Occasional Papers Museum of Texas Tech University Number 360 17 January 2019
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Occasional Papers Museum of Texas Tech University Number 360 17 January 2019 FIELD IDENTIFICATION KEY AND GUIDE FOR BATS OF THE UNITED STATES OF AMERICA CLINT N. MORGAN, LOREN K. AMMERMAN, KRYSTA D. DEMERE, JEFFREY B. DOTY, YOSHINORI J. NAKAZAWA, AND MATTHEW R. MAULDIN ABSTRACT Bats are the second most speciose lineage of mammals with more than 1,300 recognized species. Overall, bats are extremely ecologically and morphologically diverse, making them of interest to a wide variety of biologists. Bats are also known reservoirs for an assortment of zoonotic diseases, including rabies, for which they are commonly tested if identified as sick, behaving abnormally, or in instances where there has been a significant human exposure. In these cases, proper identification of bat species is important to public health experts as it will inform future testing procedures and management practices, as well as broaden our understand- ing of rabies virus bat variant distributions and disease ecology. Despite the multiple disciplines interested in bats, no key has been developed which includes all species found within the United States. For this reason, a dichotomous key and bat identification guide, designed to differentiate bats to species level, has been developed. This document can be used by people with a variety of backgrounds to morphologically identify bats quickly and accurately using only a scale, a ruler, and attention to detail. Key words: bat guide, bat key, bats, Chiroptera, identification key, public health, rabies virus INTRODUCTION There are 51 species of bats currently documented measurements, range maps, and additional information in the United States (Reid 2006; Baird et al. 2017). that can be utilized when identifying bats in the United Some of these species are widespread in their distribu- States to species level. Researchers from multiple tion and are recorded from the east to the west coast, universities, state agencies and organizations have while other species are restricted in their range and are compiled excellent field guides for specific regions and recorded from only one or a handful of states. Four states, many of which were utilized for the creation of species have been recorded as “accidental” (occurring this document (Menzel et al. 2002; Gannon et al. 2005; rarely, with few records, suggesting no permanent or Reid 2006; Harvey et al. 2011; Ammerman et al. 2012; seasonal populations) in the southern Florida Keys. Schmidly and Bradley 2016). However, an updated, This document contains species descriptions, physical inclusive key to the bats of the entire U.S. has not been 2 OCCASIONAL PAPERS, MUSEUM OF TEXAS TECH UNIVERSITY created nor made available to the public. The primary tory. Additional resources should be consulted for more objective of this project was to create an easily acces- detailed figures, range maps, and both ecological and sible bat identification key that could serve as a resource natural history information that can be valuable when for public health laboratories and could also be utilized identifying bats (see the additional resources section by wildlife rescuers, bat rehabilitation organizations, at the end of the document). biological contractors, and wildlife biologists. Herein, we provide a diagnostic key to the bat species within Bats (order Chiroptera) are a very diverse group the U.S. and emphasize the bat species most commonly of mammals both ecologically and morphologically. submitted to health labs for rabies diagnostics (shown Although there exists a great deal of morphological in bold within the Bat Identification Guide section). We variation within this order, the basic anatomy of bats recommended that the “Key to the Bats of the United is relatively similar. For this reason, it is important to States” should be utilized first to identify the species, understand the general anatomy of a bat and the cor- and then the “Bat Identification Guide” should be used responding terms (Fig. 1) before attempting to identify to corroborate the resulting species’ geographic distri- the species to which a specimen could belong. It is bution, distinguishing characteristics, and measure- worth noting that a single anatomical feature may ments to further validate the identification. have multiple corresponding names. For example, the interfemoral membrane shown in Fig. 1 is also referred This bat key and guide are intended to be used as to as the tail membrane or the uropatagium, as it will a reference to aid accurate and efficient identification be referred to herein. of bat species within the U.S., and therefore, does not attempt to provide any additional information regarding Variations in specific anatomical features, such species-specific ecological information or natural his- as the shape of the uropatagium, full length of tail, or Figure 1. The general anatomy of a bat. MORGAN ET AL.—FIELD KEY FOR BATS OF THE UNITED STATES 3 the length of tail that extends past the uropatagium, should be taken from the “0” mark and not the end of the can be used to distinguish between certain groups ruler. This will allow for more accurate measurements. of bats. Being able to identify the major differences Cutting the tip of the ruler so that the “0” mark is the between families of bats will quickly help to narrow edge is very helpful, especially when measuring ear the list of potential species. Another necessary piece length. When measuring mass (weight), attempt to dry of information is the geographic location where the the bat off before weighing if the specimen is wet, and bat was collected. In addition to those provided in this be sure to measure mass prior to any sample collection. document, distribution maps for many bat species are available through a variety of publications and online Measurements provided herein were compiled resources (see Appendix for additional resources). It from Jacobs (1996), Reid (2006), Ammerman et al. is important to note that these distribution maps are not (2012), and Ceballos (2014) for adult specimens. Ju- geographically immutable boundaries, but can be very veniles of a given species may not be easily identified helpful in determining if a species is likely to occur in by measurements alone; however, young of the year a given locality. Generally, the more closely related are often considered subadults by the time they begin two species of bats are, the more likely they are to be taking flight, and could reach adult size by September similar in their morphology. In these instances, small or October of the same year. If an ‘X’ is given for a details, such as the place where the plagiopatagium con- measurement, that measurement was not provided in nects to the hind limb, or whether the calcar is keeled the reference. If a ‘0’ is given in the place of the tail or un-keeled, could be the only morphological means measurement, the bat has no tail. Measurements from of distinguishing between the two species (when us- Jacobs (1996), Reid (2006), or Ceballos (2014) are ing external characteristics). This scenario is common given as ranges and measurements from Ammerman between some species of Myotis (Fig. 2). et al. (2012) are provided as averages (≈). Measure- ments are taken in millimeters (mm) and indicated as Measuring a specimen is recommended to support follows: HB = head and body length (excluding tail); the putative species identification, and occasionally T = tail length (base to tip of tail); HF = hindfoot length such measurements are the only way to morphologi- (ankle to tip of claw); E = ear length (intertragic notch cally support a species level identification. Commonly to tip of out-stretched ear); M = mass in grams (g); FA reported measurements include total body length, tail = forearm length (from outer edge of elbow to wrist). length, ear length, hindfoot length, and forearm length (Fig. 3). These measurements are best taken by using Species distribution maps were created from calipers or metric rulers. If using a ruler, measurements spatial data provided by the International Union for d c a b Figure 2. Illustration of anatomical traits associated with the hind limb in various species of Myotis. The plagiopatagium of M. grisescens attaches to the tarsus (a), whereas that of M. lucifugus (and others) attaches to the foot at the base of the toes (b). A keeled calcar (c) is present in both M. sodalis and M. leibii, whereas the calcar of M. lucifugus and M. austroriparius is unkeeled (d). 4 OCCASIONAL PAPERS, MUSEUM OF TEXAS TECH UNIVERSITY Figure 3. Typical measurements taken in millimeters. TL = total length, HB = head and body length, T = tail length, TR = tragus, E = ear, HF = hind foot, and FA = forearm. Juveniles (JV) and adults (A) can be distinguished based on amount of epiphyseal-diaphyseal fusion (inset figure). Conservation of Nature (IUCN) Red List (IUCN 2010). suggested that researchers consult additional resources The distributions provided are rough estimates, as inci- to determine more precise geographic distributions of dental occurrences of bat species are relatively common species in question, especially if the collection locality in areas outside of their normal range (particularly mi- is near the edge of a provided distribution. gratory species). For this reason, as well as the ability of climate change to modify animal distributions, it is MORGAN ET AL.—FIELD KEY FOR BATS OF THE UNITED STATES 5 KEY TO BATS OF THE UNITED STATES This key includes the bat species that are com- migrants, with the exception of Diphylla ecuadata monly distributed within the borders of the United (Hairy-legged Vampire Bat) and Desmodus rotundus States of America including Alaska and Hawaii, but (Common Vampire Bat), which were included due to excluding U.S. territories. Geographical information their epizootiological importance. Although the acci- appears in italicized text. For identification help with dental species in the Florida Keys were not included in bats in Puerto Rico, see Gannon et al.