Description and Range
Western small-footed myotis are one of the smallest bats in Washington. Pelage ranges from pale tan to orange-yellow on the back and is paler (often buff or nearly white) on the undersides. The black face, ears, and flight membranes contrast strikingly with the paler overall color of the fur.
Ears are relatively long, reaching or extending beyond the snout by about 1 mm when pressed forward. The tragus is narrow and long, about half the length of the ear.
The calcar is keeled and the foot is small, about half the length of the tibia. Western small-footed myotis and California myotis are similar in appearance, but the former has paler fur that contrasts more sharply with the black wings, face, and ears, and has a longer bare area on the nose. The characteristic frequency of the echolocation call occurs in the 40 kHz range, whereas the California myotis call occurs in the 50 kHz frequency range.
Food Habits and Foraging
Western small-footed myotis feed on a variety of small flying insects, with moths, caddisflies, true bugs, and flies. Foraging begins shortly after sunset and peaks at 10-11 p.m. and again at 1-2 a.m. This species displays slow erratic flight as it forages, usually at heights from 1 m above the ground to treetop level. It is highly maneuverable and is therefore able to forage in complex habitats.
Mating happens in the fall prior to hibernation, with sperm stored by females until spring when ovulation and fertilization occur. In Washington and British Columbia, pregnancies range from May until mid-July, with births occurring from mid-June to late July depending on annual conditions. Unfavorable weather during gestation can delay births if females need to enter torpor. Litter size is almost always one. Juveniles are capable of flight about a month after birth.
This bat occurs in western North America from south-central British Columbia and the short-grass prairies of southern Alberta and Saskatchewan south to central Mexico. Western small-footed myotis are widely distributed in eastern Washington, being present in at least 19 of 20 counties, but are absent from Western Washington.
Western small-footed myotis reside in deserts, shrublands, grasslands, riparian areas, and coniferous forest, usually occurring near cliffs, rock outcrops, and talus. Elevations from 300 to 3,300 m are used. In Washington, dry open habitats appear to be most frequently occupied, especially those with rock outcrops and cliffs.
Most captures at Hanford and probably at the Yakima Training Center were in riparian trees or along creeks, with others taken in gullies, a planted tree, and a building. The species also inhabits mixed conifer forest and ponderosa pine forest up to about 1,400 m.
Maternity roosts and other day roosts of both sexes occur in small sheltered crevices in rock faces and cliffs, among boulders in talus, beneath the bark of trees, in buildings, caves, and mines, and under bridges. Average temperatures in roosts range from 27-29ºC (81- 84ºF). Individuals roost alone or in small groups. Summer day roosts of males and non-reproductive females are separate from nurseries. No maternity sites have yet been found in Washington.
Night roosting occurs in caves, mine entrances, buildings, and bridges. Some day roosts serve as night roosts. Night roosts are sometimes shared with other species, such as big brown bats and Townsend’s big-eared bats.
In Oregon, British Columbia, and elsewhere, hibernacula occur in tight crevices of caves, abandoned mines, and rarely in buildings, with ambient temperatures typically ranging from –3º to 9ºC (27-48ºF) and relative humidity from 24% to 66%. Nothing is known about the locations or characteristics of wintering sites in Washington. This species usually hibernates in small numbers per site, either singly or in clusters of two or three individuals.
- Although information is sparse, it appears that cliffs, rock outcrops, talus slopes, caves, and mines are important roost sites; efforts should be made to protect roosts in these types of sites whenever possible.
- Conversion of shrub-steppe and grassland and degradation of riparian habitats near cliff faces should be avoided because of the potential to reduce foraging habitat.
- Before pesticide spraying projects, surveys to identify bat roosting and foraging areas should be conducted to avoid spraying of important habitats.
For some people bats don't present a problem. For others, bats can be a worry, especially when they become unwanted guests in an attic, inside a wall of a home, or inside the home itself.
Unlike rodents, bats only have small teeth for eating insects, so they do not gnaw holes in walls, shred material for nests, chew electrical wiring, or cause structural damage to buildings. Damage caused by bats is usually minimal, but they can be noisy and alarming, and the smell of bats and their droppings can be offensive. It is possible to learn to coexist with bats, and to benefit from their presence. Learn more on our Living with Wildlife: Bats webpage.