Unfortunately, land-use practices that prohibit persistence or development of older stands of forest may remove snags and other high-quality roosting sites (Campbell et al. Under natural conditions roosts in tree cavities can already be a limiting resource for populations because their availability to wildlife varies over time and depends on a continuing supply of suitable trees (Bonar 2000).
Colonies of bats are more likely to be social units than simple aggregations of conspecifics that co-occupy a roost at a given time (Fenton 2003), and 1 cavity within a particular tree might not be sufficiently large to accommodate all members (Willis et al. Given these factors, the life histories and social behavior of cavity-roosting bats might require their frequent movement among roosts (O'Donnell 2000).
We returned to the bridge at which the bat was found and listened for the bat's signal using a model TRX1000S radioreceiver (Wildlife Materials, Inc., Carbondale, Illinois) and a 3-element y agi antenna.
On several occasions we preferentially radiotagged some individuals over others to ensure that both sexes were represented in our sample and that individuals captured at different bridges were monitored.
For all bats that we captured, we measured mass and forearm length and determined their sex, reproductive condition if female (pregnant, lactating, or nonreproductive), and age-class (juvenile or adult, based on ossification of epiphyseal joints of the phalanges [Anthony 1988]).
Crevice-and cavity-roosting bats often show loyalty to patches of habitat where dead or senescent trees are concentrated, especially where such structures are located≤ 1 km apart (e.g., Kurta et al.
2002; Sasse and Pekins 1996; Vonhof and Barclay 1996; Weiler and Zabel 2001).
To reduce disturbance to maternity colonies, we timed capture attempts to not coincide with parturition or the approximately 3 weeks after this event before young could fly (Trousdale and Beckett 2004).