Species Assessment For Townsend’s Big-Eared Bat (Corynorhinus [=Plecotus] Townsendii) In Wyoming
Author(s):Publication Date: 2003-12
Douglas A Keinath
Tags: BLM, WLCI Agency Report, WLCI
The western subspecies of Corynorhinus, C. townsendii pallescens and C. t. townsendii are not
currently federally listed or candidate species throughout their range. Two eastern subspecies, C.
townsendii ingens and C. townsendii virginianus, are currently listed as Endangered by the U.S.
Fish and Wildlife Service. Both Regions 2 and 4 of the Forest Service and the Bureau of Land
Management in Wyoming and Colorado list the full species as sensitive within their jurisdictions.
The Bureau of Land Management in South Dakota, Nebraska and Kansas apparently does not
provide any special protection for the bats. The Wyoming Natural Diversity Database lists it as
being of particular conservation concern as indicated by its S1 ranking. The state heritage ranks
for C. townsendii in the other Rocky Mountain states range from S1 to S3 (Table 1), reflecting the
rarity and vulnerability of the species in those states. The Wyoming Game and Fish Department
considers C. townsendii to be category 2 Native Species Status (NSS2), while none of the other
states neighboring Wyoming confer any special status to the bat beyond Natural Heritage ranks.
Although C. townsendii is found throughout most of the western United States, including
British Columbia, central Mexico and the Baja Peninsula, it appears to be relatively uncommon
throughout its range. C. townsendii is a cavernicolous species, meaning that it relies on cave-like
structures for shelter during all portions of its life cycle. Though there are reports of cavernicolous
species occasionally using hollows in large trees or abandoned buildings, caves and mines remain
essential landscape features to C. townsendii and for other species of bats that use caves and mines
during various stages of their life cycle. Reliable data on the abundance of C. townsendii, as with
most species of bats, is lacking. However, there is general concurrence amongst bat biologists that
there has been a downward trend in abundance of the species over the past half century. This
trend is attributed primarily to renewed mining at historic sites, the closure of tens of thousands ofGruver and Keinath
abandoned mines without consideration of their habitat potential, and direct and indirect
disturbance by human visitors at caves and mines.
C. townsendii is particularly sensitive due to a variety of intrinsic biological factors including
its habitat specificity, fragmented distribution, low reproductive rate, and intolerance of direct
disturbance. The primary threats throughout the Rocky Mountain region are closure of abandoned
mines, renewed mining at historical sites, recreational caving, and conversion and alteration of
roosting and foraging habitat. Therefore, the primary conservation considerations are: 1) the
preservation and protection of suitable maternity roosts and hibernacula, and 2) the maintenance of
suitable landscape components (i.e., foraging, commuting, and drinking habitat) near these roosts.