Western Bonneted Bat description

Differs from EUMOPS UNDERWOODI in a longer forearm (73-83 mm vs. 65-74 mm), longer ears (36-47 mm vs. 28-32 mm), broad square tragus rather than small and rounded, and greatest length of skull greater than 30 mm rather than usually under 30 mm (see Hoffmeister 1986 for further cranial distinctions). Much larger than other similar bats in western North America, where species with a free tail never exceed about 140 mm in total length or 64 mm in forearm length (EUMOPS GLAUCINUS of Florida, West Indies, and southern Mexico reaches 165 mm in total length and 69 mm in forearm length).

Western Bonneted Bat habitats

Habitat and Ecology

The habitat consists of extensive open areas with potential roost sites having vertical faces to drop off from and take flight, such as crevices in rock outcroppings and cliff faces, tunnels and tall buildings. This species inhabits various types of open, semi-arid to arid habitats (Cockrum 1960, Allen 1987, Best et al. 1996,Ahlborn 2000). Itis an insectivore (Barquez et al. 1993).

  • Terrestrial

Suitable habitat for the western mastiff bat consists of extensive open areas with potential roost locations having vertical faces to drop off from and take flight, such as crevices in rock outcropings and cliff faces, tunnels and tall buildings. This species inhabits various types of open, semi-arid to arid habitats. These include coastal and desert scrublands, annual and perennial grasslands, conifer and deciduous woodlands, as well as palm oases (Ahlborn, 2000; Cockrum, 1960; Allen, 1987).

Range elevation: 5 to 300 m.

Habitat Regions: terrestrial

Terrestrial Biomes: desert or dune ; chaparral ; forest ; scrub forest

Other Habitat Features: urban ; suburban

Comments: North America: arid and semiarid, rocky canyon country habitats in the Chihuahuan Desert; roosts in crevices and shallow caves on the sides of cliffs and rock walls, and occasionally buildings. Roosts usually high above ground with unobstructed approach. Most roosts are not used throughout the year. May alternate between different day roosts.

Western Bonneted Bat size

Length: 19 cm

Weight: 65 grams

Sexual Dimorphism: Males are larger than females.

Average: 175 mm
Range: 159-187 mm

Range: 45.5-73 g

Western Bonneted Bat distributions

This species occurs from California to Texas (USA), south to Zacatecas and Hidalgo (Mexico), in western Peru, Bolivia, northern Argentina, Paraguay, Brazil and Cuba (Simmons 2005). The distribution includes Misiones in Argentina and all of Paraguay and exclude southern tip of distribution in Argentina (Barquez et al. 2006). The Cuban material may be misidentified (Mancina pers. comm.). It also includes south Colombia.

The distribution of the western mastiff bat is patchy. It can be found from the coast of the southwestern United States into central Mexico and southeast to Cuba. The northern limit of its range is the southern half of California. In the United States it extends southeast into western Texas through southern Nevada and southwestern Arizona. The southern limit of its range is in Argentina. This species is non-migratory (Hall, 1981, Allen, 1987, Cockrum, 1960).

Biogeographic Regions: nearctic (Native ); neotropical (Native )

occurs (regularly, as a native taxon) in multiple nations

Western Bonneted Bat Conservation Status

Red List Category
Least Concern

Red List Criteria


Year Assessed

Barquez, R. & Diaz, M.

Solari, S.


This species is listed as Least Concern in view of its wide distribution, presumed large population, and because it is unlikely to be declining at nearly the rate required to qualify for listing in a threatened category.

  • 2008
    Least Concern (LC)
  • 1996
    Lower Risk/least concern (LR/lc)

Apparently, litte data is available for the current status of this bat species. Bat Conservation International lists Eumops perotis on its Threatened and Endangered Bats List due to the the fact that it uses only select drinking sites and is severely limited by the availability of drinking water. Because its wing structure is adapted for fast and straight-line flight, it is unable to drink from water sources less than 30 m long. As a consequence, western mastiff bats are no longer found in many previously occupied areas and populations may be in decline (Acker, 2001).

Temperate North American bats are now threatened by a fungal disease called “white-nose syndrome.” This disease has devastated eastern North American bat populations at hibernation sites since 2007. The fungus, Geomyces destructans, grows best in cold, humid conditions that are typical of many bat hibernacula. The fungus grows on, and in some cases invades, the bodies of hibernating bats and seems to result in disturbance from hibernation, causing a debilitating loss of important metabolic resources and mass deaths. Mortality rates at some hibernation sites have been as high as 90%. While there are currently no reports of Eumops perotis mortalities as a result of white-nose syndrome, the disease continues to expand its range in North America.

US Migratory Bird Act: no special status

US Federal List: no special status

CITES: no special status

IUCN Red List of Threatened Species: least concern

United States

Rounded National Status Rank: N3 - Vulnerable

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