Myotis thysanodes
(Fringed Myotis)

Order: Chiroptera
Order Description: Bats
Family Description:

The dorsal upper fur is often reddish-brown, the rounded ears long (3/4 inch = 16-20 mm), the tragus Click word for definitionlong and pointed and the tail membrane distinctly fringed. Occasionally, this species might be confused with Myotis evotis as a result of individuals with a very few hairs along the margin of the tail membrane.

From south-central British Columbia, south through western U.S. to portions of southern Mexico. Disjunct population occurs in Black Hills of Wyoming and South Dakota. Winter range is not well known; Idaho range is only known from 2 locales, but distribution is probably much greater.

Western North America from southern British Columbia east to South Dakota, south into Mexico and west to California. This species, uncommon in Idaho, has been collected or observed in Boise, Butte, Clearwater, Latta, Nez Perce, Owyhee, and Shoshone Counties.

Desert, oak and pinon-juniper woodlands (where most common) and coniferous or mixed deciduous Click word for definitionforest usually in mid elevations. The wing membranes and food habits suggests this bat has a foraging strategy permitting gleaning of insects from vegetative surfaces. Individuals may change roost Click word for definitionsites as a result of disturbance.

Found in desert, grassland, and woodland habitats, primarily at middle elevations of 1200-2150 m. Has been recorded at 2850 m in spruce/fir forests in New Mexico, and at low elevations along Pacific Coast.

Insectivorous Click word for definition; beetles and moths are common prey item.

This species occurs in a large number of roosting conditions including snags, hollows in trees, buildings, mines, rock crevices, and bridges. Females and males separate during pup rearing. On the basis of studies completed outside of Idaho, this species appears to be rare, a condition that made the fringed myotis a former Category 2 candidate species.

Hibernates Click word for definition/aestivates Click word for definition. Known to be active from April-September. Roosts in caves, mines, rock crevices, buildings, and other protected sites. Often forages close to vegetative canopy. Wings have high puncture strength, which is characteristic of bats that forage by gleaning from ground or near thick or thorny vegetation. In Idaho, found with many other species, including long-eared myotis, long-legged myotis, and California myotis; known to roost communally, but never closer than 3 m to other bat species. Easily disturbed by human presence. Known to thermoregulate. Ecology of this species is poorly known, particularly in winter.

Reproduction begins upon break-up of maternity colonies which appear to be located in cool wet conditions. Ovulation Click word for definition, and implantation Click word for definition occurs from April to May. Fifty to 60 days later a single young is born in late June or early July.

Apparently little variation exists in timing of reproduction throughout range. In northeastern New Mexico, mating occurs in fall; ovulation Click word for definition, fertilization Click word for definition, and implantation Click word for definitionoccur from late April to mid-May. Gestation Click word for definitionlasts 50-60 days; births occur in late June to mid-July. Female produces 1 young. Young can fly at 16-17 days. Maternal colony sizes may reach several hundred individuals; colonies begin to disperse in October.

Status: Protected nongame species
Global Rank: G5
State Rank: S1

Important State References:
Keller, B.L. 1999. Thermal characteristics of lava caves in the North caves area and bat species present at pond cave, Craters of the Moon National Monument, Butte County, Idaho. National Park Service, Craters of the Moon National Monument, Arco, Idaho. 78p.

Bonnell, M.L. 1967. Emergence and foraging behavior in small populations of Idaho bats. M.S. Thesis, Univ. Idaho, Moscow. 63pp.

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