(Lasiurus borealis Muller)From: Saunders, D. A. 1988. Adirondack Mammals. State University of New York, College of Environmental Science and Forestry. 216pp.
Description: Red bats vary in color from brick red to buffy orange. The hairs of the back, and to a lesser extent, those of the chest, are tipped with white. Males tend to be less frosted with white, but are brighter in color than females. Both sexes have a buffy white shoulder patch. The unfurred portion of the tail membrane and wing membranes are brownish black. The short, rounded ears and front limbs are rusty orange. The fur is dense and wooly. The total length is 95-126 mm (3.7-5.0 in). Females are larger than males. Weight varies from 8-15 g (0.3-0.5 oz). When fully extended in flight, the narrow pointed wings have a span of 29-33 cm (11.4-13.0 in).
Range and Habitat: The range is from most of the southern half of Canada to Argentina and Chile, excluding the Rocky Mountains, some central western states, and the southern two-thirds of Florida in the U.S. This summer resident of the Adirondacks may be more widespread than the few records of its occurrence indicates. Its solitary life style makes it less noticeable than colonial bats occupying buildings, mines, and caves. In most of the Northeast, the red bat is uncommon to rare. Merriam regarded this species as one the least common bats of the Adirondacks.
Food and Feeding Behavior: At the onset of its foraging flight 1-2 hours after sunset, the red bat flies slowly in an erratic pattern high over forests, forest edges, meadows, and fields, descending after 15-30 minutes to feed between ground and tree top heights, and adopting a straighter course or flying in a series of arcs. Individuals return to forage nightly over the same areas, usually within 300 m (1000 ft) of their day roosts. Several may forage in close proximity with no apparent antagonism. Bouts of foraging may occur intermittently until dawn, but are most frequent in the hours following sunset and preceding dawn. Beetles and moths comprise 54 % by volume of the diet of a sample of 128 red bats from Indiana, but they also consumed large insects of many orders. Red bats often catch insects attracted to street and yard lights.
Activity and Movement: By day, red bats roost in the foliage of deciduous trees 1-12 m (3-40 ft) above the ground, selecting perches that are open from below to permit easy access, but otherwise densely shaded to hide them from predators. While roosting, this species hangs by one or both feet, and resembles a dead leaf. In September and October, red bats leave the Adirondacks, migrating into the southern parts of the range, and not returning until mid May or June. On a level, straight course, the flight of this bat is swift, and it may attain a speed of 64 km/h (40 mph).
Reproduction: Red bats breed in August and September. Pairs initiate copulation while flying, sometimes fluttering to the ground. Fertilization does not occur until spring. The gestation period is 80-90 days, after which the female produces a litter of 1-5 (average 2 or 3) young, the largest litter size of any bat. Females bear their annual litter in late June or July. The young remain at the roost while their mother forages, grasping her with their wings and teeth to nurse when she returns. The young nurse until 35-42 days old when they become independent and disperse. Little is known about age of first breeding and longevity of the red bat, but the potential life span may be 12 years.
Predators: Blue jays prey upon young red bats. Great horned owls, merlins, American kestrels, sharp-shinned hawks, and opossums are occasional predators of adults.
- Social system - The red bat is promiscuous. For most of its life, this species is solitary except during mating and when a female cares for her young. Temporary associations occur during foraging, and at least for some, during migration (groups of 100 have landed on ships 100 miles from the Atlantic coast). In some parts of the range, red bats swarm at the entrances to caves in August, although they do not use them as winter shelters. Swarming may facilitate mating.
- Communication - While the communication of this species has not been studied, several anecdotal observations suggest a role for vocal and chemical signals in regulating social encounters. Migrating individuals may select the same perches used by red bats during previous nights, perhaps responding to chemical cues placed on the perch. The four sets of facial glands are likely sources of substances. Caged red bats decoy free-ranging individuals, a fact that biologist use to their advantage when attempting to capture this species. In flight, red bats chirp and squeak, as well as emit pulses of high frequency sounds. When handled, they produce raspy, buzzy sounds.
Shump, K.A. Jr., and A.V. Shump. 1982. Lasiurus borealis. Mammalian Species, 183:1-6.