Townsend's Big-eared Bat (Corynorhinus townsendii)
- Protection Status Notes
- USFWS former category 2 candidate. Considered Sensitive by the U.S. Forest Service. It is listed as a Species of Special Concern by Texas Parks and Wildlife, the Department of Fish and Game in California, and is considered a Species of Special Concern due to declining populations and limited distribution in Utah.
- Corynorhinus townsendii can be distinguished from all other vespertilionids by the presence of prominent, bilateral nose lumps, and large ears.
- Life History
- Summer maternity colonies range in size from a few dozen to several hundred individuals. Maternity colonies form between March and June (based on local climactic factors), with a single pup born between May and July. Males remain solitary during the maternity period. Winter hibernating colonies are composed of mixed-sexed groups which can range in size from a single individual to colonies of several hundred animals (or in some areas, particularly in the eastern U.S., several thousand). Mating generally takes place between October and February in both migratory sites and hibernacula. Seasonal movement patterns are not well understood, although there is some indication of local migration, perhaps along an altitudinal gradient.
Its habit of roosting on open surfaces makes it readily detectable, and it is often the species most frequently observed (commonly in low numbers) in caves and abandoned mines throughout its range. It has also been reported to utilize buildings, bridges, rock crevices and hollow trees as roost sites.
Foraging associations include: edge habitats along streams and areas adjacent to and within a variety of wooded habitats. Eastern populations have been detected foraging in agricultural fields. It often travels large distances while foraging, including movements of over 10 miles during a single evening. It is a moth specialist with over 90% of its diet composed of lepidopterans.
- Habitat associations include: coniferous forests, mixed meso-phytic forests, deserts, native prairies, riparian communities, active agricultural areas, and coastal habitat types.
- C. townsendii occurs throughout the west, and is distributed from the southern portion of British Columbia south along the Pacific coast to central Mexico and east into the Great Plains, with isolated populations occurring in the south and southeastern United States. It has been reported in a wide variety of habitat types ranging from sea level to 10,800 feet. Distribution is strongly correlated with the availability of caves and cave-like roosting habitat, with population centers occurring in areas dominated by exposed, cavity forming rock and/or historic mining districts.
In Texas, suitable habitat supports this species in the western one-half of the state.
- Threats and Reasons for Decline
- The primary threat to C. townsendii is almost certainly disturbance or destruction of roost sites (e.g., recreational caving, mine reclamation, renewed mining in historic districts). Surveys conducted in Oregon and California indicate that historic roost sites nave been negatively impacted in recent years with most reported colonies exhibiting moderate to sizable reduction in numbers. Addition surveys in Utah indicate that several historic maternity sites have been abandoned, although it is no known if these colonies have relocated. This species is very sensitive to disturbance events and has been documented to abandon roost sites after human visitation. In California and at a number of sites in the east, depressed populations have recovered with the protection (i.e., gating) of roosts. In large portions of its western range, dependence upon abandoned mines puts this species at risk if mine reclamation and renewed mining projects do not mitigate for roost loss or do not conduct adequate biological surveys prior to mine closure. Both roosting and foraging habitat my be impacted by timber harvest practices. Pesticide spraying in forested and agricultural areas may affect the prey base.
- Ongoing Recovery
- Locating and protecting key cave and mine roosts are the key activities needed for Townsend's big-eared bat conservation. Mines should be surveyed for bats before closure. Bat-friendly gates can prevent hazards to humans and human disturbance of roosting sites in caves and mines.
- Identification and protection of significant roost sites is still needed in most areas. Significant populations need to be monitored over time. More information is needed on foraging requirements, seasonal movement patterns, and population genetics (i.e. the degree of relatedness within and between different maternity roosts).
Additional details can be found in the online version of The Mammals of Texas for the Townsend's Big-eard Bat