Lasiurus borealis
red bat

Lasiurus borealis, or red bats, are widely distributed in forested regions, occurring from southern Canada through Central America and into Chile and Argentina. Red bats migrate to warmer regions during winter.

Lasiurus borealis are fast flying bats that live throughout the Americas. They tend to choose habitats that are sparsely to moderately populated by humans and are rare in heavily urbanized areas.

Red bats are medium sized bats having a total length of 93 to 117 mm. Body length is approximately 40 to 50 mm and weight ranges between 7 to 13 g. The hindfoot length is 6 to 11 mm. Height of the ear from the notch is 8 to 13 mm. Length of the forearm varies between 36 and 46 mm.

Pelage varies in color from a brick red to a yellowish red. The fur is white at the tips giving these bats a frosted appearance. In general, female bats appear more frosted compared to males, and males have a redder color than females. There is no documented sexual dimorphism in size. The uropatagium is thickly furred on the dorsal side and helps to keep these bats warm in cold weather.

Lasiurus borealis have small and heavily constructed skulls. The arrangement of the 32 teeth is distinctive and shared with other Lasiurus species. Red bats have a tiny cone shaped upper premolar that is located at the inner junction of the upper canine and the second premolar.

Red bats have been called by Allen Kurta, author of "Mammals of the Great Lakes," one of the "most handsome mammals in the Great Lakes region."

Red bats are migratory, arriving in the northern climates in mid-April and leaving in late October. There are records of bats hibernating in the northern parts of their range, but they typically migrate to warmer regions. When red bats hibernate they choose hollow trees. They maintain body temperatures just above freezing and cannot withstand prolonged periods of below freezing temperatures. They may lose up to 25% of their pre-hibernation weight by spring, severely depleting fat reserves (Fenton, 1985).

Lasiurus borealis choose roosting sites in dense foliage. They may be visible hanging from branches or leaves but their coloration helps to camouflage them from predators. Their red coat is particularly helpful at camouflaging them in sycamore, oaks, elm, and box elder trees and they seem to prefer these trees as roost sites (Constantine, 1996). Sites that have been used as roosting areas range from 2 to 40 feet off the ground. The roosting sites of solitary bats have not been as well studied as those of more gregarious bats. Some field workers believe that red bats defend feeding territories. (Constantine, 1966; Fenton, 1985)

Red bats use echolocation to locate prey. They use both broadband and narrow band calls. Search phases of calls use long calls with low pulse repetition of narrow band frequencies.

Red bats are insectivorous. They capture insects while flying like many other insectivorous bats.

Red bats have been found in insect light traps. The activity of these bats around lights reflects overall flight and feeding patterns. Hunting for food begins at dusk and the bat proceeds to hunt within 500 m of a light source (Hickey et al 1996). Foraging activies of this bat are generally concentrated into one feeding bout, but there are records of these bats foraging throughout the night. Their food consists of different kinds of insects: moths, beetles, plant-hoppers, ants, flies, and others.

Red bats make one pass through a concentration of potential prey, fixing on a target within 5 to 10 m. They attack insects, on average, every thirty seconds and are successful fourty percent of the time. If a bat is stalking a moth using echolocation the moth can hear this and will try to flee the attack by diving. The bat will follow the moth into a steep dive and often will pull away within inches of the ground. Humans observing this predator-prey interaction only see the bat and not the fleeing moth and may believe that the bat is acting aggressively towards them.

There is a distinct body and head posturing change in this bat when in pursuit of prey. It has been said that if you observe a rural street light and see a bat dipping and diving, that you are most likely viewing a red bat. (Hickey, Acharya, and Pennington, May 1996)

Predators of red bats include birds of prey and opossums. Humans and human constructions have also taken their toll on red bats. "There have been documented cases of these bats being impaled by barbed wire, . . . entrapped on road surface oil . . ., flying into lighthouses . . ., and radiator grills of automobiles . . ." (Baker, 1983, pg. 123).

Red bats avoid predators through the use of camouflage. (Baker, 1983)

Red bats play an important ecosystem role as insect consumers.

Unfortunately some people view red bats, along with all other bats, as vermin. However, red bats do not negatively affect humans.

Red bats rarely invade homes. Red bats keep insect populations down.

Red bats are secure over most of their range and are not considered threatened.