Myotis ciliolabrum
(Western Small-footed Myotis )

Order: Chiroptera
Order Description: Bats
Family Description:

The upper fur is brownish and tends to have an yellowish-orange cast in Idaho. The blackish ears, containing a short pointed tragus Click word for definition, are rounded at the margin and do not extend forward beyond the muzzle. A distinct black mask exists across the muzzle and face to the ears. The calcar Click word for definitionis keeled and the foot small.

Southern British Columbia, Alberta and Saskatchewan along the western edge of the Dakotas, Nebraska, Kansas, Oklahoma, and northern Texas into central Mexico, then west to northern Baja California and along the eastern half of the Pacific Coast states of California, Oregon and Washington.

This bat has been found in a range of habitats in Idaho and is likely one of the more common bats. It appears to be more abundant in southern Idaho in lava-tube caves where it hibernates in cracks and crevices. In other states, it occurs in montane and coniferous forests and is found under exfoliating bark, in cracks and crevices in rocks, and in old buildings.

Found in arid habitat associated with cliffs and talus slopes. In Texas, principally found in mountainous, wooded areas, with a few found in grassland and shrub steppe habitats. In Canada, inhabits arid, short-grass prairies with clay buttes and steep riverbanks.

Western small-footed myotis eat small insects including moths, flies, true bugs and ants. The food taken may vary with the diet of similar-sized sympatric species, especially California myotis. Subdivision of forage areas to rocky bluffs occurs when this species occurs sympatrically with California myotis.

(Oregon study identified Lepidoptera Click word for definition, Hemiptera Click word for definition, and Diptera Click word for definition; British Columbia study found Trichoptera Click word for definition).

The classification of this bat has changed from Myotis subulatus and later M. leibii. It may also be incorrectly identified as M. californicus, a species which has a more globular cranium, tri-colored fur and is usually found in dryer areas. Individuals do not cluster together and hibernation appears to be extended for a longer period of time in western small-footed myotis than California myotis.

Hibernates Click word for definition in caves and mines in winter (one of the last bats to begin hibernation Click word for definition). In Idaho, known to winter in lava-tube caves in southern part of state. Roosts in summer in rock crevices, under boulders, beneath loose bark, or in buildings. During warmer months, leaves daytime roost Click word for definitionshortly after sunset. Forages along cliffs and rocky slopes at heights of 1-3 m. Foraging activity peaks between 2200-2300 hr and 0100-0200 hr. Species is sympatric Click word for definitionwith California myotis; appears to coexist by spatial partitioning of available food source.

Swarming is known to occur at high elevations in September. Mating takes place prior to and potentially after hibernation. Sperm are stored until spring ovulation occurs. A single pup is born. Nursery colonies are likely small but little is known about group size in this species in Idaho.

Little information is available. Observations of pregnant and lactating Click word for definitionfemales indicate that parturition Click word for definitionoccurs from late May or June through early July. In U.S., females usually produce 1 young (sometimes 2 at more southern latitudes). Maternity colonies are small.

Status: Unprotected nongame species
Global Rank: G5
State Rank: S4

Important State References:
Genter, D.L. 1986. Wintering bats of the upper Snake River plain: occurrence in lava-tube caves. Great Basin Natur. 46:241-244.

Information written by Barry Keller,© 2000
Map image provided by
Stephen Burton,© 2000
Design by Ean Harker©1999, 2000.