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Townsend's Big-eared Bat
Corynorhinus townsendii
NatureServe conservation status
Global (G-rank): G4
State (S-rank): S3
External links
Species range
The western range of Townsend’s big-eared bat spans from the Pacific Ocean to the western Great Plains and from central Mexico to southern British Columbia (Kunz and Martin 1982). In Utah, it is found across various habitats, though its distribution is locally influenced by the availability of caves and mines, where the species tends to concentrate (Oliver et al. 2000, Sherwin et al. 2003).
Habitat
This species occurs in a wide variety of habitats including sagebrush steppe, pinyon-juniper, mountain shrub, and mixed conifer associations. The primary habitat component, however, is the availability of caves or mines for roost sites. Because required roost conditions vary seasonally and individuals typically do not move long distances between roost sites, highest population densities generally occur in areas with complexes of mines or caves offering diverse roost habitat conditions.
Ecology
The Townsend’s big-eared bat is dependent on caves and mines for its habitat, with their availability determining local population status (Sherwin et al 2003, Hayes et al. 2011, Kunz and Martin 1982, Pierson 1999). The bats prefer larger, more complex caves and mines due to their variable conditions (Gruver and Keinath 2006). Surveys indicate about 20% of abandoned mines in Utah show evidence of use by this species. For foraging, the bats use diverse habitats but favor forests, forest edges, and riparian zones, especially near cave and mine resources (Kunz and Martin 1982, Pierson et al. 1999, Gruver and Keinath 2006). This sedentary species forages close to roosts and is a slow, maneuverable flyer, likely gleaning vegetation and catching prey in flight (Kunz and Martin 1982, Gruver and Keinath 2006). Like all Utah bats this species is an insectivore, but generally specializes on moths.
Threats or limiting factors
Threats to Townsend’s big-eared bat include the loss of cave and mine roosting sites and human disturbance at these locations (Pierson et al. 1999, Sherwin et al. 2003, Gruver and Keinath 2006). The Utah Division of Oil Gas and Mining conducts surveys prior to abandoned mine closures and protects those sites with substantial bat use. Caves, which are crucial for maternity colonies and hibernacula, are preferred roosting habitats and support larger concentrations than mines (Sherwin et al. 2000, Sherwin et al 2003, Pierson et al. 1999, Hayes et al. 2011). Increased recreational caving poses a risk, as these bats often roost in accessible areas, and instances of human-caused mortality have been documented (Sherwin et al. 2000, Hayes et al. 2011, Oliver et al. 2000). Pesticide use for agricultural and forest pests, which are primary prey for the bats (moths), decreases forage and may expose bats to toxins (Kunz and Martin 1982, Pierson et al. 1999).
