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Northern long-eared bat

The common name of this bat is an honor of the Reverend John Henry Keen who, in 1894, obtained the first specimen from which the species was described. Keen’s myotis is brown in color, darker above than below, and its fur is silky, not glossy like that of the little brown bat which it resembles. The ears of this species are long, narrow, and extend at least 4 mm (0.16 in) beyond its nose when pressed forward along the face. The tragus, a fleshy structure situated at the base of the bat’s ear, are projecting upward, is relatively longer, and pointed at the tip in Keen’s myotis, in contrast to the shorter, blunt-tipped tragus of the little brown bat.  Keen’s myotis is 75-95 mm (3.0-3.7 in) in total length, weighs 7-9 g (0.2-0.3 oz), and has a wingspread of 23-28 cm (9-11 in)

(Myotis septentrionalis)From: Saunders, D. A. 1988. Adirondack Mammals. State University of New York, College of Environmental Science and Forestry. 216pp.

Order: Chiroptera
Family: Vespertilionidae

Taxanomic note from IUCN web site

Myotis septentrionalis formerly was included in this species. Koopman (1993) included septentrionalis in M. keenii, but van Zyll de Jong (1985), and Simmons (2005) recognized M. keenii and M. septentrionalis as distinct species. Most literature references to M. keenii actually pertain to Myotis septentrionalis. A recent molecular study using mtDNA (cytochrome b gene) (Tanya Dewey, unpublished data) supports the close relationship of M. keenii and M. evotis and their distant relationship to M. septentrionalis."

Saunders refers to Myotis septentrionalis as Myotis kennii in his book.

Range and Habitat

The range is from central Saskatchewan, east to the Atlantic coast, and south to northern Florida. Within its geographic area, the species varies from locally abundant to uncommon or absent. Too few summer records exist for the Adirondacks to define its local range. However, it is a likely summer resident throughout the Park. Keen’s myotis is usually present in mines and caves used by other Adirondack bat species for winter roosts. Summer roosts are behind the loose bark of trees, shutters and shingles of buildings, or within buildings.

Food and Feeding Behavior

This bat takes a large variety of flying insects (caddis flies, mayflies, leafhoppers, beetles, moths, and lacewings) between the shrub layer and canopy of the forest. It frequently forages over ridges and along hillsides, and may glean some insects from tree foliage. Feeding flights are longest just after dusk and before dawn.

Activity and Movement

The activity and hibernating schedules are not well-known. Although the usual occupancy of caves is from mid-October through March or April, some individuals enter as early as mid-August. They hibernate in holes, cracks, and crevices but also in exposed sites, usually free of drafts, and where the temperature is near 4.5 degrees C (40 degrees F), in mines and caves.


Very little is known about the reproductive biology of Keen’s myotis. Mating occurs in autumn, but fertilization is delayed until spring. Females select maternal sites in and around buildings, but also in hollow trees and behind loose bark. They bear only one young per year, in late June or July. This species has a life span of at least 18.5 years


There are no documented predators of this species. It is likely the same animals that prey upon the little brown bat also take Keen’s myotis.

Social Behavior

  • Social System - Keen’s myotis is promiscuous. Males are solitary during the summer. Pregnant females form maternal colonies of several to 30. Although this species may join clusters of other hibernating bats, it usually roosts alone or in small groups. Occasionally, it hibernates in groups of several hundred.
  • Communication- Unknown. 

Additional References

Fitch, J.H. and K.A. Shump. 1979. Myotis keenii. Mammalian Species, 121:1-3.

Griffith, L.A. and J.E. Gates. 1985. Food habits of cave dwelling bats in the central Appalachians. Journal of Mammalogy, 66:451-460.