Hawaiian hoary bat

The Hawaiian hoary bat is a medium-sized vesper bat with a wingspan of about 10.5 inches and a body length of 5 to 6 inches. Its fur is dark brown to black, tipped with white or silver, giving a hoary (frosted) appearance. The subspecies semotus is smaller than the mainland hoary bat (L. cinereus) and has a more reddish tint. Genetic studies indicate that the Hawaiian population diverged from North American hoary bats relatively recently, likely via long-distance dispersal across the Pacific.¹

The bat occurs on all main Hawaiian Islands, from sea level to elevations above 2,300 meters. It roosts in native and non-native trees, such as kiawe, coconut palms, and eucalyptus, often hanging from foliage. Foraging typically occurs over open areas, including grasslands, agricultural fields, and near water. The species is migratory in some parts of its range, but Hawaiian populations appear to be resident, with some seasonal movements between islands.

Hawaiian hoary bats are solitary and nocturnal, emerging at dusk to hunt insects, including moths, beetles, and mosquitoes. They use echolocation to navigate and capture prey, with calls that are audible to humans as low-frequency clicks. Mating occurs in the fall, and females give birth to twins in June or July. The bats are known to use torpor to conserve energy during cool periods, a behavior that is unusual for tropical bats.²

Listed as endangered since 1970, the Hawaiian hoary bat faces threats from habitat loss, predation by introduced species such as rats and barn owls, and collisions with wind turbines. The U.S. Fish and Wildlife Service designated critical habitat in 2019, covering over 275,000 acres across the islands. Conservation efforts include habitat restoration, public education, and monitoring of wind energy facilities to reduce bat fatalities.³

One of the least-known aspects is the bat's role in Hawaiian culture and mythology, where it is sometimes referred to as ʻōpeʻapeʻa, meaning 'half-leaf', due to its wing shape. The bat is also notable for its ability to fly in strong winds and rain, which is unusual for bats. Recent research using acoustic monitoring has revealed that the bat's echolocation calls vary by island, suggesting possible local dialects. Additionally, the bat is one of the few mammals that has colonized Hawaii without human assistance, making it a key species for studying island biogeography.

Echolocation

A biological sonar used by bats to navigate and locate prey by emitting high-frequency sounds and listening to echoes.

Endemic

Native to a specific region and found nowhere else.

Torpor

A state of decreased physiological activity, characterized by reduced body temperature and metabolic rate, used to conserve energy.