Effect of artificial light on activity in frugivorous bats (Pteropodidae)

Artificial lighting at nights (ALAN) affects behaviour in many animals, especially nocturnal species. However, its effect on frugivorous bats remains less explored, especially in the family Pteropodidae. Since they rely predominantly on vision and light-based cues, ALAN at roost sites could have consequences on their behaviour, activity, and the ecosystem services they provide. In a semi-urban site in southern India, we compared the emergence-return activity of the cave-roosting Rousettus leschenaultii, between a roost in an undisturbed, naturally-lit agricultural well and an artificially-lit roost in a temple. We also compared emergence times between five colonies of the tree-roosting Pteropus giganteus (currently P. medius) that were exposed to different intensities of artificial light. Emergence-return flights at the naturally-lit R. leschenaultii roost occurred significantly earlier than at the artificially-lit roost. Peak flight activity across nights varied more in the naturally-lit than at the artificially-lit roost. Nightly flight durations (interval between peak emergence and peak return times) varied more in the naturally-lit roost, while mean flight durations were similar between these roosts. In P. giganteus, emergence was significantly earlier in the highly light-polluted roost than in the other roosts. These modified flight activities could have potential consequences on the physiology and ecology of fruit bats and requires further study. Moreover, the effect of ALAN on seed dispersal and pollination services provided by fruit bats in tropical landscapes remains to be understood.