O’SHEA, CRYAN & BOGAN: UNITED STATES BAT SPECIES OF CONCERN 
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aries (for example, the northern edge of the distribution of the Arizona myotis occurs in southern 
Colorado, but it is not assigned special status in that state); some species are given special status 
by states at the edges of their distribution (where they may tend to be rare) but not by some states 
at the core of the range (for example, the long-legged myotis). States with greater diversity of bats 
tend to have greater numbers of species of bats with special status designations (for example, 
Arizona, California, and Texas), and those states with lower diversity of bats may have just a sin¬ 
gle special status species (for example, Maine, Delaware, Massachusetts). 
Description, Distribution and Systematics. — Most of the species of concern are rela¬ 
tively distinctive in appearance, but a few are more difficult to discriminate and require some 
expertise. Less-experienced readers should consult local experts in mammalogy for assistance, and 
in cases where identification may be in doubt, collection of a few voucher specimens is advisable. 
Difficulties in identification mostly apply to species of Myotis. In some areas, even experts must 
take care in differentiating Yuma myotis ( M . yumanensis) from little brown myotis (M lucifugus ), 
or western small-footed myotis (M. ciliolabrum ) from California myotis (M. californicus; see 
species accounts for details). Distributions of species are fairly well-defined in broadest outlines, 
but within those outlines local and regional occurrences can be poorly known, and new locality 
records continue to be accrued for species of concern. New basic surveys of bat faunas of areas 
under various management jurisdictions can yield such information. New state records (for exam¬ 
ple, Adams and Lambeth, 2015) and more anomalous locality records of likely wandering individ¬ 
uals (for example, Caire and Loucks, 2013) continue to be documented. Distributions of species 
are not static. For example, interesting changes in distribution of the species of concern are likely 
to occur over time with climate change. 
Refinements in knowledge of species taxonomy also are likely to occur. Although the nomen¬ 
clature of most species of concern appears fairly stable, future changes can be expected given new 
insights that may be provided through advances in molecular techniques and quantitative system¬ 
atic analyses. Multiple examples of changes in understanding of taxonomy within the bat fauna of 
the U.S. within the past 35 years suggest that more will occur in the future. As examples, names of 
the following U.S. species of concern all had been changed since 1981: Corynorhinus rafinesquii, 
Corynorhinus townsendii, Idionycteris phyllotis, Myotis ciliolabrum, and Nyctinomops macrotis. 
The validity of sub-specific designations and nomenclature will likely be subject to change as well 
(for example, Piaggio and Perkins, 2005; Piaggio et al., 2011). 
Habitats and Relative Abundance. — The species of concern vary in both general and 
more specific types of habitats used. Based on literature reviews in the species accounts, we found 
it useful to group each species within general habitat types, with qualitative judgements about more 
specific habitats nested by species within these general habitats (Table 3). These categories are 
qualitative and are largely based on results of disparate mist netting surveys, usually conducted 
without prior design for comparisons among studies. We acknowledge that many factors can influ¬ 
ence the relative abundance and species composition of bat communities and that these factors are 
poorly known in most surveys (see Introduction and Objectives sections). One of these may be sus¬ 
ceptibility to capture in mist nets based on constraints imposed by wing morphology on maneu¬ 
verability and agility. Based on those factors alone, however, results of many surveys are incon¬ 
sistent with predictions. In the western U.S., for example, less-maneuverable species (high wing 
loading and high aspect ratio) such as big free-tailed bats and greater bonneted bats (Norberg and 
Rayner, 1987) are seldom captured in mist nets except where colonies are known or subsequently 
found to be located in nearby cliffs. In other surveys, species that are known to be highly maneu¬ 
verable and which roost in smaller colonies dispersed across the landscape, such as many of the 
vespertilionids, can rank high in abundance. These rankings can be highly variable among surveys, 
best illustrated by the western coniferous forest and woodland species of Myotis (see below). 
