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

Abstract

Several bat species occur in piñon (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. Piñon‐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 17.8 m of the roost site. Preference by lactating females for rock roost sites increased with the number of available rock roosts within 5 m 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 5 m of the roost site, decreased with distance from water, and increased with area of pre‐settlement juniper woodland within 1 km 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. © 2018 The Wildlife Society.

Differential selection of roosts by Eastern Small-footed Myotis (Myotis leibii) relative to rock structure and microclimate

“…Water loss from evaporative cooling can be substantial for bats, and severity of water loss can differ based on roosting habitat (Noakes et al 2021). The costs of evaporative water loss for bats in rock-roosts compared to other roost types might explain why proximity to water has often corresponded with roost selection at the landscape scale, and perhaps why some species select different roost types in some parts of their range (Solick and Barclay 2007; Snider et al 2013; Anthony and Sanchez 2018). Additional study of this topic is warranted given that many species of rock-roosting bats occur in arid regions and declining water availability is expected to impact their populations (Adams and Hayes 2008; O'Shea et al 2011).…”

Use of predictive distribution models to describe habitat selection by bats in Colorado, USA

“…; Cook et al 2017). Bat and songbird species associated with this land cover should be considered when developing such treatment prescriptions (Lukacs et al 2015, Anthony and Sanchez 2018, Navo et al 2018.…”

Bruneau-Owyhee sage-grouse habitat project (BOSH) : final environmental impact statement /

“…In a study completed in pinyon-juniper woodlands, Snider et al (2013) found that tree roosts were not a vital resource for reproductive females of long-eared myotis. Both Snider et al (2013) and Anthony (2016) documented that females with young prefer rock crevices for maternity roosts, which typically range between 12 and 30 females (Manning and Jones 1989). Male long-eared myotis appeared to roost more equally between rock crevices and trees (Anthony 2016).…”

“…Both Snider et al (2013) and Anthony (2016) documented that females with young prefer rock crevices for maternity roosts, which typically range between 12 and 30 females (Manning and Jones 1989). Male long-eared myotis appeared to roost more equally between rock crevices and trees (Anthony 2016). Long-eared myotis that chose juniper for roost sites used old growth trees that were > 150 years old.…”

“…When bats do utilize trees, they generally use trees with cavities or sloughing bark, which are usually only present in old growth and decadent juniper. Old growth juniper with at least one cavity were those used by long-eared myotis in eastern Oregon (Anthony 2016). Because old growth juniper would not be cut, there would be a negligible loss of tree roosting habitat.…”