54 
PROCEEDINGS OF THE CALIFORNIA ACADEMY OF SCIENCES 
Series 4, Volume 65, Supplement I 
about 1,300 meters in pinon-juniper habitat in Mohave County, northwestern Arizona during 1959 
(Cockrum et al., 1996). Only a single maternity colony is now known from old mines along the 
Lower Colorado River in California, where colonies in other mines known historically have dis¬ 
appeared (Brown, 2013). One factor implicated in these losses along the river is suspected reduc¬ 
tions in availability of insect prey associated with loss of native vegetation to agriculture and the 
concomitant intensive use of insecticides (Brown, 2013). 
Additional detailed accounts on past status of numerous colonies of Townsend’s big-eared bats 
are given in a state-by-state review conducted during the late 1990s (Pierson et al., 1999). Sizes of 
colonies known at the time were included, as were changes in use and counts in comparison with 
past results, and identification of likely causes for declines and present levels of protection. Most 
of the information supports the perception of serious declines in western populations of this species 
(Pierson et al., 1999). Sites identified in the report by Pierson et al. (1999) may be useful to re-visit 
to determine current status. 
Population Genetics: Despite threats and evidence of past declines in local populations, 
genetic diversity is not dangerously low in C. townsendii pallescens nor in C. townsendii 
townsendii (Piaggio et al., 2009) perhaps with exceptions in some localized areas (Smith et al., 
2008). However, Lack and Van Den Bussche (2009) tentatively concluded that the current popula¬ 
tion size inferred from genetic measures may be declining when compared to genetic estimates of 
past population growth over the recent evolutionary history of the species. 
Management Practices and Concerns. — A detailed plan specifying threats to populations 
of Townsend’s big-eared bats and management practices for their amelioration can be found in the 
conservation strategy prepared by Pierson et al. (1999). The strategy also includes recommenda¬ 
tions for roost surveys, inventory and monitoring, protocols for evaluating use of abandoned mines 
as bat roosts, and examples of effective gate designs. 
White-Nose Syndrome: Eastern subspecies of Townsend’s big-eared bats (Virginia big-eared 
bat and Ozark big-eared bat) presumably have been exposed to the fungus that causes white-nose 
syndrome for several years after the epizootic reached their populations (Johnson et al., 2012b; 
Arkansas Game and Fish Commission, 2014). Antibodies to the fungal agent of white-nose syn¬ 
drome were not detected in three individuals sampled during 2011 in western Oklahoma, consis¬ 
tent with an absence of reports of gross lesions or mortality in the region at the time (Brennan et 
al., 2015). Even after P. destructans was genetically detected on a western subspecies of 
Townsend’s big-eared bats in Texas during 2017, clear indications of mortality or clinical signs of 
disease were not observed (Texas Parks and Wildlife, 2017). Fungal presence without obvious indi¬ 
cations of deleterious disease effects have been noted in eastern subspecies of this bat for several 
years, and it has been suggested these bats have behavioral or physiological strategies for surviv¬ 
ing white-nose syndrome (Johnson et al., 2012a; Coleman and Reichard, 2014). It remains 
unknown whether western subspecies of Townsend’s big-eared bats will show similar lack of vul¬ 
nerability to white-nose syndrome, but temperature conditions in some western hibemacula are 
thought to be suitable for fungal growth (Siemers and Neubaum, 2015). 
Disturbance from Recreation and Vandalism at Roosts: This species has been character¬ 
ized as intolerant of human activities and quick to abandon roosts that have been disturbed 
(Schmidly, 1991); females will move young to alternate roosts if disturbed (Pearson et al., 1952), 
but it is likely that disturbance may negatively affect reproductive success (Pierson and Rainey, 
1998a). Pierson et al. (1991) noted that the species “is so sensitive to human disturbance that sim¬ 
ple entry into a nursery roost can be enough to induce the colony to abandon a site.” In California, 
only four of 54 maternity roosts known to exist in the late 1980s-early 1990s could be deemed 
secure, and none were thought to be capable of persisting into the long-term future without active 
