Animal Fact Sheet:  Greater Mastiff Bat

Identifying Features

The greater mastiff bat (Eumops perotis) is the largest bat in the United States. They can be easily identified by their very large ears which extend out over its nose. It has short brown to gray-brown fur on its back and paler fur on its underside. Their wings are long and narrow.



These bats do not migrate or hibernate. They remain active year-round.


Ideal habitat for this bat must have large open area with roost sites having vertical faces. They will roost in small colonies in rock fissures in high cliff faces. Because of their large size, they need at least 20 feet of vertical drop from their roosts to gain enough speed for flight. If they end up on the ground, they have to climb up a vertical surface in order to gain enough height to launch into flight.


These bats are found from central California into most of Arizona and some areas of Texas and New Mexico and into Mexico. The southern portion of their range extends to Argentina.

Wild Status

Currently these bats are considered a species of least concern and have federal special status. Bat Conservation International however does consider this bat to be Threatened and Endangered due to no longer being found in many of its previously occupied areas.


They are insectivorous, and although moths are probably their food of choice, any night-flying insect is game.


Typical bat predators include birds of prey such as hawks, falcons and owls.


Mating occurs in the spring. Usually one, but on occasion two pups are born sometime between May and September.

Life Span

It is estimated that their life span is 10-15 years in the wild.


Its wingspan is 20-23 in (50-58cm) and it weighs about 2.0-2.5 oz (56-70 g)..

Extra Fun-facts

  • This bat is also known as the Greater Bonneted Bat.
  • Male mastiff bats have a dermal (skin) glad that becomes enlarged during mating season. It produces a strong odor that is thought to attract females.
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