4 
PROCEEDINGS OF THE CALIFORNIA ACADEMY OF SCIENCES 
Series 4, Volume 65, Supplement I 
these species, but further biological research and field study are needed to resolve the conservation 
status of these taxa. Many species of concern will be found not to warrant listing.. .Others may be 
found to be in greater danger of extinction than some present candidate taxa” (U.S. Fish and 
Wildlife Service, 1996a: 7597). The Category 2 candidate species of bats designated in 1994 thus 
became known informally as “Bat Species of Concern”. Many of these species of bats were at that 
time or later also categorized as sensitive species by other state and federal land management agen¬ 
cies and conservation organizations, as encouraged by the U.S. Fish and Wildlife Service (1996b). 
Our objectives in this report are to summarize the current conservation status of these former Cat¬ 
egory 2 candidate species of bats and to summarize pertinent biological information on these taxa, 
particularly information that has become available due to research in the ensuing two decades since 
1996. 
Changes in the Federal Status of Bats in the 
United States and Territories 
During the ensuing two decades (1967-1988) since placing the Indiana bat on the list of U.S. 
endangered species, eight additional species or subspecies of bats were designated as endangered 
(Table 2). This includes the categorization of the Guam population of the Mariana fruit bat ( Ptero- 
pus mariannus mariannus) as endangered in 1984 (U.S. Fish and Wildlife Service, 1984), a popu¬ 
lation and taxon subsequently downlisted as threatened together with the population in the Com¬ 
monwealth of the Northern Mariana Islands in 2005 (U.S. Fish and Wildlife Service, 2005). No 
other taxa of bats were added to the list of endangered or threatened species in the U.S. and terri¬ 
tories for the 25 years following 1988, but this changed during 2013-2016 when another four taxa 
were added (Table 2). The Florida bonneted bat ( Eumops floridanus; elevated to full species taxo¬ 
nomic status by Ti mm and Genoways [2004] since the 1994 designation as a Category 1 candidate 
subspecies) was listed as endangered due to multiple factors: habitat loss, habitat degradation and 
modification, as well as threats due to small population size, restricted range, few colonies, low 
fecundity, and relative isolation (U.S. Fish and Wildlife Service, 2013a). The Mariana subspecies 
of the Pacific sheath-tailed bat ( Emballonura semicaudata rotensis ) was listed as endangered in 
2015, in part because several updated studies (for example, Gorresen et al., 2009; Wiles et 
al., 2011; Valdez et al., 2011; Oyler-McCance et al., 2013) confirmed its need for strict protection 
due to: reduction from a larger, multi-island distribution to its present occurrence only on the tiny 
island of Aguiguan; an apparent specialization for native limestone forest as foraging habitat, loss 
of which has been due to over-utilization by feral goats and encroachment by exotic vegetation; 
and risk of future declines due to typhoons and predation (U.S. Fish and Wildlife Service, 2015a). 
The northern long-eared bat was listed as threatened in 2015 (Table 2) due to very recent and dra¬ 
matic population declines caused by the fungal disease white-nose syndrome (U.S. Fish and 
Wildlife Service, 2015b). In 2016, the South Pacific subspecies of the Pacific sheath-tailed bat 
(Emballonura semicaudata semicaudata) also was designated as endangered on American Samoa 
as well as on Fiji, Samoa, Tonga, and Vanuatu. Reasons for endangerment included habitat loss 
from deforestation, mortality from non-native predators, disturbance of caves used as roosts, low 
numbers, vulnerability to catastrophic events, and breakdown of the metapopulation structure due 
to increasing isolation of subpopulations (U.S. Fish and Wildlife Service, 2016). Twenty former 
Category 2 candidate taxa remained among the original 24 species and subspecies of concern given 
these changes (two western subspecies of Townsend’s big-eared bat [Table 1] considered as a sin¬ 
gle species here, coupled with the recognition of the Commonwealth of the Northern Mariana 
Islands and Guam population of the Mariana fruit bat as threatened, the lack of evidence for the 
