Perception Channels: tactile ; chemical
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
This species sometimes roosts in high buildings or tunnels where it can be an unsightly nuisance.
Western mastiff bats feed on various insects and may play a role in controlling their populations, hence decreasing losses to agricultural products upon which these insects feed.
Positive Impacts: controls pest population
Eumops perotis is an insectivore feeding primarily on flying insects.
Western mastiff bats feed primarily on insects which they catch in flight. These bats rarely utilize night roosts and feed at night, with foraging ranges exceeding 24 km from roost sites, and a long foraging period of 6 to 7 hours. Prey includes relatively small, low-flying, and weak-flying insects. They usually feed from ground to tree-level but may soar to heights of some 60 m in rugged terrain. It is interesting to note that flightless insects, including ants and crickets, comprise part of their diet even though these bats are unable to take off from the ground, requiring that the prey be snatched up as the bat flies by. These prey items are likely to be taken from surfaces such as canyon walls (Cockrum 1960; Texas Tech, 1997; Ahlborn, 2000).
Some insect prey include: moths, crickets, grasshoppers, bees, dragonflies, leafbugs, beetles, true bugs, ants and wasps.
Animal Foods: insects
Primary Diet: carnivore (Insectivore )
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 )
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
Eumops perotis is easily identified by large ears united across the top of its skull and projecting about 10 mm beyond its snout. It is the largest molossid in North America. Characteristic to the family Molossidae, its wings are distinctively long but rather narrow. Their flight membranes are tough and leathery. This is a free-tailed bat whith relatively large feet. Its pelage is short, velvety, and whitish at the roots. Coloration is dark to greyish brown dorsally and more pale ventrally. The dental formula is I 1/2, C 1/1, P 2/2, M 3/3 X 2 = 30. Both sexes of the western mastiff bat possess a peculiar dermal gland on the throat which looks like a pouch and produces an odoriferous secretion, athough this gland is much more developed in the males (Ahlborn, 2000; Texas Tech, 1997; Allen, 1987).
Average mass: 57 g.
Average length: 81 mm.
Range wingspan: 0.53 to 0.60 m.
Average wingspan: 0.56 m.
Other Physical Features: endothermic ; bilateral symmetry
Males attract females with secretions from their enlarged dermal gland during the mating season.
Mating System: polygynous
Males and females of this species remain together throughout the year, including the period when young are produced. Mating occurs in early spring when the dermal gland of adult males is most functional and the testes enlarge and descend. Normally only one young is produced per pregnancy, with twins being very rare. Eumops perotis is a eutherian with a gestation period of approximately 80 to 90 days. The offspring are dull black in color at birth and are naked, except for tactile hairs on the feet and face. The period of parturition usually extends from June into July, varying more than for any other bat in the United States. A nursery colony of these bats may contain young ranging from newborn individuals to ones already several weeks old. Nursery roosts are located in tight rock crevices or holes in buildings at least 90 cm deep and 5 cm wide (Texas Tech, 1997; Ahlborn, 2000).
Breeding season: March to July
Range number of offspring: 1 to 2.
Average number of offspring: 1.
Range gestation period: 80 to 90 days.
Range weaning age: 1 to 2 months.
Key Reproductive Features: gonochoric/gonochoristic/dioecious (sexes separate); sexual ; fertilization (Internal ); viviparous
Males remain with females during the period when young are produced but it is uncertain what degree of assistance in care they actually provide.
Parental Investment: pre-fertilization (Provisioning, Protecting: Female); pre-hatching/birth (Provisioning: Female, Protecting: Female); pre-weaning/fledging (Provisioning: Female, Protecting: Female); pre-independence (Provisioning: Female, Protecting: Female)
The western mastiff bat (Eumops perotis), also known as the western bonneted bat, the greater mastiff bat, or the greater bonneted bat, is a member of the free-tailed bat family, Molossidae. It is found in the Western United States, Mexico and South America. This species is the largest bat native to North America, and some of its distinguishing characteristics are its large ears, wings, and forearms.[2][3] The subspecies Eumops perotis californicus is a species of concern as identified by the U.S. Fish and Wildlife Service. The range of this subspecies is principally southwest desert regions of the United States, along the border with Mexico; however, the range extends as far north on the Pacific coast as Alameda County, California.[4]
The western mastiff bat is located in both South America and North America. In South America, the species is found in Brazil and its neighboring countries, ranging southward to northern Argentina. It can also be found in Cuba.[5] The subspecies in North America, Eumops perotis californicus, resides in the southwestern United States (California, Arizona, New Mexico, Texas) and ranges southward to parts of central Mexico.[6]
The greater mastiff bat prefers to live in habitats with open space. Some examples include desert scrub, woodlands, and grasslands.[7] Roosts are commonly located in crevices of rocky areas, such as cliffs and canyons,[6] and have also been found within man-made structures such as buildings and tunnels.[7] As the western mastiff bat cannot take off from flat surfaces, these spots are at least 3 meters above ground, providing the bat with sufficient space to drop from and take flight.[6]
Eumops perotis is most notable for its size, as it is the largest North American bat. It has a body length of 6.2 to 7.2 in (16 to 18 cm)[8] and a wingspan of over 22 in (56 cm).[5] The body mass of this species can range from 60 to 70 g (2.1 to 2.5 oz).[8] The wings are long yet narrow, which limits the species' maneuverability in the air. The body mass of this species can range from 45 to 73 g (1.6 to 2.6 oz).[8] A defining characteristic is its large ears that range between 1.4 to 1.85 in (3.6 to 4.7 cm) and extend over the bat's snout. It also has large forearms with a length of 2.9 to 3.3 in (7.4 to 8.4 cm).[8] Males are larger than females and also have an odoriferous gland on their throat, which is less developed in females.[9] The western mastiff bat is mostly dark in color, as the body is primarily brown or gray, though the underside is a lighter color.[8]
Western mastiff bats are nocturnal, leaving roosts at night to find food.[6] Unlike most North American bats, they do not undergo either migration or prolonged hibernation, but are periodically active all winter.[2] The size of colonies varies, but they usually consist of less than 100 bats. Males and females live together yearly, even during maternity periods.[2]
The species is very active at night, spending 6–7 hours flying a night for a total distance of about 14.9 miles (24.0 km).[3] Its long, narrow wings allow the bat to maintain flight at high speeds for long periods of time. These bats can reach heights of 196 feet (60 m), though they are also observed flying closer to the ground.[9] One notable characteristic of this species is its high pitched echolocation call, as it can be heard from heights of 990 feet (300 m).[6]
The western mastiff bat mainly feeds on small insects. Moths are its biggest food source, but it has been observed to eat beetles, ants, dragonflies, crickets, and grasshoppers.[5][9]
This species begins mating in early spring and the offspring is born in the summer, usually by July.[9] The gestation period is about 80–90 days, and females give birth to one offspring at a time, though twins are possible.[9] The parturition period varies greatly. The young remain in a nursery after birth, with both the males and females.[9]
Though the western mastiff bat is listed under the Least Concern Category by the IUCN Red List of Threatened Species, Bat Conservation International reports that its numbers are decreasing in certain areas. One reason for its decline is its inability to find suitable water sites for drinking, as its size prevents it from drinking from small bodies of water.[10] Grazing and the use of pesticides have impacted foraging habitats.[2] The loss of cliff sites as a result of urban/suburban development and activities such as water impoundments, highway building, and quarry operations has also contributed to the species' endangered status, making it harder to find adequate roost places.[2]
The western mastiff bat (Eumops perotis), also known as the western bonneted bat, the greater mastiff bat, or the greater bonneted bat, is a member of the free-tailed bat family, Molossidae. It is found in the Western United States, Mexico and South America. This species is the largest bat native to North America, and some of its distinguishing characteristics are its large ears, wings, and forearms. The subspecies Eumops perotis californicus is a species of concern as identified by the U.S. Fish and Wildlife Service. The range of this subspecies is principally southwest desert regions of the United States, along the border with Mexico; however, the range extends as far north on the Pacific coast as Alameda County, California.
