. The Canadian field-naturalist. Natural history. 24-l\/br 15-Apr OS-IVby 04-Jun 22-Jun 06-Jul 28-Jul 10-Aug23-Aug07-Sep DATE Figure 1. Seasonal use of an abandoned mine used as a night roost by three species of bats in western Maryland during the 2000 foraging season. ed with ambient temperature (r = , P < ; Figure 2). Many studies have reported a positive relationship between bat foraging activity and ambi- ent temperature (, Lacki 1984; Hayes 1997; Gaisler et al. 1998). Anthony et al. (1981) found an inverse relationship between ambient temperature and the length of night-roo
. The Canadian field-naturalist. Natural history. 24-l\/br 15-Apr OS-IVby 04-Jun 22-Jun 06-Jul 28-Jul 10-Aug23-Aug07-Sep DATE Figure 1. Seasonal use of an abandoned mine used as a night roost by three species of bats in western Maryland during the 2000 foraging season. ed with ambient temperature (r = , P < ; Figure 2). Many studies have reported a positive relationship between bat foraging activity and ambi- ent temperature (, Lacki 1984; Hayes 1997; Gaisler et al. 1998). Anthony et al. (1981) found an inverse relationship between ambient temperature and the length of night-roosting bouts by female Little Brown Bats, and a positive relationship between ambient temperature and total insect densi-. AMBIENT TEMPERATURE (X) Figure 2. Relationship between capture success (number of bats / trap hour) at the abandoned mine night roost and ambient temperature on 19 nights from 4 April to 7 September 2002. Ambient temperature repre- sents the average of three nightly measurements. ty. These data indicate that foraging activity by Little Brown Bats decreases at low temperatures when foraging conditions are poor. In our study, it is possible that the relationship between capture suc- cess at the night roost and ambient temperature reflected different levels of foraging activity in response to variable insect densities (, many bats remained in day roosts at low temperatures). Our limited data also support the findings of Grinevitch et al. (1995) that male and nonreproductive female Big Brown Bats do not forage at ambient tempera- tures < ~12°C (Figure 2). More work is needed on the night-roosting behav- ior of temperate-zone bats (Adam and Hayes 2000). In many areas, night roosts need to be located and documented for this research to progress. Although the data presented here were collected from a single mine, we emphasize the potential value of aban- doned mines to bats, and efforts to salvage and pro- tect these structures should continue or be initiat
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