating females can be reflected from the enlargement of wing loading, which reduce flight performance and increase risk of predation. In conclusion, environmental factors and reproductive status play as crucial roles in emergence of Lyle's flying fox. From daytime behavior observations using scan-sampling technique, the most common behaviors performing by bats were sleeping, grooming and wing flapping. Variation in sleeping, grooming, wing flapping and mating/courtship between times of day and times of the year were apparently observed. Furthermore, wing spreading, movement and mating/courtship were observed in males more frequently than in females, whereas females exhibited grooming and aggressive behaviors more frequently than males. In conclusion, time of day, season and sex have influence on daytime behavior of Lyle's flying fox.