Myotis keenii

"Keen's myotis is a medium-sized bat with a long tail. It does not demonstrate narrowly specialized habitat needs. It roosts in caves and trees in the summer, sometimes in small colonies. The bats hunt insects at night and are most active shortly after sunset and shortly before dawn. Larger groups of bats form colonies to hibernate together in the winter, sometimes in the same hibernaculum as other species of bats.  As with other bats that hibernate, breeding takes place in the fall, but the fetus does not develop until spring. In the summer, males usually roost separately from females and their young."

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Global Range: (20,000-200,000 square km (about 8000-80,000 square miles)) The range includes western Washington, British Columbia (including Vancouver Island, the Queen Charlotte Islands, and coastal mainland), and a few localities in southeastern Alaska MacDonald and Cook 2009). This species has one of the smallest distributional ranges of any North American bat (Van Zyll de Jong 1979, 1985). Misidentifications have somewhat obscured the precise distribution (Johnson and Cassidy 1997, MacDonald and Cook 2009). Reid (2009) incorrectly stated that this species occurs on Wrangell Island, Siberia.

The range includes coastal Washington, British Columbia (including Vancouver Island, the Queen Charlotte Islands, and coastal mainland), and southeastern Alaska (e.g., Hoonah, Wrangell, Ketchikan) (Parker and Cook 1996; Simmons 2005). This species has one of the smallest distributional ranges of any North American bat (Van Zyll de Jong 1985).

Myotis keenii has one of the most restricted ranges of any temperate vespertilionid bat, being found only in the coastal forests of the Pacific Northwest, extending as far north as southeast Alaska, and reaching as far south as the state of Washington with the bulk of its range contained in British Columbia. This species of bat is restricted to warm maritime forests in which prey and roosting sites are abundant. Keen's bats may make small-scale movements to suitable hibernacula but do not migrate.

Biogeographic Regions: nearctic (Native )

occurs (regularly, as a native taxon) in multiple nations

Canada

Origin: Native

Regularity: Regularly occurring

Currently: Present

Confidence: Confident

Type of Residency: Year-round

United States

Origin: Native

Regularity: Regularly occurring

Currently: Present

Confidence: Confident

Type of Residency: Year-round

Myotis keenii is a medium sized vespertilionid with dark brown fur on its back, often with darker patches at the shoulders, and lighter fur on its underbelly. The ears, when laid forward, reach just beyond the nose and possess a long, slim pointed tragus. Ear length ranges from 13 to 20 mm. The ears, wings and uropatagium are a dark brown color, sometimes almost black, with the uropatagium possessing minute intermittent hairs at its edge. The calcar supporting the uropatagium generally lacks a conspicuous keel and the skull includes a steeper forehead than that of its close relatives, M. evotis and M. thysanodes. A large degree of overlap in external characteristics, such as forearm and ear length and pelage and membrane color, makes it impossible to distinguish M. keenii from its closely related congener, M. evotis. Myotis keenii is also easily confused with M. septentrionalis and M. lucifugus, as all have extensive overlap in external characteristics as well. Finally, the closely related M. thysanodes may be confused with M. keenii when the tail membrane is not conspicuously fringed. Reliable species identification may only be effected by genetic analysis or by analysis of cranial measurements. Myotis keenii has a wingspan ranging from approximately 20 to 26 cm, an overall length of 40 to 55 mm and an average weight ranging from 4 to 6 grams. There is no documented sexual dimorphism.

Range mass: 4 to 9 g.

Average mass: 6 g.

Range length: 40 to 55 mm.

Range wingspan: 21 to 26 cm.

Average wingspan: 24.1 cm.

Other Physical Features: endothermic ; heterothermic ; bilateral symmetry

Sexual Dimorphism: sexes alike

Length: 9 cm

Length:
Range: 40.4-55 mm

Weight:
Average: 5 g
Range: 4-6 g

Distinguished from sympatric western long-eared Myotis (Myotis evotis) by ear length--when laid forward, they extend less than 5 mm beyond the tip of the nose. Additionally, the length across the upper molars and last premolar in M. keenii is less than 4.2 mm, whereas it is greater than 4.2 mm in Myotis evotis (van Zyll de Jong 1985, Nagorsen unpubl. ms.).

Comments: The distributional range suggests an association with coastal forest habitat (van Zyll de Jong 1985, Nagorsen and Brigham 1993). Apparently this bat is associated with mature forests (Balcombe, 1988 COSEWIC report). In southeast Alaska, this bat is associated primarily with coniferous forests, and females may be associated mainly with old-growth forests, especially cedar (Thuja, Chamaecyparis) trees in riparian areas (Boland 2007). However, it is not restricted to old growth (COSEWIC 2003). Across the range it has been found roosting in southwest-facing rock crevices, among geothermally heated rocks, in tree cavities, in bark crevices, and in buildings (D. Burles, pers. comm.; Firman et al. 1993; Nagorsen and Brigham 1993; Parker and Cook 1996; Mather et al. 2000). Tree cavities and loose bark are important natural roost sites and may be limiting in some parts of the range (British Columbia Ministry of Water, Land and Air Protection 2004). In British Columbia, one maternity colony (on Hot Springs Island in the Queen Charlotte Islands) is situated within geothermally heated rocks associated with hot spring activity (British Columbia Ministry of Water, Land and Air Protection 2004). The only other known maternity colony in British Columbia was suspected to be in a tree located in a low elevation, southwest-facing cliff at Knoll Hill near Tahsis, Vancouver Island (COSEWIC 2003). Known maternity roosts and summer feeding areas in British Columbia are at elevations below 240 meters; known hibernation sites occur above 400 meters in caves over 100 meters long (British Columbia Ministry of Water, Land and Air Protection 2004). These bats have been observed foraging over hot spring pools and clearings above scrubby salal (Gaultheria shallon).

Habitat and Ecology

Systems

• Terrestrial

The foraging environment for M. keenii is large coastal old growth forests in which prey density is sufficient. The preferred roosting habitat for this species includes the loose bark of large trees, caves, snags, hollow trees, and human made structures such as bridges and house attics. Myotis keenii is believed to hibernate or overwinter in caves, called hibernacula, found scattered about the coastal range these bats inhabit. Hibernacula are only known from caves in karst formations. Maternity roosts are known only from a hydrothermally heated system of rock crevices and a lodgpole pine snag (Pinus contorta). Since these bats are difficult to capture and there are only a few colonies that have been studied, many inferences about their ideal habitat and behavior have been made based only only a few observations.

Range elevation: 0 to 1100 m.

Habitat Regions: temperate ; terrestrial

Terrestrial Biomes: forest

Other Habitat Features: suburban ; riparian ; estuarine ; caves

Non-Migrant: No. All populations of this species make significant seasonal migrations.

Locally Migrant: No. No populations of this species make local extended movements (generally less than 200 km) at particular times of the year (e.g., to breeding or wintering grounds, to hibernation sites).

Locally Migrant: No. No populations of this species make annual migrations of over 200 km.

Foods of choice for M. keenii include: spiders, caddis flies, mosquitoes, flies, moths, midges and other assorted flying insects. Having a prey base that includes flying and non-flying prey is thought to give the bats flexibility with respect to environmental conditions that may be adverse for catching certain types of prey. Although M. keenii is adept at catching flying insects, the preferred source of food appears to be spiders and Lepidoptera which, in the Gandl K’in Gwaayaay (Hotspring Island) study, were present in approximately 78% of the pellet material obtained from maternity roosts. Prey choice is likely dependent on prey abundance.

Animal Foods: insects; terrestrial non-insect arthropods

Primary Diet: carnivore (Insectivore )

Comments: Insectivorous. Known foods include spiders, tricopterans, moths, and flies (D. Burles, pers. comm.; Parker and Cook 1996).

Since low numbers of Myotis keenii have been captured, the current assumption is that the overall species numbers are low. This would lead one to believe that M. keenii is not a significant prey item for either predatory raptors or terrestrial predators. However, despite their low numbers, their specialization on moth prey makes them potentially important predators of moths in the areas in which they live.

Actual predation information for M. keenii is not available although bats of the Vespertilionidae family in general are thought to fly mainly in darkness to maximize predator avoidance. Expected predators are owls, hawks, cats, raccoons, snakes, and some carnivorous rodents, such as Peromyscus spp., that are a threat to bats while roosting.

Note: For many non-migratory species, occurrences are roughly equivalent to populations.

Estimated Number of Occurrences: 21 - 80

Comments: The species is known from 25 locations in Canada, where only a couple maternity colonies have been identified (COSEWIC 2003). The only known hibernacula in British Columbia are on northern Vancouver Island where M. keenii has been found in 8 caves from 3 separate areas (COSEWIC 2003). The species is known from just a few locations in southeast Alaska (MacDonald and Cook 2009) and several sites in western Washington (Johnson and Cassidy 1997).

Unknown

Comments: Total adult population size is unknown but presumably is at least several thousand. This species is relatively rare in museum collections, but whether this indicates true rarity is unknown (MacDonald and Cook 2009). A maternity colony in British Columbia included about 40 reproductive females (COSEWIC 2003).

Very little is known (van Zyll de Jong 1985). This is believed to be a solitary species. It is reported to fly rather slowly while foraging.

Communication specifics are not well understood for M. keenii. Vespertilionid bats have well-developed vision, but to what extent vision is used is unknown in M. keenii. Myotis keenii have very accurate echolocation, coupled with capability of highly maneuverable flight, that allows them to fly in adverse weather as well in dense forests, which other bat species seem to avoid. This also gives them the ability to detect and glean prey that are stationary on trees, leaves, and rocks. Unfortunately, for researchers, this also makes them rather difficult to capture using standard mist net and harp trap techniques, and subsequently, hard to study. Whether this species uses their sense of smell extensively has not been tested although it is reasonable to assume they use their sense of smell in offspring recognition as in other mammals.

Communication Channels: acoustic ; chemical

Perception Channels: visual ; acoustic ; ultrasound ; echolocation

Little information on the longevity of M. keenii is available. Recapture records from the Gandl K’in Gwaayaay (Hotspring Island) study show a maximum documented recapture age of 12 years and 11 months. This is believed to be an underestimate of total lifespan since other Myotis species have documented life spans of 13 to 22 years.

Range lifespan
Status: wild: 13 (high) years.

Average lifespan
Status: captivity: 19 years.

Maximum longevity: 19 years (wild)

No information is available on the mating systems of M. keenii. Most temperate zone vespertilionids mate at hibernacula in the fall. Mating at hibernacula is often characterized by "swarming" and is likely to be indiscriminate.

Only one study, the Gandl K’in Gwaayaay (Hotspring Island, Gwaii Haanas National Park) study, reports reproduction information for M. keenii in detail. However the colony studied is based out of a hydrothermal maternity roost that may provide information unrepresentative of other colonies of the same species due to the unique nature of the roost. Similar to other Myotis species, M. keenii are assumed to mate in autumn or early winter before entering hibernation, hold the sperm until spring, then ovulate and become pregnant upon their spring awakening.

Upon leaving the winter hibernacula, pregnant females will journey to maternity roosts in early summer (April or May) where they will stay until the young are born. Female M. keenii will produce one offspring per year after a relatively long gestation period of approximately 40 to 60 days. Newborn bats are generally capable of flight three weeks after birth but are not weaned until they are capable of fending for themselves, thus the young bats have a total rearing time of approximately five to six weeks. The young are believed to become sexually mature near the end of their first summer, or breeding season, but are not expected to breed until their second breeding season.

Breeding interval: Myotis keenii breed annually just prior to hibernation.

Breeding season: Mating occurs in autumn, in approximately the month of September.

Range number of offspring: 1 to 1.

Range gestation period: 40 to 60 days.

Range weaning age: 21 to 42 days.

Average weaning age: 35 days.

Range time to independence: 3 to 6 weeks.

Average time to independence: 5 weeks.

Average age at sexual or reproductive maturity (female): 12 months.

Average age at sexual or reproductive maturity (male): 12 months.

Key Reproductive Features: iteroparous ; seasonal breeding ; gonochoric/gonochoristic/dioecious (sexes separate); viviparous ; sperm-storing ; delayed fertilization

Average number of offspring: 1.

Female M. keenii provide nourishing milk and protection for their young until they are capable of flight and foraging on their own. At the end of the summer (August to September), when young have become independent, female M. keenii leave for their winter hibernacula. Growth in vespertilionid bat young is rapid, with young growing to adult size, attaining flight, training in the use of echolocation, and attaining independence within six weeks of their birth. Males are not involved in parental care.

Parental Investment: altricial ; pre-fertilization (Provisioning, Protecting: Female); pre-hatching/birth (Provisioning: Female, Protecting: Female); pre-weaning/fledging (Provisioning: Female, Protecting: Female); pre-independence (Provisioning: Female, Protecting: Female)

Barcode of Life Data Systems (BOLDS) Stats
Public Records: 0
Specimens with Barcodes: 2
Species With Barcodes: 1

Rounded Global Status Rank: G2 - Imperiled

Reasons: Fairly small range in southeastern Alaska, western British Columbia, and western Washington; population size and trends are unknown; may be threatened by habitat loss and fragmentation from clear-cut logging; existing information is inadequate for a robust assessment of current status and threats.

Year Assessed

Assessor/s

Reviewer/s

Contributor/s

Justification

History

• 1996
  Lower Risk/least concern

Due to the severe lack of information about basic life history, distribution, and population status of this species, it is on the British Columbia Red List and has a provincial rank of S2 (imperiled). British Columbia has also classified M. keenii as an identified wildlife species under the BC Provincial Forest and Range Practices Code (COSEWIC, 2003). This enables the management of the species and allows for establishment of Wildlife Habitat Areas (WHA) that defines no-disturbance perimeters around hibernacula, maternity sites, and roosting sites.

Myotis keenii is a state candidate species in Washington and is considered state sensitive in Alaska. It is not included in the IUCN Red List, CITES appendices, or the U.S. Endangered Species Act.

Temperate North American bats are now threatened by a fungal disease called “white-nose syndrome.” This disease has devastated eastern North American bat populations at hibernation sites since 2007. The fungus, Geomyces destructans, grows best in cold, humid conditions that are typical of many bat hibernacula. The fungus grows on, and in some cases invades, the bodies of hibernating bats and seems to result in disturbance from hibernation, causing a debilitating loss of important metabolic resources and mass deaths. Mortality rates at some hibernation sites have been as high as 90%. While there are currently no reports of Myotis keenii mortalities as a result of white-nose syndrome, the disease continues to expand its range in North America.

US Federal List: no special status

CITES: no special status

IUCN Red List of Threatened Species: least concern

Canada

Rounded National Status Rank: N2 - Imperiled

United States

Rounded National Status Rank: N2 - Imperiled

Population

Population Trend

Global Short Term Trend: Relatively stable to decline of 30%

Comments: Habitat quantity and quality are presumed to be declining (British Columbia Ministry of Water, Land and Air Protection 2004), but the rate of decline is unknown. Population estimates made at a British Columbia maternity colony during the 1990s indicate that it remained stable between 1991 and 2000 (COSEWIC 2003).

Degree of Threat: Medium

Comments: Logging activities and associated road building likely are reducing and fragmenting habitat; mineral extraction, forest fires, and pesticides also may be detrimental (Balcombe, 1988 COSEWIC report; British Columbia Ministry of Water, Land and Air Protection 2004). Disturbance during hibernation and while raising young is a major concern; disturbance may result from recreational activities (e.g., caving) or industrial activities (e.g., blasting for road construction) (British Columbia Ministry of Water, Land and Air Protection 2004).

Current levels of timber harvest could have a detrimental effect on the Alaska population by altering forest structure important to bats (Thomas 1988, Parker 1996, Parker et al. 1996). Bat activity is rare in clearcuts and second-growth forests of Southeast Alaska (Parker and Cook 1996, Parker et al. 1996).

As of mid-2012, this species was not known to be affected by white-nose syndrome.

Major Threats

Global Protection: Few to several (1-12) occurrences appropriately protected and managed

Comments: A maternity colony in British Columbia is protected within Gwaii Haanas National Park Reserve.

Weymer Cave and White Ridge Provincial Parks protect areas that support M. keenii hibernacula and roosting habitat. Weymer Cave has a draft management plan that identifies the need to protect the bat roosts, but also identifies recreational caving, hiking, and tourism as acceptable park activities (COSEWIC 2003).

The species undoubtedly occurs in at least a few national parks or wilderness areas in Washington and Alaska.

Needs: See British Columbia Ministry of Water, Land and Air Protection (2004) for specific protection needs and management recommendations.

Conservation Actions

Biological Research Needs: This species is known only from a limited number of museum specimens. Virtually nothing is known about its biology (van Zyll de Jong 1985). Present research needs include the following: 1. Assess habitat preferences, including roosting and feeding areas, activity patterns, and food requirements. 2. Determine if there is any seasonal movement within the population. 3. Assess whether this species hibernates, and if so, where and under what conditions. 4. Research the reproductive capacity of the species and evaluate its long-term population viability.

Bats, along with all other mammals, are capable of harboring and transmitting the rabies virus, as well as the possibility of carrying Salmonella spp., Toxoplasmosis gondii, and Ebola virus. No M. keenii individuals, and few bats, have been implicated in the transmission of these diseases.

Negative Impacts: injures humans (carries human disease); causes or carries domestic animal disease

Most bats of the family Vespertilionidae consume insects, many of which are potential pest species. Small populations of bats can consume vast quantities of insects thus controlling pest insect populations.

Positive Impacts: controls pest population