The greater mastiff bat Eumops perotis (chiroptera: Molossidae) in Oklahoma.
On 17 November 2010, an adult male E. perotis was submitted to the Oklahoma State Department of Health for rabies testing and it tested positive. The bat was found by a home owner within Krebs, Pittsburg County, Oklahoma (34[degrees]55'31.97N, 95[degrees]42'56.86"W). The bat had fallen from a 4-6 m pine tree (Pinus) and was struggling to get airborne from the ground. This seemingly explains the erratic flopping around on the ground reported by the home owner. When on the ground, this long-winged species usually tries to climb a vertical surface to gain enough height (usually ca. 2 m) to launch itself and fly (Vaughan, 1959; Hoffmeister, 1986). The specimen was obtained by the university of Central Oklahoma from the Oklahoma State Department of Health in May 2011 and is deposited in the Natural History Museum (UCONHM 5527) as a fluid-preserved specimen.
The greater mastiff bat is the largest bat in the united States (Best et al., 1996). External measurements (in mm) of the specimen from Oklahoma were: total length, 175; length of tail, 61; length of foot, 16; length of ear, 42; length of forearm, 82; and length of tragus, 6. These measurements are within the range of variation listed by Best et al. (1996) for other adult E. perotis. The tragus is large, broad, and square. Mass was not recorded before the brain was removed for rabies testing. Testes were 6 mm in length. The dermal gular gland was large (7 mm), elevated above the surface of the skin, open, and empty. The ears were united across the top of the head and when laid forward extended ca. 9-10 mm beyond the tip of the nose.
In other parts of its range, E. perotis exhibits year-long nocturnal activity and may enter daily torpor during December-February, decreasing foraging activity when temperatures are <5[degrees]C (Best et al., 1996). Examination of stomach contents of the specimen from Oklahoma revealed portions of antennae, scales, and parts of heads of lepidopterans, and other insects suggesting that the bat had been actively foraging. Previous reports of stomach contents for this insectivorous bat included similar items: crickets, beetles, moths, and other soft-bodied invertebrates (Vaughan, 1959; Ross, 1961).
Typical roosting sites for E. perotis are tall rocky cliffs with crevices (Cockrum, 1960; Best et al., 1996). The species also may seek refuge in buildings in urban settings (Krutzsch, 1955; Cockrum, 1960; Galera et al., 2008). The specimens from Midland, Texas (T. M. Tipps et al., in litt.), and Oklahoma were in urban areas. The specimen from Krebs, Oklahoma, was ca. 725 km northeast of the record in Midland, Texas (T. M. Tipps et al., in litt.), which was a northeastward extension of geographic range by ca. 300 km. Thus, the E. perotis from Oklahoma was ca. 1,000 km northeast of the nearest reported areas of occurrence in the Trans Pecos and Big Bend regions of Texas.
Several explanations are possible to account for E. perotis in Oklahoma. Genoways et al. (2000) proposed that what often has been termed extralimital records of Mexican free-tailed bats (Tadarida brasiliensis) could be explained by individuals that were in pioneering or exploring zones at the margins of their geographic range. Instead of representing accidental or malfunctioning individuals, these bats were exhibiting adaptive behaviors for the species on the dynamic edge of their current range. According to Genoways et al. (2000), bats in the pioneering zone would represent individuals that were in a potentially favorable environmental area that could support the species and its reproductive activities, whereas the exploring zone is an area where only a limited number of individuals of the species might occur. These individuals could be foraging and exploring for habitats that might be appropriate for colonization, but no reproduction is occurring there. Of these two, the E. perotis from Oklahoma might have been an individual in an exploring zone for the species. Arguments against the above are that this species has been described as non-migratory (Cockrum, 1960; Allen, 1987) and that it was disoriented due to rabies. Because more bats are being submitted for rabies testing, reports of rabid E. perotis are more frequent (Constantine, 1979a, 1979b; Galera et al., 2008). The extent to which rabies affects dispersal of bats is neither understood nor documented. There are reported incidences of T. brasiliensis being refractive to rabies and showing no evidence of being adversely affected by rabies, yet testing positive for the virus in the brain and saliva (Burns et al., 1955). Bats can have lethal or nonlethal (viral-neutralizing antibodies) infections of rabies (George et al., 2011). If this E. perotis from Oklahoma had a nonlethal case of rabies, or if it was in an early stage of infection, the bat could have been functioning in a normal way and dispersal to Oklahoma might not represent aberrant malfunctional behavior. Colonies of E. perotis usually are small ([less than or equal to] 100) and often are difficult to locate (Schmidly, 1994). It is possible that this was just one of several bats that had migrated to the area as pioneers or explorers.
The possibility also exists that change in climate (global warming) might be modifying geographic distributions of bats. If gradual warming is occurring in the southwestern united States, occurrences of species usually found farther south but now in northern Texas and Oklahoma might be pioneers-explorers along a dynamic distributional boundary. Another possible explanation for this species in Oklahoma might be translocation by natural or anthropogenic means. These include being blown by winds into a new area, arriving in shipping containers on vehicles, and releases by the public of bats captured elsewhere (Constantine, 2003). It is feasible that because this species is reported to feed at altitudes [less than or equal to] 609 m and over wide areas (M. S. Siders, http://www.wbwg.org), it might have been caught up and accidently dispersed in strong winds.
It is important that biologists continue to identify bats submitted for rabies testing and seek ways to have access to those bats being removed by exterminators. These identifications could provide important information about distributional patterns of bats.
Submitted 18 October 2011. Accepted 14 July 2012. Associate Editor was Troy A. Ladine.
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William Caire * and Lynda Loucks
Department of Biology, University of Central Oklahoma, Edmond, OK 73034 * Correspondent: firstname.lastname@example.org
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|Author:||Caire, William; Loucks, Lynda|
|Date:||Mar 1, 2013|
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