NORTHERN LONG-EARED BAT } Myotis septentrionalis

FAMILY: Vespertilionidae

DESCRIPTION: This is a medium-sized bat; adult weight is approximately .25 ounces and total body length is approximately 3.5 inches. As its name suggests, this bat is distinguishable from other Myotis species by its long ears, which extend beyond its nose when pushed forward (average length .625 inches). This species is similar in color to the little brown bat, with back fur dullish yellow-brown with brown shoulder spots, and belly fur pale gray. Females tend to be slightly larger and heavier than males.

HABITAT: Northern long-eared bats overwinter in caves or abandoned/inactive mines in multi-species hibernacula and generally comprise a small proportion (generally less than 25 percent) of the total number of animals hibernating at each site. The bat seems to favor deep crevices for hibernation.

At summering sites the presence of northern long-eared bats is correlated with the availability of features most often found in older forests — generally those comprised primarily of trees 100 years old or older — such as uneven forest age, a multi-layered canopy, single and multiple tree-fall gaps, standing snags and abundant woody debris. There is no evidence that the species absolutely requires primary (never logged) forest habitat, but its presence and activity level is consistently highest in forest stands with late-successional characteristics, which the species may favor for the large, partially dead or decaying trees on which this bat relies for rearing young, and which males and nonreproductive females use as day roosts. Older forests may be preferred for foraging, as well.

On the western edge of its range (the Dakotas, Montana, Wyoming), this species is found in wooded riparian zones within badlands or prairie habitat at low elevation, and in dense forest at higher elevations.

RANGE: The northern long-eared ranges widely across much of Canada and the United States, but it is patchily distributed and rarely found in groups of more than 100 bats. It occurs in all Canadian provinces; in the Yukon and Northwest Territories; and in eastern, midwestern and some southern states. A small number of sightings have also been reported in Montana and Wyoming. It is considered vulnerable or imperiled across much of its range, but is rarer in the southern portion of its range than the northern portion (and relatively rare in the northwestern portion).

MIGRATION: Though this species is not considered migratory, many groups or individuals travel considerable distances  — up to 35 miles — between winter hibernacula and summer roosting sites.

BREEDING: Mating takes place in late summer or early fall, and females store sperm until they emerge from hibernation in the spring, when ovulation and fertilization occur. Some individuals mate again upon emergence. Gestation lasts 50–60 days, and parturition occurs in early to mid-summer. Females bear a single offspring annually, and young-of-the-year may mate prior to hibernation in the fall. Though some may roost alone, females often roost colonially; maternity or nursery colonies may be comprised of up to 90 individuals, including young. The largest maternity colony reported contained 39 adult females. Females exhibit high site fidelity to maternity roosts, returning annually to their natal sites.

LIFE CYCLE: The lifespan of northern long-eared bats may be longer than 18 years.

FEEDING: Like other Myotis species, the northern long-eared bat feeds opportunistically on insects, using both “hawking” and “gleaning” to obtain prey. The species feeds on a variety of insects, including moths, beetles and flies, though its diet varies both seasonally and geographically.

THREATS: This bat is threatened by white-nose syndrome; habitat destruction, including from logging, residential and agricultural development, mineral extraction, and the sealing of entrances to abandoned mines; environmental contaminants; wind energy; and climate change.

POPULATION TREND: This species has declined dramatically in the eastern portion of its range due to white-nose syndrome. As the disease spreads westward, it is likely to decline throughout its entire range.

Photo courtesy Pete Pattavina/USFWS