Bat activity in forest margins : canopies, edges, seasonality, and competition.

Abstract

Forest edges provide open space that bats often use to travel and forage. As another type of margin, forest canopies provide similar structural space for bat activities. Such margins may supply bats in forests with the structural resources they require, such that some species could compete over edge space as a preferred habitat type. This project examined the role of forest canopies and edges as an important habitat type for bats through the observation and examination of bat activity levels. Bat communities in the Rocky Mountains of northern Utah (summers 2008-2009) and the pineywoods of eastern Texas (fall 2009 and spring 2010) were observed through the use of Anabat SD1 bat detectors. Activity levels of bats in Utah were much higher in forest edges than in canopies. This phenomenon appears to have a strong seasonal component, during which period competition over edge resources intensifies between high and low frequency guild bats. In the pineywoods of eastern Texas, bat activity levels also differ between canopies and edges, but bats in this habitat seem to shift seasonally between margin types. These shifts may coincide with seasonal migrations of some bat species. Future research would further investigate seasonality in bat activity, and better define the role of clutter in bat activity in forest margins.