254.

Eastern Red Bat

Lasiurus borealis

French: Lasiure boréal / German: Rote Haarschwanzfledermaus / Spanish: Lasiuro boreal

Other common names: Red Bat

Taxonomy. Vespertilio borealis P. L.. S. Muller, 1776,

New York, USA.

See L. egregius . Lasiurus borealis is in the Red Bat group. Monotypic.

Distribution. From S Canada (extreme SE Saskatchewan, S Manitoba, S Ontario, S Quebec, New Brunswick, and Nova Scotia) S through C & E USA to NE Mexico.

Descriptive notes. Head-body c¢.55-2— 59.6 mm, tail 45-62 mm, ear 7-13 mm, hindfoot 6-11 mm, forearm 35- 7-46 mm; weight 7-16 g. Females are larger than males. Hairs are dense and long; upperparts are bright red to pale red, washed with white, and pale white patch occur on shoulders. Underparts are slightly paler. Ears are wide, short, and rounded, with basal two-thirds of outer part furred. Distal end of tragus is triangular. Wing membranes are dark; uropatagium is densely furred throughout. Claws are black; calcar is about twice as long as hindfoot. Skull is short and broad; braincase is high and rounded; palatal emargination is wider than depth; floor of braincase and palate are not parallel. Teeth are large, P? is minute and displaced inward, and upper molars are broad on inner side. Dental formulais11/3,C1/1,P 2/2, M 3/3 (x2) = 32. Chromosomal complement has 2n = 28 and FN = 48, with medium-sized submetacentric X-chromosome and small acrocentric Y-chromosome.

Habitat. Xeric shrublands, thorny forests, and deciduous forests at elevations of 400- 1600 m.

Food and Feeding. Right after emerging from day roosts, Eastern Red Bats fly high, slowly, and erratically during the first 15-30 minutes. Afterward they descend and start foraging from treetops to almost ground level. At this time, they fly straight or in wide circles, and this pattern is only altered during insect captures. They might forage in groups, and individuals have been observed flying low over waterto capture insects and drink,at crowns of trees, and near streetlamps. They seem to establish feeding territories. Moths were most abundant (26-2% by volume) in stomach contents from Indiana. Eastern Red Bats are known to eat Homoptera, Coleoptera, Diptera, Hymenoptera, Orthoptera, Hemiptera, and Lepidoptera, including flies, beetles, crickets, and cicadas.

Breeding. Mating of Eastern Red Bats takes place in flight, and breeding usually occurs in August-September, with sperm being stored until spring. Gestation lasts 80-90 days, and young are observed in May-July; parturition occurs mostly in June; and litters have 1-5 young (average 2-3). Pregnant females have been captured in June and lactating females from late June to early August. Young take c.5 weeks to learn how to fly and forage by themselves.

Activity patterns. The Eastern Red Bat starts foraging 1-2 hours after sunset; some individuals feed throughout the night. Individuals become active at temperatures of 13-20°C, which helps them to avoid unnecessary pauses in hibernation during temperature shifts. Densely and thickly furred uropatagium helps keep them warm during cold weather. Eastern Red Bats roost in dense foliage of trees and shrubs; roosts have been found in edge habitats near streams, openfields, and urban areas. Roosting sites can be from ground level up to 12 m aboveground. When roosting, Eastern Red Bats can be seen hanging from branches or leaves, but their reddish color acts as a camouflage from predators. Some trees such as sycamores, oaks, elms, and box elders seem to be preferred as roosting sites because they provide camouflage due to pigmentation and density of leaves. Echolocation calls are shallow FM sweeps that last more than 5 milliseconds, and frequencies vary mainly from 40 kHz to 45 kHz. Predators include domestic cats, Virginia Opossums (Didelphis virginiana), diurnal raptors, owls, great roadrunners (Geococeyx californianus), and blue jays (Cyanocitta cristata).

Movements, Home range and Social organization. The Eastern Red Batis solitary, except for family groups formed by females and young. It typically migrates to warmer regions, forming migration groups; however, males and females migrate at different times and have different distributions in summer. Some non-migratory individuals in the northern part of the distribution hibernate in hollow trees. Migrating individuals arrive in the north in mid-April and leave in late October. Numbers of individuals in the southern part of the distribution increase from December to March. Body temperature is kept just above freezing, and they cannot tolerate long periods of below freezing temperatures. Fat reserves are severely depleted during hibernation; they can lose up to 25% oftheir autumn pre-hibernation body weight. Some individuals come out of hibernation during warm days to feed before dusk. Individuals can fly more than 2 km from day roosts to forage, and mean forage areas are 62-146 ha.

Status and Conservation. Classified as Least Concern on The IUCN Red List. The Eastern Red Bat is widely distributed, populations are presumably large, and it occurs in protected areas.

Bibliography. Alvarez-Castafieda & Gonzalez-Ruiz (2018), Arroyo-Cabrales et al. (2016), Baird et al. (2015), Baker & Patton (1967), Constantine (1966), Elmore et al. (2005), Fenton (1985a), Fenton, Merriam & Holroyd (1983), Morales et al. (2014b), Myers & Hatchett (2000), Novaes, Garbino et al. (2018), Shump & Shump (1982a), Simmons (2005), Wilson & Ruff (1999).