Activity patterns of two syntopic and closely related aerial-hawking bat species during breeding season in Białowieża Primaeval Forest

Temporal and spatial activity of bats is species specific and shaped by many factors such as energy requirements, climate conditions and food distribution. Pregnancy and lactation are the most energy-demanding periods throughout the female life cycle. During these periods, females have to optimize their activity patterns to maximize foraging success; however, they simultaneously need to take care of their young. In addition, daily and seasonal fluctuations of insect availability strongly affect bat foraging activity. If females, which are under strong energy constraints, belong to closely related species, they may potentially suffer from competition. One of the mechanisms that allows them to avoid competition is temporal and spatial niche partitioning. Noctule and Leisler’s bats are closely related forest-dwelling species whose diet is similar and consists mainly of ephemeral insects. The aim of our study was to test if they exhibit similar patterns in relation to the time and duration of their nocturnal activity. In Bia?owie?a Forest, we demonstrated that female nocturnal activity of both noctule and Leisler’s bats was shaped mostly by reproductive period and ambient temperature. We did not observe significant differences in the activity patterns of the two noctule species, which suggests that physiological constraints connected with reproduction and environmental conditions affect these species in a similar way and outweigh the competition between species.