and behavior Western mastiff bats are nocturnal, leaving roosts at night to find food. Unlike most North American bats, they do not undergo either migration or prolonged hibernation, but are periodically active all winter. The size of colonies varies, but they usually consist of less than 100 bats. Males and females live together yearly, even during maternity periods. The species is very active at night, spending 6–7 hours flying a night for a total distance of about . Its long, narrow wings allow the bat to maintain flight at high speeds for long periods of time. These bats can reach heights of , though they are also observed flying closer to the ground. One notable characteristic of this species is its high pitched echolocation call, as it can be heard from heights of . Diet 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. Reproduction This species begins mating in early spring and the offspring is born in the summer, usually by July. The gestation period is about 80–90 days, and females give birth to one offspring at a time, though twins are possible. The parturition period varies greatly. The young remain in a nursery after birth, with both the males and females. Conservation 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. Grazing and the use of pesticides have impacted foraging habitats. 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. References External links Eumops Bats of North America Bats of Central America Bats of South America Bats of Brazil Bats of Mexico Bats of the United States Mammals of Argentina Mammals of Bolivia Mammals of Colombia Mammals of Ecuador Mammals of Paraguay Mammals of Peru Bat, Western Bat, Western Mammals described in 1821