Myotis evotis

"With its long, luxurious fur, which can range in color from dark brown to pale yellow, and its large, coal-black ears, the long-eared myotis is a striking animal. Long-eared myotis prefer roosting in rock outcroppings and dead trees. They feed on a variety of insects, and are often seen hunting in dense vegetation or over small bodies of water. They seem to prefer moths and beetles, and it appears these bats ""turn off"" their echolocation to listen for insects, which they can pluck from trunks and branches by hovering momentarily. Like many bats, but unlike most other small mammals, they have a long life span. Individuals have been known to live for 22 years, although the average is much shorter."

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Global Range: (>2,500,000 square km (greater than 1,000,000 square miles)) Range includes western North America, from central British Columbia, southern Alberta, and southern Saskatchewan south along the Pacific Coast to Baja California, east through Montana and Idaho to the western Dakotas, and from Nevada, Utah, Wyoming and Colorado to New Mexico and Arizona (Manning and Jones 1989, Adams 2003, Reid 2006). Elevational range extends from near sea level along the Pacific Coast to around 2,900 meters in Utah and Wyoming (Manning and Jones 1989, Adams 2003).

Southern British Columbia, Southern Alberta, Southern Saskatchewan (Canada) to New Mexico (USA) and Baja California (Mexico) (Simmons 2005).

The geographic range of Myotis evotis, or long-eared Myotis, includes much of the western United States from the Pacific Coast to the front range of the Rocky Mountains and western Dakotas. The geographic range reaches up into the lower Canadian provinces of British Columbia, Saskatchewan and Alberta and south into central New Mexico and Arizona. Although widespread, M. evotis is not particularly common throughout the majority of its range.

Two subspecies exist: M. e. evotis of the mountains and high plains of the western U.S. and soutwestern Canada, and M. e. pacificus of coastal regions of the Pacific Northwest.

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 evotis is dull to pale brown or straw colored with black ears and membranes. The ears, ranging between 19 and 22 mm in length, are the longest of any North American Myotis. The tragus is long and slender. The calcar has little to no keel. The auditory bullae are relatively large compared to other Myotis bats. The dentition is 2/3, 1/1, 3/3, 3/3. Total length, observed in a population of South Dakota bats, ranges from 87 to 100 mm.

Myotis evotis exhibits very little sexual dimorphism, with females being a bit larger than males, though only showing slight differences of length in ear and fifth metatarsal.

There is evidence of geographic variation in size. Specimens of M. evotis from British Columbia have larger skulls than those from Washington; Washington bats are more similar to those found further inland.

Myotis evotis morphologically overlaps with Myotis keenii. The two are sympatric in coastal areas of British Columbia and Washington. The geographic variation of M. evotis has made it difficult to distinguish between the two, and in some collections, identification errors have been made. No external features have been identified that clearly seperate the two species. The skull of M. evotis contains a longer tooth row than that of M. keenii. The distance from the last upper pre-molar to the last upper molar is greater than 4.2 mm. Another Myotis species that is difficult to distiguish is Myotis septentrionalis, commonly known as northern long-eared myotis. Longer tooth row and longer ears help distinguish M. evotis.

Range mass: 5 to 8 g.

Range length: 87 to 100 mm.

Average wingspan: 250 mm.

Sexual Dimorphism: sexes alike; female larger

Length: 10 cm

Length:
Range: 87-100 mm

Weight:
Range: 5-8 g

Habitat and Ecology

Systems

• Terrestrial

Myotis evotis is found in a wide range of habitats, but is most commonly found in mixed coniferous forests, from humid coastal areas to montane forests. Elevation ranges from sea level on the Pacific Coast to 2,830 meters in the mountains of Wyoming. The habitat of M. evotis is largely dependent on what the bats use for their day roosts. In southern British Columbia, long-eared myotis roost in tree cavities in dense forests. In adapting to forest management in certain areas of British Columbia, they have recently been found to roost in the stumps of clear-cut stands. Long-eared myotis prefer the stumps of ponderosa pine and lodgepole pine in these areas. In the large uninterrupted forests of the Pacific Northwest, M. evotis uses large snags for day roosts. These bats usually prefer snags that reach high into or above the forest canopy. In the badlands of the South Sasketchawan River Valley in Alberta, M. evotis are mostly found roosting in the crevices of sandstone boulders. Other places which function as day roosts are abandoned buildings, cracks in the ground, caves, mines, and loose bark on living and dead trees.

Range elevation: 0 to 2,830 m.

Habitat Regions: temperate ; terrestrial

Terrestrial Biomes: forest ; rainforest ; scrub forest ; mountains

Habitat Type: Terrestrial

Comments: Mostly forested areas, especially those with broken rock outcrops; also shrubland, over meadows near tall timber, along wooded streams, over reservoirs. Often roosts in buildings, also in hollow trees, mines, caves, fissures, etc. Small maternity colonies of 12-30 individuals have been found in buildings in British Columbia, and a group of adults and young were found in an uninhabited ranch house in Colorado (Barbour and Davis 1969). In northeastern Washington, roosts of reproductive females were in crevices in small basalt rock formations (Rancourt et al. 2005). See Vonhof and Barclay (1996) for information on characterisitcs of roost trees in British Columbia.

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.

The winter range is not known. This species is probably migratory (Banfield 1974).

Myotis evotis is insectivorous. These bats emerge to feed approximately one hour after dark. They prey mainly on moths, but their diet also includes beetles, flies, and spiders. They can take prey from the air (hawk) as well as from surfaces (glean). The ability to incorporate both methods of foraging requires a pattern of flight that is slow and methodical, and which requires more energy compared to the flight patterns of faster-flying bats. Because the methodical flight requires more energy, these bats are forced to forage for prolonged periods. The dual method of foraging also allows for foraging and reproducing in less hospitable climates, due to the access to more than one source of prey. Females can breed in high cool climates, where there is decreased availability of flying insects. Myotis evotis can forage for longer periods because it does not rely on a precise heightened insect activity period. Aerially foraging bats focus on peak times of insect abundance, dusk and dawn. Myotis evotis can forage throughout the night, and not rely on peak foraging windows.

Myotis evotis studied in a montane grassland area was found to feed on the following insect families: Lepidoptera, Coleoptera, Diptera, Neuroptera, Hymenoptera, Hemiptera and Homoptera. Considered temporal opportunists, M. evotis certainly feed to a large extent on moths. Moths are both gleaned from surfaces or taken in the air and both techniques require a unique method of echolocation. Myotis evotis adjusts its echolocation method to fit the acoustical limitation of each foraging situation. For example, when gleaning insects off a surface, the bat has to deal with interference clutter (surfaces reflecting off with more energy than the prey located on that surface). Myotis evotis uses lower amplitude calls when gleaning, and stops calls just before striking, when it actually uses sounds made by the prey to help coordinate its attack. While taking insects from the air, M. evotis uses techniques such as a feeding buzz, used to constantly monitor the environment, even when enacting the final attack on a prey.

Although once considered an active prey specialist, M.evotis is actually a passive prey specialist. The selectivity for moths in the diet of this species is due to a biased sensory system that has especially acute ability to perceive prey-generated sounds. The short duration, broad-band, frequency modulated echolocation calls used by M. evotis are certainly useful for the gleaning of prey off surfaces; however, evidence indicates that they can glean insects from surfaces without use of echolocation. Myotis evotis has extremely sensitive low frequency hearing and can use prey-generated sounds to detect prey without the use of echolocation. This was revealed by an experiment with a hidden moth where echolocation could not confirm the location of prey, yet the bat was still accurate in attacking. The advantages of gleaners using a variety of sensory cues are many. Because tympanate moths have evolved a sensitivity to and avoidance of echolocation calls, M. evotis, which can locate these moths without use of echolocation calls, are more likely to take such moths than are less adept species of bats.

Animal Foods: insects; terrestrial non-insect arthropods

Primary Diet: carnivore (Insectivore )

Comments: Insectivorous. Forages over water or among trees. Usually feeds by picking prey from surface of foliage, tree trunks, rocks, or ground; may fly slowly around shrub searching for emerging moths or perhaps nonflying prey. See Manning and Jones (1989).

As with all small mammals, the amount of energy M. evotis requires to maintain metabolic function results in considerable impact on ecosystems. With M. evotis needing more energy than most, due to its unique energy-intensive flying patterns, it forages for a longer time and is perhaps more successful at taking prey. Wide distribution is testament to the relative success of M. evotis . This species clearly has a large impact on populations of insects upon which it preys.

In populations of M. evotis living in a Pacific Northwest forest of clear-cut stumps, possible predators include chipmunks (Eutamias amoenus) and bears (Ursus americanus), in addition to other common small mammal predators. To avoid these predators, M. evotis switches roosts frequently. Switching roosts limits the amount of scent that can build up from constant use. In tree bark roosts, the bats often were found face-up at the bottom of the cavity and were well camouflaged.

In British Columbia, a yellow-bellied racer, Coluber mormon, was established as a predator.

Known Predators:

• yellow-bellied racers (Coluber mormon)

Anti-predator Adaptations: cryptic

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

Estimated Number of Occurrences: 81 to >300

Comments: This species is represented by a large number of occurrences (subpopulations). As evidence of this, Verts and Carraway (1998) mapped more than 100 collection sites in Oregon, Hoffmeister (1986) mapped 52 localities in Arizona, and Nagorsen and Brigham (1993) mapped approximately 49 collection sites in British Columbia.

10,000 to >1,000,000 individuals

Comments: Total adult population size is unknown but presumably exceeds 10,000. According to Barbour and Davis (1969), this bat is never abundant but regularly distributed. In Arizona, it appears to be widespread and occurs regularly, if not always commonly, in appropriate habitat (Arizona Game and Fish Department 1993). It is considered a widespread but relatively uncommon species in Montana and Oregon (Manning and Jones 1989, Eleanor Gaines, pers. comm., 1998). Tuttle and Taylor (1994) stated that mine colonies are usually in the dozens and mines can be used year round. According to the Arizona Game and Fish Department (1997), females form small maternity colonies in the summer. Roosting and maternity colonies can range from 1 to 30 or 5 to 30 individuals, respectively (New Mexico Department of Game and Fish 1997, Nagorsen and Brigham 1993).Colony size is usually 12-30 individuals (Adams 2003).

Widespread, not uncommon, but little is known about habits. It has been found foraging with M. VOLANS, EPTESICUS FUSCUS, LASIONYCTERIS NOCTIVAGANS, and L. CINEREUS.

Echolocation is essential to M. evotis, as it is through this means that these bats are able to capture their prey. Echolocation can be used in different ways when capturing prey. Changing calls or ceasing calls are both options for capturing prey in different situations. Although echolocation is the main means of capturing prey when “hawking” insects from the air, M. evotis will cease calling and use prey-generated sounds to guide the attack. This ability has many ramifications in feeding behavior, habitat range, and prey selection for M. evotis. Tympanate moths are a primary food source, and these foraging tactics make M. evotis all the more effective at capturing prey in the air or off a surface.

Other forms of communication or uses for echolocation for M. evotis are not completely known. Other echolocating bats have been found to actually use echolocation as a means of communication with each other. Myotis lucifugus was observed to use echolocation in identifying roosts, mating sites, hibernation sites and feeding areas. Other bats have been found to react aggressively to echolocation calls of conspecifics thus maintaining spacing between individuals. Echolocation can also facilitate mother-young recognition.

Although reports in the literature are absent, we may infer that mothers and their young use some tactile communication. It is also likely that this type of communication occurs between mates. Chemical communication has not been reported for these animals.

Communication Channels: visual ; tactile ; acoustic

Perception Channels: visual ; acoustic ; ultrasound ; echolocation

Comments: Reportedly emerges late in evening to feed, though other authors report earlier emergence (see Manning and Jones 1989).

The lifespan of these animals has been reported as a maximum of 22 years in the wild. It is unlikely that most individuals live that long.

Range lifespan
Status: wild: 22 (high) years.

Average lifespan
Sex: male
Status: wild: 2.2 years.

Maximum longevity: 22 years (wild)

Mating systems for M. evotis are relatively unkown. Although some similarities to other Myotis species can be inferred, actual data for M. evotis do not exist.

Most species of the genus for which there are data appear to be polygynandrous. Myotis myotis mating involves the females from different colonies traveling several miles to male roost sites. Little is observed in male behavior in attracting females. Reproduction in Myotis lucifugus involves copulation and insemination prior to hibernation. The sperm are then stored in the uterus until spring.

Mating System: polygynandrous (promiscuous)

Records of M. evotis reproduction are very incomplete. Most data are either based upon anecdotal accounts or museum specimens. The young are born in late spring/early summer. Lactating females have been collected in July and August. Myotis evotis reproduces once per year, and females may form maternity colonies of 5 to 30 individuals in the summer (colonies may contain a few males), or they can remain solitary.

The young are born naked with sharp milk teeth. Size of the neonates ranges around 7 to 8 cm, with a weight of around 1 to 1.5 grams.

A study of reproducing females in Alberta produced some interesting data on roost differences between pregnant and lactating females. Pregnant females roost in horizontal rock crevices, which are closer to the surface, warm rapidly, and have a higher mean daytime temperature. Pregnant females can maintain a higher body temperature at a lower cost to them by roosting in a warmer place. The horizontal surface rock crevices cool very quickly, however the bats spend these cool hours foraging. When they return to the cold roost, they drop into torpor until passively warmed by the ambient temperature, thus saving more energy for use towards fetal development.

Females who had given birth to young used deeper vertical rock crevices, which maintain a higher overall temperature. Juveniles that are left in the roost while the mother forages can not effectively maintain their high body temperatures. Vertical rock crevices fluctuate less in temperature, keeping the juveniles warmer and more stable.

Breeding interval: Myotis evotis breeds once per year.

Breeding season: Mating occurs in autumn or early winter.

Range number of offspring: 1 to 1.

Range gestation period: 40 to 60 days.

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

Average birth mass: 1.22 g.

Average number of offspring: 1.

Parental investment is not well known for M. evotis. Lactating females choose a roost that is suitable for the young, which can not yet thermoregulate. Maternity roosts are often made up of several to several dozen individuals. The roost differs from that chosen while pregnant. Length of lactation and parental care has not been reported. The role of males in parental care has not been reported, but, as in most bats, it is likely that parental care is provided solely by the female, who nurses, protects, and grooms the altricial offspring.

Parental Investment: no parental involvement; altricial ; pre-fertilization (Protecting: Female); pre-hatching/birth (Provisioning: Female, Protecting: Female); pre-weaning/fledging (Provisioning: Female, Protecting: Female); pre-independence (Provisioning: Female)

Litter size is 1. Births have been recorded in mid-July in western Washington. Young and lactating females were recorded in late July in New Mexico. Female and newborn young were recorded in late June in California. Male young-of-year about adult size were observed in early August in South Dakota.

Barcode of Life Data Systems (BOLDS) Stats
Public Records: 0
Specimens with Barcodes: 3
Species With Barcodes: 1

Canada

Rounded National Status Rank: N4 - Apparently Secure

United States

Rounded National Status Rank: N5 - Secure

Rounded Global Status Rank: G5 - Secure

Reasons: Widespread distribution in western North America; many occurrences; apparently occurs regularly in low numbers across range; through much of range considered moderately to not very threatened.

Year Assessed

Assessor/s

Reviewer/s

Contributor/s

Justification

History

• 1996
  Lower Risk/least concern

Myotis evotis is a previous candidate 2 species under the U.S. Endangered Species Act. It has no formal federal status, but is recognized as state sensitive in many areas of the western U.S.

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 evotis 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

Global Short Term Trend: Relatively stable (=10% change)

Comments: Trend over the past 10 years or three generations is uncertain, but distribution and abundance probably are relatively stable.

Population

Population Trend

Degree of Threat: BC

Comments: Overall, no major threats are known.

Locally, maternity colonies, hibernacula, and roosts are vulnerable to disturbance and destruction (Doug Backlund, pers. comm., 1998, New Mexico Department of Game and Fish 1997). Special precautions should be taken when mine and cave surveys are conducted during breeding periods and winter hibernation. Disturbance of breeding colonies can cause young to lose their grasp and fall to their death. Disturbance during hibernation can cause bats to use up stored fat reserves and starve to death.

Cutting of large snags is of particular concern in Arizona. Roosts under exfoliating bark may be relatively short-lived resources (New Mexico Department of Game and Fish 1997). These bats may be affected by the closure of abandoned (unsurveyed) mines, recreational caving, some forestry management practices, and activities (such as highway construction, water impoundments, blasting of cliffs for avalanche control) that impact cliff faces or rock outcrops (Western Bat Working Group 1998). They also may be negatively affected by regional insecticide applications (John Fleckenstein, pers. comm., 1998).

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

Major Threats

Global Protection: Many to very many (13 to >40) occurrences appropriately protected and managed

Comments: Many occurrences are in protected areas.

Conservation Actions

M. evotis is a known carrier of rabies.

Negative Impacts: injures humans (bites or stings, causes disease in humans , carries human disease)

As an insectivore, M. evotis has some effect on insect pest control.

Positive Impacts: controls pest population