tri-colored bat

VU - Vulnerable

N2N3 - Vulnerable to Imperiled

S3 - Vulnerable

Proposed Endangered

Special Concern

Species in Greatest Conservation Need

Tri-colored bat, formerly called eastern pipistrelle, is a small vesper bat. It occurs in the United States east of the Great Plains, in southern Canada from Nova Scotia to Ontario, and in Mexico. It was once thought to be one of the most common bats within its range. Its numbers have declined significantly since 2006 due to spreading of the fungal disease white nose syndrome, and to mortality from wind turbines.

Tri-colored bats are found in woodlands near water. They tend to avoid deep forests and open fields. They roost alone, often in trees, but also in rock crevices and in buildings. They hibernate from October to April in caves and mine tunnels, usually in the deeper parts with higher temperatures.

Tri-colored bat is one of the smallest bats in eastern North America and is the smallest bat in Minnesota. Adults are 3″ to 3½″ (77 to 89 mm) in length, have an 8⅝″ to 10″ (220 to 250 mm) wingspan, and weigh 0.16 to 0.28 oz (4.6 to 7.9 g). Females are larger than males. Like most bats, they have two mammae.

The fur (pelage) is usually yellowish-brown overall, but individual hairs are distinctly tri-colored: dark gray at the base, yellowish-brown in the middle, and dark brown or reddish-brown at the tip. This is the feature that gives tri-colored bat its common name and helps to distinguish it from similar species.

The ears, snout, and skin are pinkish. The ears are not particularly large. The fleshy projection at the base of each ear (tragus) is short and blunt. The small size and blunt tragus distinguish tri-colored bat from all other bats in Minnesota. The skull has 34 teeth. No other bat in Minnesota has 34 teeth.

The wing-like flight membrane (patagium) is composed of skin and associated tissues between the neck and the first digit of the forelimb (propatagium), between the digits of the forelimb (dactylopatagium), between the last digit and the hind limb (plagiopatagium), and between the tail and the hindlimb (uropatagium or interfemoral membrane). The membrane is blackish, and the forearm is reddish. The forearm length is 1¼″ to 1⅜″ (31.4 to 34.1 mm). The upper side of the interfemoral membrane is densely covered with fur just on the basal third. The tail extends to the end of the interfemoral membrane but not beyond it. A spur of cartilage (calcar) extends from the ankle along the outer part of the interfemoral membrane, which it helps to extend in flight. The calcar does not have a keel.

Total length: 3″ to 3½″ (77 to 89 mm)

Wingspan: 8⅝″ to 10″ (220 to 250 mm)

Tail: 1⅜″ to 1⅝″ (34 to 41 mm)

Forearm length: 1¼″ to 1⅜″ (31.4 to 34.1 mm)

Weight: 0.16 to 0.28 oz (4.6 to 7.9 g)

Woodlands

4 to 8 years

Moths, flies, beetles, and ants

Sources

4, 6, 7, 24, 29, 30, 76.

This species was previously classified as Pipistrellus subflavus. A morphological review (Menu, 1984) contended that it was more similar to the genus Myotis, and proposed transferring it to a new genus Perimyotis. The proposal was not widely accepted. A recent molecular phylogenetics study of the family Vespertilionidae (Hoofer, 2003) showed that it does not belong in the genus Pipistrellus, and confirmed its placement in the genus Perimyotis.

Perimyotis subflavus was previously known by the common name eastern pipistrelle. It was incorrectly believed to be closely related to the European genus Pipistrellus.

Bats on the bathroom wall on Picnic Island in Fort Snelling State Park.

Location: Fort Snelling State Park

Bats on the bathroom wall on Picnic Island in Fort Snelling State Park.