Fringed Myotis
Order Chiroptera : Family Vespertilionidae : Myotis thysanodes Miller

Description. A relatively large Myotis with large ears and a distinct fringe of short, stiff hairs on free edge of the membrane between hind legs; tail from 75 to 81% of length of head and body; foot from 50 to 75% of length of tibia; ears projecting about 5 mm beyond snout when laid forward; pelage full and about 9 mm long on the back; upperparts uniform warm buff, tips of hairs shiny, bases fuscus black; underparts dull whitish. Dental formula as in M. californicus. External measurements average: total length, 86 mm; tail, 35 mm; foot, 9 mm; ear, 16.5 mm; forearm, 43 mm.

Distribution in Texas. A western bat known from Texas in the Trans-Pecos region in summer. Two specimens have been captured from northwest Texas (Crosby County), but these were probably seasonal migrants. The fringed myotis has been captured in habitats ranging from mountainous pine, oak, and pinyon-juniper to desert scrub but seems to prefer grassland areas at intermediate elevations.

Habits. These bats roost in caves, mine tunnels, rock crevices, and old buildings in colonies that may number several hundred. This is a highly migratory bat that arrives in Trans-Pecos Texas by May, at which time it forms nursery colonies. These colonies begin to disperse in October, and the winter locales and habits of this bat remain a mystery.

This species appears late in the evening to forage. They fly slowly and are highly maneuverable, allowing the bats to forage close to the vegetative canopy or about the face of small cliffs. No data are available on their specific food habits in Texas, but specimens from New Mexico contained mostly small beetles.

The single young is born in late June or early July after a gestation period of 50-60 days. Gravid females captured on June 28 each contained a single fetus nearly ready for birth. Immature individuals have been found in July and August in colonies of adult females. The young are able to fly at 16-17 days of age. As with other species of Myotis, adult males and females do not associate with each other in summer.

Photo credit: Merlin D. Tuttle, Bat Conservation International.

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