Western Red Bat (Lasiurus blossevillii)
- Protection Status Notes
- Nothing is known about the status of this bat, since like other foliage-roosting bats, it does not form colonies and is difficult to find. However, it is considered a Species of Special Concern in California, Arizona, and Utah, but not in Texas.
- Lasiurus blossevillii can be distinguished from all other western bat species except Lasiurus borealis (the eastern red bat) by its distinctive red coloration, and can be distinguished from L. borealis by its slightly smaller size and lack of frosted appearance. The only area where these two species are known to overlap is western Texas.
- Life History
- Western red bats mate in late summer or early fall. Females become pregnant in spring and have a pregnancy of 80‑90 days. Females may have litters of up to five pups per year. This species is considered to be highly migratory. Although generally solitary, western red bats appear to migrate in groups and forage in close association with one another in summer. The timing of migration and the summer ranges of males and females seem to be different. Winter behavior of species is poorly understood. The eastern red bat has been found hibernating in leaf‑litter. Arousal from hibernation on warm days to feed has been reported, as has periodic foraging during the winter in the San Francisco Bay area. Predators reported for L. blossevillii include birds (e.g. scrub jays, falcons, accipiters, owls, roadrunners), opossums, and domestic cats.
L. blossevillii is typically solitary, roosting primarily in the foliage of trees or shrubs. Day roosts are commonly in edge habitats adjacent to streams or open fields, in orchards, and sometimes in urban areas. There may be an association with intact riparian habitat (particularly willows, cottonwoods, and sycamores). Roost sites are generally hidden from view from all directions except below; lack obstruction beneath, allowing the bat to drop downward for flight; lack lower perches that would allow visibility by predators; have dark ground cover to minimize solar reflection; have nearby vegetation to reduce wind and dust; and are generally located on the south or southwest side of a tree. L. blossevillii may also occasionally use caves, as both dead and live western red bats, including a pregnant female, have been collected from Carlsbad Caverns in New Mexico.
Western red bats generally begin to forage one to two hours offer sunset. Although some may forage all night, most typically have an initial foraging period corresponding to the early period of nocturnal insect activity, and a minor secondary activity period corresponding to insects that become active several hours before sunrise. Western red bats have been observed feeding around street lights and flood lights. Reported prey items include homopterans, coleopterans, hymenopterans, dipterans, and lepidopterans.
- L. blossevillii has a broad distribution reaching from southern British Columbia in Canada, through much of the western United States, through Mexico and Central America, to Argentina and Chile in South America. In Texas it is known only from the western tip of the Trans Pecos.
- Threats and Reasons for Decline
- Loss of riparian zones, primarily due to agricultural conversion and creation of water storage reservoirs has reduced both small red batroosting and foraging habitat of red bats. The intensive use of pesticides in fruit orchards may constitute a threat to roosting bats and may significant reduce the amount of insect prey available. Controlled burns may be another significant mortality factor for red bats that roost in leaf litter during cool temperatures.
- Ongoing Recovery
- Since the western red bat feeds heavily on moths and often lives in orchards, it is presumed to be highly beneficial to orchardists. Because riparian habitat along streams is one of the most rapidly disappearing in the West, it is possible that this bat has undergone substantial decline due to habitat loss.
- The following areas need more investigation to accurately determine the status of and conserve the red bat in the western U.S.: habitat requirements (especially roost sites and foraging habitat), altitudinal distribution, migration patterns, effects of controlled burns, and effects of pesticide use in orchards.
- Additional details can be found in the online version of The Mammals of Texas for the Western Red Bat