Roost site selection of western long-eared myotis in a western juniper woodland

摘要

Several bat species occur in pinon (Pinus monophylla) and juniper (Juniperus ssp.) woodlands across the western United States, yet factors influencing roost site selection in these vegetation communities are poorly understood. Pinon-juniper woodlands have expanded beyond their historical geographic range in the western United States since European settlement. Many former stands of widely spaced old-growth juniper are now crowded with younger trees. Currently, federal and state land management agencies and private landowners are removing juniper trees to restore shrub-steppe for greater sage-grouse (Centrocercus urophasianus) across its geographic range, with little understanding of the treatment effects on roost site selection by bats. We used radio-telemetry to examine roost site selection of western long-eared myotis (Myotis evotis) at 3 spatial scales (roost, plot, and home range) during the breeding season. We attached radio-transmitters to 32 individuals and located 92 day roost sites for 25 different individuals. Lactating females selected rock crevices as roosts more frequently than tree cavities, whereas males used tree roosts and rock roosts more evenly. The majority of tree roosts were in pre-settlement trees that had at least 1 cavity. The odds that a tree was selected as a roost site increased with the number of available tree roosts within 17.8m of the roost site. Preference by lactating females for rock roost sites increased with the number of available rock roosts within 5m of the roost site and decreased with distance from water. Preference by males for rock roosts decreased if the roost was a single rock compared to an aggregate of rocks, increased with the number of available roosts within 5m of the roost site, decreased with distance from water, and increased with area of pre-settlement juniper woodland within 1km of the roost site. These results provide support for protecting pre-settlement juniper trees and rock formations near water sources in juniper woodlands to conserve existing populations of western long-eared myotis during the breeding season. (c) 2018 The Wildlife Society.