NATURAL HISTORY

TRICOLORED BAT (formerly known as the eastern pipistrelle) } Perimyotis subflavus (previously Pipistrellus subflavus)

FAMILY: Vespertilionidae

DESCRIPTION: The tricolored bat is the smallest bat found throughout the eastern and midwestern states, weighing about 1.5-3 ounces and measuring 3-3.5 inches from head to tail. The species' forearm skin is reddish, and its pelage is yellowish-brown, while each hair, when examined individually, is “tricolored”: brown at the tip of the hair, yellow in the middle, and dark at the base. These bats have oblong ears, which when held toward the nose reach just beyond the tip of the nostrils, and are slow fliers, with an erratic and “fluttery” pattern while foraging.

HABITAT: Tricolored bats appear to inhabit landscapes that are partly open, with large trees and plentiful woodland edges. They are found in a variety of terrestrial habitats, including grasslands, old fields, suburban areas, orchards, urban areas and woodlands, especially hardwood woodlands. They generally avoid deep woods as well as large, open fields. They require specific habitats for hibernating, roosting and foraging.

These bats will hibernate in caves, mines and even buildings with variations in hibernation site selection by region. For example, tricolored bats in the northern part of their range hibernate almost exclusively in caves and mines. They also tend to occupy the very back of the caves and other hibernation sites, where temperature is highest and least variable, the walls of the cave are warmer, and humidity levels are higher.

Tricolored bats will roost in a wide variety of habitats, again varying by region. They may be found in caves, crevices, trees and anthropogenic structures such as barns. They tend to feed over water bodies such as rivers or lakes, where insect populations are highest. They also tend to select for more open foraging sites, with higher canopies where canopies occur at all.

RANGE: The tricolored bat ranges across most of eastern North America and into eastern Central America, and it occurs over much of the midwestern United States.

MIGRATION: Until recently biologists had believed the tricolored bat was a regional migrant, and that like other hibernating bat species it moved, at most, only moderate distances between hibernacula and summer roosting areas. However, recent research suggests some individuals undertake annual latitudinal migrations, more like long-distance migrants such as hoary bats (Lasiurus cinereus) and silver-haired bats (Lasionycteris noctivagans) and that migratory tendency varies with latitude and between sexes.

BREEDING: Mating occurs in the late summer and fall in “swarms” in front of cave openings where females mate with multiple males. Gestation lasts approximately 44 days, and females give birth from spring to early summer. Tricolored bats usually give birth to two, rather than the more typical one, offspring per year. Babies are born hairless and pink, with closed eyes, and the babies can make clicking sounds to help mother bats locate their young. Young tricolored bats begin flying at three weeks and can replicate adult flight and foraging capabilities about one week later. Young are independent at five weeks. Sexual maturity is reached anywhere between 3 and 11 months.

LIFE CYCLE: Tricolored bats have been recorded living anywhere from 4 to 15 years old.

FEEDING: Tricolored bats are strictly insectivorous. They may consume a wide variety of insects depending on relative availability.

THREATS: White-nose syndrome; habitat destruction, including from logging, residential and agricultural development, mineral extraction and sealing of entrances to abandoned mines; environmental contaminants; industrial wind-energy projects; climate change.

POPULATION TREND: Little research and monitoring occurred for this species prior to the onset of white-nose syndrome, but its population has declined by at least 34 percent with varying levels of severity in different regions, depending largely on where WNS has been documented.

Photo by Dave Thomas/Flickr