Lasiurus cinereus

Hoary Bat

Family: Vespertilionidae · Class: Mammalia · Order: Chiroptera

Conservation status: G3G4 S4

The hoary bat is North America's most widely distributed bat species and the largest bat found in California. Adults measure 130 to 140 mm (5.1 to 5.5 inches) in total length with a wingspan reaching 350 to 410 mm (13.8 to 16.1 inches). Males typically weigh 20 to 26 grams, while females are larger at 26 to 35 grams. The species derives its common name from the distinctive frosted appearance of its fur, which results from individual hairs being tipped with white or cream coloring over a brown or yellowish-brown base. The dorsal fur appears grizzled or hoary, while the ventral surface is lighter with a prominent yellowish-white throat patch. The ears are short, rounded, and edged with black, and the tail membrane is heavily furred on the dorsal surface. Hoary bats occur throughout California, from sea level to elevations of 3,900 meters (12,800 feet) in the Sierra Nevada. The species ranges across most of North America, from southern Canada to Central America, and is also found in South America and Hawaii. In California, hoary bats are present in all counties and occupy diverse habitats from coastal areas to high mountain regions. They are among the few bat species that migrate long distances, with northern populations traveling south for winter. The species inhabits a wide variety of forested and woodland habitats, showing preference for areas near water sources. Hoary bats roost primarily in foliage of both coniferous and deciduous trees, typically 3 to 5 meters above ground. They select roost sites that provide protection from wind and predators while allowing easy flight access. During migration and winter, individuals may roost in dense vegetation, tree cavities, or occasionally buildings. The species demonstrates extensive ecological adaptability, occurring in riparian forests, oak woodlands, mixed conifer forests, urban parks, and agricultural areas with suitable tree cover. Hoary bats are solitary except during mating and when females are raising young. They emerge late in the evening to forage, typically 1 to 3 hours after sunset. The diet consists primarily of moths, comprising up to 83% of their prey, supplemented by beetles, flies, mosquitoes, and other flying insects. Their large size and strong flight capabilities allow them to capture prey as large as 25 mm in length. Mating occurs during late summer and fall migration, with delayed implantation extending gestation to approximately 90 days. Females give birth to 1 to 4 pups, typically twins, between late May and early July. Pups are capable of flight at 5 to 6 weeks of age. The hoary bat is not federally listed but faces conservation challenges from habitat loss, wind energy development, and pesticide use. The species' Global/State conservation rank of G3G4 S4 indicates it is apparently secure in California but may be vulnerable globally. Wind turbines pose a significant threat during migration periods, with hoary bats comprising a large proportion of bat fatalities at wind energy facilities. Climate change may alter migration patterns and suitable habitat availability. Conservation efforts focus on protecting roosting habitat and implementing measures to reduce wind turbine mortality during peak migration periods.

Data from The California Species Project — 14,000+ California species with verified data from CNPS, CDFW, USFWS, and more.