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Species Assessment For Townsend’s Big-Eared Bat (Corynorhinus [=Plecotus] Townsendii) In Wyoming

Publication Information

Author(s):
Douglas A Keinath
Jeffery Gruver
Publication Date: 2003-12
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. 

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