Western Long-eared bat (Myotis evotis)

Physical description

Western long-eared myotis are small bats and one of the mid-sized species of Myotis in Washington. In the two subspecies present in Washington, the fur on the upperparts is yellowish brown in M. e. evotis and darker brown to nearly black in M. e. pacificus. Distinct but poorly defined blackish-brown patches may be evident on the shoulders. Pelage color on the undersides is relatively light. Small hairs along the edge of the tail membrane form an inconspicuous fringe that is less distinct than in fringed myotis. Ears and flight membranes are blackish and contrast with the paler fur.

Ears are relatively long, extending 5 mm or more beyond the nose when pressed forward. The tragus is long and slender with a small lobe at its base. The foot is relatively small, less than half the length of the tibia, and the calcar lacks a distinct keel. The western long-eared myotis is one of three physically similar long-eared Myotis species in Washington.

Food Habits and Foraging
Moths are important food items for western long-eared myotis, but beetles, flies, spiders, true bugs, and other insects are also eaten. Moths, caddisflies, and termites were the main foods in a small sample from Joint Base Lewis-McChord, Washington.

This species displays flexible feeding behavior, catching prey either by aerial hawking or gleaning from vegetation or the ground while hovering. These bats are considered slow fliers with good maneuverability. Western long-eared myotis emerge from day roosts near dusk to forage and return about two hours before sunrise. Bats forage for about half of the night, averaging four activity periods that are interspersed with short periods of inactivity. Foraging occurs in a variety of forest types, along forest edges, and over open meadows, but riparian areas and other habitats near water appear to be especially preferred.

Reproduction
Mating occurs in fall or early winter, presumably after females and young join males at swarming sites outside hibernacula, with ovulation and fertilization delayed until spring. In eastern Washington, pregnancies have been noted from June until late July. Births have been reported in mid-July in western Washington.  Females give birth to one young per year. Young begin to fly about a month after birth, with flying young first observed on Aug. 2 in Eastern Washington.

Geographic range

Western long-eared myotis occur in western North America from central British Columbia and southern Saskatchewan to central New Mexico and the Baja peninsula. Records occur for most of Washington’s counties, but are missing from the south-central Columbia Basin. Some records from western Washington may be erroneous because of confusion with Keen’s myotis.

Western long-eared myotis are most commonly associated with conifer forests ranging from drier ponderosa pine to humid coastal and montane forests. Non-forested habitats are also used, including shrub steppe, chaparral, and agricultural lands, if suitable roosting sites, water sources, and riparian habitats are available. Presence of broken rock outcroppings and snags appears to be more important in determining habitat suitability than vegetation type. The species occurs from sea level to 3,100 m. Many of the habitats noted here are occupied in Washington, including subalpine forests up to 1,640 m in elevation.

Elevation appears to limit the distribution of reproductive females in Washington. One study found proportionately fewer adult females at higher (1,000-1,400 m) elevations compared to lower (760-1,260 m) elevations along the east slope of the Cascades in Kittitas and Yakima counties.

Roosting
Day roosts are located beneath loose bark on trees, snags, stumps, and downed logs, as well as in buildings, crevices in ground-level rocks and cliffs, tree cavities, caves, and mines.

Maternity colonies typically contain 4-30 females, whereas males and non-reproductive females live singly or in small groups, occasionally occupying the same site as a maternity. Conifer snags used as maternity roosts are usually large in diameter and height, and in intermediate stages of decay with exfoliating bark present. Such roosts often occur in canopy gaps or near forest margins, and are located mainly in upslope areas near water. Stumps in clearcuts are also important as day roosts for reproductive and non-reproductive females and males in areas, but are usually occupied only 5-10 years before overtopping vegetation prevents access. Stumps and downed logs may be mostly used when snags are unavailable.

At Turnbull National Wildlife Refuge in eastern Washington, maternity colonies occur almost entirely in crevices in small rock formations. Maternity colonies have also been noted in an attic in Clallam County and in mines in Ferry and Stevens counties. Females and males switch day roosts once every 1-4 days. Ground roosts are usually clumped within a relatively small area.

Caves, mines, bridges, and outbuildings are used as night roosts. In the Columbia River Gorge, caves serve as night roosts, but not as day roosts.

Hibernation
Caves, mines, and possibly buildings serve as hibernacula. In Washington, single individuals have been found hibernating in a lava tube in Skamania County and a cave in Klickitat County. Whether this species hibernates in trees is unknown. Hibernation begins from about late September to late October.