Gray Myotis (Gray Bat)

Myotis grisescens

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Photo of four gray myotises clinging to a cave ceiling.
Gray myotis conservation focuses on protecting their wintering and nursery caves from human disturbance, reducing pesticides, and maintaining wooded corridors along streams.
Shelly Colatskie
Endangered
Species of Conservation Concern
Family

Vespertilionidae (evening bats) in the order Chiroptera

Description

The gray myotis, or gray bat, is the largest of all Missouri’s myotis (mouse-eared) bats, which include the little brown myotis, the Indiana myotis, and the northern long-eared myotis. Gray myotises are hard to distinguish from their myotis cousins. Gray myotises have grayer fur; it is a uniform brownish gray most of the year, turning a light rusty brown in summer. Other myotises have bi- or tricolored fur, with the tips of each strand contrasting with the base. The gray myotis’s ears and wing membranes are gray to black. Its key identifying feature is wings that attach to the ankle and not at the base of the toes. The gray myotis also has a distinct notch on the inside curve of each claw.

Size

Length: 3 inches; wingspan: 10-12 inches; weight: 1/3 ounce.

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Photo of a gray bat clinging to a cave ceiling.
Gray Myotis (Gray Bat)
Missouri contains about 20 percent of the total population of gray myotises.

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Photo of several members of a gray myotis colony clinging to a cave ceiling.
Gray Myotis Colony
It is important for people to stay out of nursery caves: if disturbed, pregnant females may abort their young, and babies may drop from the wall to the floor or stream below and die.

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Photo of a gray myotis colony of approximately 3,000 individual bats, clinging to a cave ceiling.
Gray Myotis Colony
This gray myotis colony contains about 3,000 individuals. Several factors threaten this species' survival.

gray_bat.jpg

Photo of a gray myotis hanging from a cave ceiling.
Gray Myotis (Gray Bat)
Gray myotises are endangered. This one is not looking like a particularly healthy individual.
Habitat and conservation

This species once flourished in limestone caves, especially caves within two miles of rivers, streams, or lakes. Conservation efforts include protecting known gray myotis wintering and nursery caves from disturbance, reducing the use of pesticides (which not only affect their prey but also accumulate in the bat's tissues and mother's milk), and maintaining wooded corridors along streams. White-nose syndrome, a deadly fungal disease, is a new and grave threat to this species' survival.

Foods

Insects, including caddisflies, moths, stoneflies, mayflies, flying beetles, true flies, and moths. The Asiatic oak weevil is a favorite summertime food, when it is abundant in forested cliffs along rivers. Most insects are eaten "on the wing."

image of Gray Myotis Gray Bat Distribution Map
Distribution in Missouri

Missouri contains about 20 percent of the total population of gray myotises. Most of the known gray myotis caves are south of the Missouri River, particularly in the Ozarks, although a few exist north of the river.

Status

Listed as Endangered by both the Missouri Department of Conservation and the U.S. Fish and Wildlife Service.

Life cycle

Pregnant females roost in maternity colonies in caves separate from males and young females from late May to June. Each female gives birth to a single young in June. The young are able to fly 4 weeks later. Mothers and young rejoin the bachelor colonies in July and August. Gray myotises exhibit great loyalty to their roosting and hibernating sites and will return to the same caves year after year.

Human connections

Bats eats untold numbers of flying insects. It is important for people to stay out of nursery caves: If disturbed, pregnant females may abort their young and babies may drop from the wall to the floor or stream below and die. A single disturbance can wreck a colony’s reproduction for the year.

Ecosystem connections

Bats help control populations of flying insects. Their presence in caves is a crucial part of those unique underground ecosystems. By collecting organic material (insects) from outside the cave and bringing it in (as guano), bats help provide the basis for a variety of cave life forms.