A small-scale response of urban bat activity to tree cover

Bats in urban areas depend on trees, and bat activity increases with tree cover. To effectively manage bat habitat in cities, it is important to know the distance to which tree cover most strongly influences bats (i.e., the ‘scale of effect’). The aim of this study was to estimate the scale of effect of tree cover on bats in Toronto, Canada. To achieve this, we measured bat activity at 52 sampling sites across the city. We then examined the relationships between bat activity and percent tree cover measured within each of 19 scales, 0.025 to 3.5 km in radius, surrounding each sampling site. We found that the scale of effect of percent tree cover on total bat and individual species activity ranged from 0.025 to 0.25 km among species. Our results suggest that adding or removing urban trees influences bats up to 0.25 km away. Urban tree management decisions should consider the impacts to bats beyond the site of management and within the surrounding landscape of a 250 m-radius scale.