2003 study of bat roosts, John Day Fossil Beds National Monument

Rodhouse, Thomas; Wright, R

The primary goal of the study was to determine the location, size, and physical characteristics of maternity colonies for four bat species of concern in and adjacent to the monument. The four target species were the pallid bat, Townsend’s big-eared bat, western small-footed myotis, and the silver-haired bat. Each of these species are listed by state and federal agencies as species of concern. Additional goals included the collection of information on the foraging behavior of the western small-footed myotis and the spotted bat. Radio transmitters were attached to 10 female pallid bats, 9 female small-footed myotis, 7 silver-haired bats, and 2 spotted bats. Townsend’s big-eared bats were difficult to capture and no transmitters were attached to individuals of that species. Forty-five pallid bat day roosts and 52 small-footed myotis day roosts were located during the study. Silver-haired bats and spotted bats were difficult to track and likely were transient through the area. Only one male silver-haired bat remained in the area for 1 week and roosted in the top of a tall cliff complex. Pallid bats roosted in the largest south-facing cliff complexes available. Small-footed myotis roosted in cliffs and rock outcrops, but were less selective about roost structures. Pallid bat roosts were significantly taller than myotis roosts and were closer to capture locations. Small-footed myotis traveled up to 12 km between roosts and foraging areas. Both species exhibited strong fidelity to roost areas but switched roosts within areas frequently. Small-footed myotis showed strong fidelity to foraging areas located along agricultural fields and riparian areas. Pallid bats roosted in large maternity colonies of 22-120 bats and emerged from roosts after dark. Small-footed myotis roosted alone or in small clusters and emerged quickly after sunset.

2003 study of bat roosts, John Day Fossil Beds National Monument

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