E-Fauna BC: Electronic Atlas of the Wildlife of British Columbia

Myotis keenii (Merriam)
Keen Bat; Keen's Long-Eared Bat; Keen's Long-Eared Myotis; Keen's Myotis
Family: Vespertilionidae
Species account authors: David Nagorsen and Mark Brigham.
Extracted from the Bats of British Columbia

Photo of species

© David Nagorsen  Email the photographer   (Photo ID #8105)

E-Fauna BC Static Map
Distribution of Myotis keenii in British Columbia
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The information provided below is extracted from the Bats of British Columbia, and may be dated. Check the status section below for current status information.

Species Information

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Illustration Source: Bats of British Columbia by David Nagorsen and Mark Brigham © Royal BC Museum

Keen's Long-eared Myotis is a medium-sized Myotis species with dark, glossy fur and darker indistinct spots on the back of the shoulder; the underside is paler. Its long ears extend beyond the nose when pressed forward; the tragus is long, narrow and pointed. The ears and wing membranes are dark brown but not black. The outside edge of the tail membrane has a fringe of tiny hairs that can be seen with a hand lens. The calcar has an indistinct keel. The skull has a relatively steep forehead.


The Fringed Myotis (Myotis thysanodes), Northern Long-eared Myotis (Myotis septentrionalis) and Western Long-eared Myotis (Myotis evotis) are other Myotis species with a long ear and tragus. However, the distribution of Keen's Long-eared Myotis overlaps only with that of the Western Long-eared Myotis. No external features that we know of will positively distinguish the two species. Keen's Long-eared Myotis has relatively shorter ears, extending less than 5 mm beyond the nose when pushed forward, and its ears are also paler; but these traits are variable and somewhat unreliable. Positive identification can only be made from cranial characters; the distance from the last upper pemolar to the last upper molar is less than 4.2 mm in Keen's Long-eared Myotis and greater than 4.2 mm in the Western Long-eared Myotis.

Dental Formula

incisors: 2/3
canines: 1/1
premolars: 3/3
molars: 3/3


total length: 84 (63-94) n = 33
tail vertebrae: 40 (32-44) n = 33
hind foot: 9 (8-10) n = 32
ear: 18 (16-20) n = 38
tragus: 11 (9-12) n = 41
forearm: 36.0 (34.2-38.5) n = 43
wingspan: 241 (209-262) n = 33
weight: 5.1 (4.0-5.9) n = 35



Mating presumably occurs in autumn. The scanty breeding data consist of a nursing female and juveniles observed on Hot Spring Island in late July; this suggests that the young are born in June or early July.

Food habits have not been investigated, but the diet probably consists of moths and other insects. On Hot Spring Island, Keen's Long-eared Myotis forages over hot spring pools and clearings above salal. Individuals marked with light tags were observed to fly into the tree canopy, but their activity could not be monitored.
Natural History

What little is known about the biology of this bat is derived from incidental observations, information recorded on museum specimens and some research conducted on Hot Spring Island in the Queen Charlotte Islands. It likely uses tree cavities, rock crevices and small caves as roosting sites. There are several records from the vicinity of hot springs and the only known colony occurs on Hot Spring Island. Most of the natural history data for this species comes from the Hot Spring Island population. However, given the unusual ecological situation, it is not clear if this information is applicable to other populations. On Hot Spring a colony of about 70 Keen's Long-eared Myotis, in association with a colony of the Little Brown Myotis, roosts under rocks that are heated by a natural hot spring. Temperatures at the roost entrance in summer range from 22°C to 27°C, whereas the ambient temperature varies from 11°C to 18°C. Because of a warm spring, the roost is quite humid. The roost is situated below the high tide line and it is often submerged for several hours at high tide. During these periods of high tides the roost is abandoned.

There are no winter records, and it is unknown if this species hibernates in coastal regions.


The distributional pattern suggests that Keen's Long-eared Myotis is associated with coast forest habitats.


Keen's Long-eared Myotis is the only North American bat restricted to the Pacific coastal region. The few locality records available suggest that its range extends from the Olympic Peninsula in Washington to southeastern Alaska. In British Columbia, it is found on the coastal mainland as far north as the Stikine River, on the Queen Charlotte Islands and on Vancouver Island.


No subspecies are recognized. In much of the earlier literature, two subspecies were recognized for this bat: M.k. keenii from the coast and M.k. septentrionalis from central and eastern North America. The latter is now considered to be a distinct species Myotis septentrionalis.


Most of the population of Keen's Long-eared Myotis appears to be restricted to British Columbia. In fact, of the known locality records only three are from outside the province: one from Wrangell Island in south­eastern Alaska and two from the Olympic Penninsula in Washington. Specimens of Keen's Long-eared Myotis reported from Stuie, Telkwa and Parksville in previous publications were misidentified; they are the Western Long-eared Myotis.

In response to its apparent rarity and the lack of knowledge about its basic biology, the provincial Ministry of Environment placed Keen's Long-eared Myotis on the provincial Red List. This bat is rare in museum collections, being represented by a small number of specimens from only nine locations in the province, but there is not enough information to determine if it is rare in nature. This species may be common in coastal forests but seldom captured because of its foraging or roosting behaviour.

At present, too little is known about this bat to speculate on its use of old-growth forest habitat. Additional field studies are urgently required to determine the status of this species. Until a reliable field technique is developed to distinguish live Keen's Long-eared Myotis from the Western Long-eared Myotis, field research in areas where the two species coexist is virtually impossible. Because Keen's Long-eared Myotis may be an endangered species, killing animals to identify from cranial traits is clearly unacceptable. Studies are underway to develop a set of external measurements that will separate the two species in the hand.

Status Information

Origin StatusProvincial StatusBC List
(Red Blue List)
NativeS3?BlueDD (Nov 2003)
BC Ministry of Environment: BC Species and Ecosystems Explorer--the authoritative source for conservation information in British Columbia.

Additional Photo Sources

General References

Recommended citation: Author, Date. Page title. In Klinkenberg, Brian. (Editor) 2021. E-Fauna BC: Electronic Atlas of the Fauna of British Columbia [efauna.bc.ca]. Lab for Advanced Spatial Analysis, Department of Geography, University of British Columbia, Vancouver. [Accessed: 2024-06-24 11:31:14 PM]
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