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Noteworthy records of bats from the Trans-Pecos region of Texas. (General Notes).

Recent investigations of bat communities in the Trans-Pecos region of Texas provided noteworthy records for six species (Myotis californicus, Myotis volans, Lasiurus borealis, Nyctinomops femorosaccus, Nyctinomops macrotis and Eumops perotis). All voucher specimens reported herein (skins and skulls), and their associated tissues, are deposited in the Collection of Recent Mammals in the Natural Science Research Laboratory of the Museum of Texas Tech University (TTU).

Myotis californicus.--The California myotis is an established resident of the Trans-Pecos area and has been documented in El Paso, Culberson, Jeff Davis, Presidio and Brewster counties, yet records of this species from Hudspeth County are lacking (Schmidly 1991; Davis & Schmidly 1994). Two females (TTU 82465, 82467) were obtained with mist nets set across a pool of a desert spring on 18 June 2001 at the Indio Mountains Research Station (University of El Paso), Hudspeth County (UTM 13R 498907E 3407109N, elevation 1280m). The edges of the pool were overgrown with cattail (Typha sp.) and a rock ridge bordered the northeast side. The surrounding vegetation consisted of thorny desert scrub, including acacia (Acacia sp.), yucca (Yucca sp.) and prickly pear (Opuntia sp.). The discovery of M. californicus in Hudspeth County completes a contiguous distribution of this species across the western Trans-Pecos region. Associated species of bats encountered at this site on 18 June include Pipistrellus hesperus, Antrozous p allidus, Myotis velifer and Myotis volans.

Myotis volans.--The long-legged myotis is considered relatively rare in Texas, yet it is common in the higher elevations of extreme western Texas. In the Trans-Pecos area, this species has been documented in the mountainous regions of Culberson, Jeff Davis, Presidio and Brewster counties, with an addition record from Knox County in the Rolling Plains (Schmidly 1991; Davis & Schmidly 1994). On 18 June 2001, one female M. volans (TTU 82466) was captured at the Indio Mountains Research Station (locality same as above). The elevation of the capture site (1280m) is atypical of that associated with M. volans in west Texas, as it is usually found between 2000 to 3000m (Warner & Czaplewski 1984). Other bats captured in association with this species on 18 June were M. velifer, M. californicus, P. hesperus and A. pallidus.

Lasiurus borealis.--The eastern red bat displays a spotty distribution in the Trans-Pecos region, where it typically is found in mountainous terrain (Schmidly 1991; Davis & Schmidly 1994). Three pregnant females (TTU 82478, 82479, 82480), each having three embryos with crown rump lengths ranging from 12 to 20mm, were captured in mist nets on 22 May 2001 at Big Bend Ranch State Park (BBRSP), Presidio County (UTM 13R 589266E 3269761N, elevation 1012m). In Presidio County, L. borealis is known from the Chinati Mountains (Schmidly 1991) and the Sierra Vieja (Jones & Bradley 1999). Yancey's (1997) comprehensive survey of the mammals of BBRSP produced no record of L. borealis, yet he listed it as a probable summer migrant of the surrounding riparian woodland habitats.

The capture site was characterized by a dense growth of cottonwoods (Populus sp.) comprising a riparian gallery forest spanning more than three kilometers in length. The site was spring-fed and water levels along this intermittent stream varied little between visits throughout the spring and summer in 2001. This locality is atypical of Chihuahuan Desert habitat, and it likely plays an important role in providing suitable roosting and foraging grounds for bats. The embryos obtained were approaching full-term developmentally, suggesting the adults were to give birth in the area. Forty-one bats were captured with L. borealis on 22 May, including Mormoops megalophylla, M. californicus, P. hesperus, Lasiurus cinereus, A. pallidus and Tadarida brasiliensis.

Nyctinomops femorosaccus.--The distribution of the pocketed free-tailed bat in Texas is quite restricted, and previously has been documented only from Big Bend National Park (BBNP), Brewster County (Easterla 1968; Schmidly 1991; Higginbotham & Ammerman 2002). One lactating female (TTU 82477) was collected in a mist net over a stock tank on 6 July 2001 at BBRSP, Presidio County (UTM 13R 602303E 3258748N, elevation 1300m) in desert scrub habitat dominated by creosote bush (Larrea tridentata). This record expands the known distribution of this species in Texas 80km west of the previously known range and represents the first account for this species from Presidio County. Yancey (1997) reported N. femorosaccus as a likely occurrence in BBRSP, yet he did not encounter any during his extensive survey of the mammals there. During a recent study in nearby Brewster County at BBNP, N. femorosaccus was encountered only in nets stretched over open water with sizeable surface area (Higginbotham & Ammerman 2002). The epheme ral nature of full stock tanks and other sizeable bodies of water at BBRSP may explain the species' absence from past studies in the area. The pocketed free-tailed bat roosts in crevices of high rocky canyons in BBNP (Higginbotham & Ammerman 2002). Deep canyons with suitable crevices are numerous at BBRSP, and it is likely that roosts of N. femorosaccus occur within them. Eptesicus fuscus, T. brasiliensis, Nyctinomops macrotis and Eumops perotis were captured on 6 July in association with this species.

Nyctinomops macrotis.--Reports of the big free-tailed bat from the Trans-Pecos area are scattered sparsely across both upland and lowland habitats in Brewster, Presidio, Jeff Davis, Reeves, Culberson and El Paso counties (Schmidly 1991; Davis & Schmidly 1994). An adult female (TTU 82469) was captured on 1 July 2001 at an upland site within coniferous forest at the Davis Mountains Preserve (The Nature Conservancy of Texas), Jeff Davis County (UTM 13R 584126E 3394303N, elevation 1860m). The rare occurrence of this species in the Davis Mountains uplands is evidenced by systematic studies of mammals in the vicinity since 1998, in which only a single specimen of N. macrotis has been encountered at the Davis Mountains Preserve (Bradley et al. 1999).

Additionally, one pregnant female N. macrotis (TTU 82468; embryo crown-rump length = 27.5mm) was collected on 29 May 2001 at the same locality in BBRSP as the previously reported L. borealis. Eight lactating females (TTU 82469, 82470, 82471, 82472, 82473, 82474, 82475) were taken on 6 July 2001 in mist nets at BBRSP at the same site as the N. femorosaccus discussed above. These two localities represent vastly different habitats within BBRSP. The former was a riparian gallery forest bordering a narrow, intermittent stream, and the latter, a stock tank (surface area 15 by 20m) within desert scrub habitat. A single specimen of N. macrotis was obtained at BBRSP prior to the work reported herein (Yancey 1997).

In Texas, encounters of significant numbers of N. macrotis historically have been documented only from BBNP in Brewster County (Borell & Bryant 1942; Easterla 1973; Higginbotham & Ammerman 2002). However, recent investigations of mammals at the Davis Mountains State Park, Jeff Davis County, have produced several captures of N. macrotis at a lowland site. These accounts suggest that N. macrotis is perhaps more common in the Trans-Pecos region than was thought previously.

Eumops perotis.--Re ports of the western mastiff bat from Texas are few, and all originate from the Trans-Pecos region in proximity to the Rio Grande corridor (Schmidly 1991). This work reports an additional record of one adult male (TTU 82476) collected at BBRSP on 6 July 2001 from the same locality as the aforementioned molossids (N. femorosaccus and N. macrotis). Three reports exist for E. perotis from Presidio County over the past 45 years (Eads et al. 1957; Ohlendorf 1972; Scudday 1976). Scudday (1976) mentions E. perotis as fairly common at Arroyo Segundo (BBRSP), a site also netted by Yancey (1997). This same locality was surveyed several times during summer 2001, yet no western mastiff bats were encountered.

Maneuvering ability is apparently compromised in the western mastiff bat due to its wing morphology and large size (Findley et al. 1971), and therefore it probably avoids smaller bodies of water, or enclosed areas. Eumops perotis is known to roosts in crevices within high canyon walls typical of the rocky, rugged terrain of the Big Bend region, therefore, they may be more common in the area than the historical capture data suggests, yet more difficult to capture where large bodies of water are scarce.

Eumops perotis, N. femorosaccus and N. macrotis were encountered together at a single locality although extensive sampling was conducted throughout BBRSP during this survey and by Yancey (1997). A distinguishing feature of the site where all three species were captured was the size of the tank (15 by 20 in). When nets spanned the center of the tank, 93 % of mist net captures consisted of the four species of molossids known to inhabit the area, including Tadarida brasiliensis. During sampling periods when mist nets were set only along the perimeter of the tank, molossids were not encountered in the nets, although audible echolocation calls associated with both E. perotis and N. macrotis frequently were heard throughout the evening. This suggests that the larger molossid species inhabiting the Trans-Pecos region of Texas are obligates of large, open water sources for drinking. Therefore, the rarity with which these bats are encountered in the Trans-Pecos area may be explained in part by the significant fluctuat ion in surface area of sizeable, reliable water sources in the region. Consequently, the adjacent Rio Grande is an important resource for these species, as it is a stable source of water relative to other, often ephemeral, sources of water in the region.


The fieldwork and collection of specimens were conducted in accordance with scientific permits issued by the Texas Parks and Wildlife Department (SPR-0790- 189 and 55A-00). Financial assistance was facilitated by research assistantships granted to J. L. Higginbotham, R. S. DeBaca and J. G. Brant during the summer of 2001 by the Department of Biological Sciences at Texas Tech University. Access to the Indio Mountains Research Station was provided by J. D. Johnson, University of El Paso. Access and logistic support were provided by the Nature Conservancy of Texas and by the personnel of the Big Bend Ranch State Park (L. Armendariz, Superintendent). M. Revelez, M. A. Abbey, A. Matthews and B. Reece assisted in the collection and preparation of specimens.


Borrell, A. & M. D. Bryant. 1942. Mammals of the Big Bend area of Texas. Univ. California. Publ. in Zool., 48:1-62.

Bradley, R. D., D. S. Carroll, M. L. Clary, C. W. Edwards, I. Tiemann-Boege, M. J. Hamilton, R. A. Van Den Bussche & C. Jones. 1999. Comments on some small mammals from the Big Bend and Trans-Pecos regions of Texas. Occas. Pap. Mus., Texas Tech Univ., 193:1-6.

Davis, W. B. & D. J. Schmidly. 1994, The mammals of Texas. Texas Parks and Wildlife Dept., Austin, Texas, x + 338 pp.

Eads, R. B., J. E. Grimes & A. Conklin. 1957. Additional Texas bat records. J. Mammal., 38:514.

Easterla, D. A. 1968. First records of the pocketed free-tailed bat for Texas. J. Mammal., 49:515-516.

Easterla, D. A. 1973. Ecology of the 18 species of Chiroptera at Big Bend National Park, Texas. Northwest Missouri St. Univ. Stud., 34:1-165.

Findley, J. S, E. H. Studier & D. E. Wilson. 1971. Morphological properties of bat wings. J. Mammal., 53:429-444.

Higginbotham, J. L. & L. K. Ammerman. 2002. Chiropteran community structure and seasonal dynamics in Big Bend National Park, Texas. Spec. Publ. Mus., Texas Tech Univ., 44:1-44.

Jones, C. & R. D. Bradley. 1999. Notes on red bats, Lasiurus (Chiroptera: Vespertilionidae), of the Davis Mountains and vicinity, Texas. Texas J. Sci., (51)4:341-344.

Ohlendorf, H. M. 1972. Observations on a colony of Eumops perotis (Molossidae). Southwestern Nat., 17:297-300.

Schmidly, D. J. 1991. The bats of Texas. Texas A&M Univ. Press, College Station, xvii + 188 pp.

Scudday, J. F. 1976. Vertebrate fauna of the Fresno Canyon area. Pp. 97-110, in Fresno Canyon a natural area survey no 10. Lyndon B. Johnson School of Publ. Aff., The Univ. of Texas at Austin, 144 pp.

Warner, R. M. & N. J. Czaplewski. 1984. Myotis volans. Mammalian Species, 224:1-4.

Yancey, F. D., II. 1997. The mammals of Big Bend Ranch State Park, Texas. Spec. Publ. Mus., Texas Tech Univ., 39:1-210.

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Author:Higginbotham, Jana. L.; DeBaca, Robert S.; Brant, Joel G.; Jones, Clyde
Publication:The Texas Journal of Science
Geographic Code:1U7TX
Date:Aug 1, 2002
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