Bats in Temperate Forests: Where Are the Trends in Bat Populations?

Abstract

Understanding bat population dynamics is crucial to evaluating the effects of forest disturbances, however this remains a significant knowledge gap in bat ecology. In this chapter, we review different approaches to long-term studies of bat populations in temperate forests including landscape-scale monitoring programs and localized mark-recapture studies of banded bats. We particularly focus on studies that assess long-term changes to populations in managed forests, given that these forests offer opportunities to experimentally test bat response to disturbances via forest management treatments. We reviewed available NASBR abstracts from 1970 to 2018 to highlight trends in North American bat population research. While use of acoustic detectors has increased the ease with which researchers can conduct landscape-scale studies, these methods are limited to generating relative population indices (e.g. activity, occupancy) as individual bats are not identified. However, as use of acoustic methods continues to grow, use of mark-recapture studies, which allow researchers to measure bat population size and demographic rates, has decreased. Furthermore, the majority of studies of bats in forests do not extend past 1 year. When investigating ongoing effects of disturbance on bats in forests, large-scale long-term studies using population indices are needed to track trends at large spatial scales, and to capture unpredictable events like fire, drought and flood. Landscape-scale studies can also incentivize more localized experimental mark-recapture studies, ideally in partnership with forest managers. We highlight several long-term studies at the landscape and localized scales that have helped us better understand bat population dynamics in managed forests. We also highlight fire (wildfire and prescribed) as another key forest disturbance that should be the subject of ongoing studies for bats. Long-term research is vital for understanding long-lived, dynamic systems like forests, yet for bats, such research is notably scarce.