Geographic Range
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.
Habitat
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.
- Habitat Regions
- temperate
- terrestrial
- Terrestrial Biomes
- forest
Physical Description
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.
- Other Physical Features
- endothermic
- heterothermic
- bilateral symmetry
- Sexual Dimorphism
- sexes alike
Reproduction
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.
- Key Reproductive Features
- iteroparous
- seasonal breeding
- gonochoric/gonochoristic/dioecious (sexes separate)
- sexual
- viviparous
- sperm-storing
- delayed fertilization
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
-
provisioning
-
pre-weaning/fledging
-
provisioning
- female
-
protecting
- female
-
provisioning
-
pre-independence
-
provisioning
- female
-
protecting
- female
-
provisioning
Lifespan/Longevity
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.
Behavior
M. keenii
appears, by all accounts, to be a social creature. Studied maternity roosts have
been approximated at 30 to 40 females, and hibernacula have similarly been documented
as the residence for large colonies of bats, even incorporating other species of bat.
They are nocturnal, but may be active at dusk and dawn.
Myotis keenii
hibernates during the winter and becomes torpid during daytime roosting.
- Key Behaviors
- arboreal
- flies
- nocturnal
- crepuscular
- motile
- migratory
- hibernation
- daily torpor
- social
Home Range
This species of bat tends to stay relatively close to favored roosting sites and from
the limited studies and accounts involving
M. keenii
the estimated daily travels are less than 1 km. Evidence that these bats return
to specific foraging areas year after year has also been documented although their
specific roosting and foraging range sizes have not been determined. It has also
been suggested that
M. keenii
may make short migrations between summer ranges and hibernacula.
Communication and Perception
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.
- Perception Channels
- visual
- tactile
- acoustic
- ultrasound
- echolocation
- chemical
Food Habits
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.
- Primary Diet
- carnivore
- Animal Foods
- insects
- terrestrial non-insect arthropods
Predation
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.
Ecosystem Roles
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.
Economic Importance for Humans: Positive
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
Economic Importance for Humans: Negative
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
Conservation Status
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.
Other Comments
Myotis keenii
was previously considered conspecific with
Myotis septentrionalis
, which was recognized as a distinct species by van Zyll de Jong in 1979. It is now
understood that
M. keenii
is closely related to
M. evotis
and
M. thysanodes
, and is only distantly related to
M. septentrionalis
>
Additional Links
Contributors
Joe Filla (author), University of Alaska Fairbanks, Link E. Olson (instructor), University of Alaska Fairbanks, Tanya Dewey (editor), Animal Diversity Web.
- Nearctic
-
living in the Nearctic biogeographic province, the northern part of the New World. This includes Greenland, the Canadian Arctic islands, and all of the North American as far south as the highlands of central Mexico.
- native range
-
the area in which the animal is naturally found, the region in which it is endemic.
- temperate
-
that region of the Earth between 23.5 degrees North and 60 degrees North (between the Tropic of Cancer and the Arctic Circle) and between 23.5 degrees South and 60 degrees South (between the Tropic of Capricorn and the Antarctic Circle).
- terrestrial
-
Living on the ground.
- forest
-
forest biomes are dominated by trees, otherwise forest biomes can vary widely in amount of precipitation and seasonality.
- suburban
-
living in residential areas on the outskirts of large cities or towns.
- riparian
-
Referring to something living or located adjacent to a waterbody (usually, but not always, a river or stream).
- estuarine
-
an area where a freshwater river meets the ocean and tidal influences result in fluctuations in salinity.
- endothermic
-
animals that use metabolically generated heat to regulate body temperature independently of ambient temperature. Endothermy is a synapomorphy of the Mammalia, although it may have arisen in a (now extinct) synapsid ancestor; the fossil record does not distinguish these possibilities. Convergent in birds.
- heterothermic
-
having a body temperature that fluctuates with that of the immediate environment; having no mechanism or a poorly developed mechanism for regulating internal body temperature.
- bilateral symmetry
-
having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends. Synapomorphy of the Bilateria.
- iteroparous
-
offspring are produced in more than one group (litters, clutches, etc.) and across multiple seasons (or other periods hospitable to reproduction). Iteroparous animals must, by definition, survive over multiple seasons (or periodic condition changes).
- seasonal breeding
-
breeding is confined to a particular season
- sexual
-
reproduction that includes combining the genetic contribution of two individuals, a male and a female
- viviparous
-
reproduction in which fertilization and development take place within the female body and the developing embryo derives nourishment from the female.
- sperm-storing
-
mature spermatozoa are stored by females following copulation. Male sperm storage also occurs, as sperm are retained in the male epididymes (in mammals) for a period that can, in some cases, extend over several weeks or more, but here we use the term to refer only to sperm storage by females.
- delayed fertilization
-
a substantial delay (longer than the minimum time required for sperm to travel to the egg) takes place between copulation and fertilization, used to describe female sperm storage.
- altricial
-
young are born in a relatively underdeveloped state; they are unable to feed or care for themselves or locomote independently for a period of time after birth/hatching. In birds, naked and helpless after hatching.
- arboreal
-
Referring to an animal that lives in trees; tree-climbing.
- nocturnal
-
active during the night
- crepuscular
-
active at dawn and dusk
- motile
-
having the capacity to move from one place to another.
- migratory
-
makes seasonal movements between breeding and wintering grounds
- hibernation
-
the state that some animals enter during winter in which normal physiological processes are significantly reduced, thus lowering the animal's energy requirements. The act or condition of passing winter in a torpid or resting state, typically involving the abandonment of homoiothermy in mammals.
- social
-
associates with others of its species; forms social groups.
- acoustic
-
uses sound to communicate
- chemical
-
uses smells or other chemicals to communicate
- visual
-
uses sight to communicate
- tactile
-
uses touch to communicate
- acoustic
-
uses sound to communicate
- ultrasound
-
uses sound above the range of human hearing for either navigation or communication or both
- echolocation
-
The process by which an animal locates itself with respect to other animals and objects by emitting sound waves and sensing the pattern of the reflected sound waves.
- chemical
-
uses smells or other chemicals to communicate
- causes or carries domestic animal disease
-
either directly causes, or indirectly transmits, a disease to a domestic animal
- carnivore
-
an animal that mainly eats meat
- insectivore
-
An animal that eats mainly insects or spiders.
References
COSEWIC, 2003. "COSEWIC assessment and update status report on Keen's long-eared bat Myotis keenii in Canada." (On-line pdf). Government of Canada: Species At Risk Act Public Registry. Accessed November 24, 2004 at http://www.sararegistry.gc.ca/virtual_sara/files/cosewic/sr_keens_longeared_bat_e.pdf .
Chatwin, T. 2004. "Keen's Long-eared Myotis" (On-line pdf). British Columbia Ministry of Water, Land & Air Protection. Accessed November 24, 2004 at http://wlapwww.gov.bc.ca/wld/identified/documents/Mammals/m_keensmyotis.pdf .
Cryan, P. 2010. "White-nose syndrome threatens the survival of hibernating bats in North America" (On-line). U.S. Geological Survey, Fort Collins Science Center. Accessed September 16, 2010 at http://www.fort.usgs.gov/WNS/ .
Government of British Columbia, 2003. "BC Species and Ecosystems Explorer" (On-line). Accessed December 09, 2004 at http://srmapps.gov.bc.ca/apps/eswp/ .
Hall, R. 1981. Mammals of North America, 2nd Ed., Vol. 1 . New York, New York: John Wiley & Sons, Inc..
Lewis, S. 2000. Roosting and Hibernal Ecology of Bats in Southeast Alaska's Karstlands. The Alaskan Caver , Vol. 20, No. 4: 1 to 6.
Ministry of Environment, Lands and Parks Resources Inventory Branch, 1998. "Inventory Methods for Bats" (On-line pdf).
Inventory Methods for Bats : Standards for Components of British Columbia's Biodiversity No. 20. Accessed November 24, 2004 at http://srmwww.gov.bc.ca/risc/pubs/tebiodiv/bats/assets/bats.pdf .
Nagorsen, D., R. Brigham. 1993. The Bats of British Columbia . Vancouver, BC: UBC Press, University of British Columbia.
National Park Service, Wildlife Health Center, 2010. "White-nose syndrome" (On-line). National Park Service, Wildlife Health. Accessed September 16, 2010 at http://www.nature.nps.gov/biology/wildlifehealth/White_Nose_Syndrome.cfm .
Parker, D., B. Lawhead, J. Cook. 1997. Distributional Limits of Bats in Alaska. Arctic , Vol. 50, No. 3: 256-265.
Tuttle, M., D. Stevenson. 1982. Growth and Survival of Bats. Pp. 105 to 149 in Ecology of Bats . New York, USA: Plenum Press.
van Zyll de Jong, C. 1985. Handbook of Canadian Mammals, Vol. 2 . Ottawa, Canada: National Museums of Canada.
State of Alaska, Department of Fish & Game. Bats in Alaska. Vol. 18, No. 4 (July-Aug. 1986) p. 20. Anchorage, Alaska: State of Alaska, Department of Fish & Game. 1986.
State of Alaska, Section of Epidemiology. Bats in Alaska. Bulletin No. 16. Anchorage, Alaska: State of Alaska, Section of Epidemiology. 2001. Accessed November 29, 2004 at http://www.epi.hss.state.ak.us/bulletins/docs/b2001_16.htm .