Description: All myotis are much alike and critical examination is required to tell them apart, but of the myotis in Kansas, Keen's myotis most nearly resembles the little brown myotis. Keen's myotis can be distinguished from other bats in Kansas by: 1) long fine hair which is black at the base and dull (not glossy) brown toward the tips, 2) belly lighter and grayish, 3) wing membranes attached to the base of the toes, 4) long, slender ears (16-18 mm from notch) which when pulled forward extend about 4 mm beyond the nostrils, 5) long, slender and pointed tragus, 6) fourth and fifth fingers about equal in length, and 7) a calcar with a slight keel.
Size: Adults may attain the following dimensions: total length 86-99 mm; tail 36-43 mm; hind foot 8-10 mm; ear 16-18 mm; weight 5.2-8.4 grams.
Range and Habitat: This bat is a permanent resident of Kansas, and is known from restricted areas in the north-central and central part of the state where it hibernates alone in caves, mines, or storm-sewers. It spends the summer months outside caves, roosting in trees and buildings. Dates of capture indicate that there is local movement from winter to summer homes.
Reproduction: Reproductive information about this relatively uncommon bat is scanty, but it is known that in small summer nurseries a single young is born to each breeding adult female. Nursery colonies have been found under the loose bark of dead trees, and under shingles.
Habits: This species appears to be less gregarious, hence less easily observed, than other kinds of myotis found in Kansas. In summer it favors woodlands, and since it roosts singly or in small groups, in trees or under bark, is easily overlooked. Caves, mines or storm sewers are sought by this bat in late September or early October, and it joins other species of bats at such sites. At such localities Keen's myotis usually hibernates alone or in small groups, often wedged into cracks or holes. It is easily overlooked at these sites among the more conspicuous species, such as the little brown myotis and big brown bat.
Food: This bat forages mainly among trees in upland forests, often at shrub height beneath the canopy. Its nocturnal activity starts about the same time as the little brown myotis, with one peak several hours after sunset, followed by a lull, and a second bout of foraging towards dawn.
Remarks: The flight of the Keen's myotis is more direct and stronger than the little brown myotis. Predators of this bat are those that gain entrance to their winter hibernacula, or prey upon them while they forage at night. Maximum longevity of this bat is about 18 years.