Bats of Colorado > Fringed myotis (Myotis thysanodes)
The fringed myotis is distinguished by its relatively long ears and a conspicuous fringe of stiff hairs on the trailing edge of the uropatagium. The pelage varies in color from pale to rich brownish, individual hairs being lead-gray at their bases. The membranes are dark. Total length of five individuals from northwestern Colorado averaged 86.8 mm; length of forearm averaged 40.1 mm: and weight averaged 7.5 g. The wingspan is 265-300 mm. The only other medium-sized myotis with long ears is the long-eared myotis, a species in which the ears are 21-24 mm long (by contrast with ears 17-20 mm long on the fringed myotis).
This is a western species, ranging from the Isthmus of Tehuantepec in Mexico north to British Columbia, Montana and Wyoming. The animals apparently occur as scattered populations at moderate elevations on the Western Slope, along the foothills of the Front Range and the mesas of southeastern Colorado. Maximum elevation is 7,500 feet.
The fringed myotis is a species of coniferous forest and woodland at moderate elevations in Colorado. Records of occurrence are few, and the species isn't common in the state, but perhaps it is simply widely distributed. Typical vegetation of the habitat includes ponderosa pine, pi-on, juniper, greasewood, saltbush and scrub oak. The animals roost in rock crevices, caves, mines, buildings and trees. They are known to hibernate in caves and buildings. Where this species has been studied well, migration seems not to be extensive.
Breeding takes place in fall; ovulation, fertilization, implantation and gestation occur in spring, as sperm are stored over the winter in the female's uterus. Up to several hundred females congregate in nursery colonies. Males are solitary while the young are reared. In a typical season, all mature females breed. The single young is produced after a gestation of 50 to 60 days. Newborn young are hairless and pinkish, and their eyes are closed. Growth is rapid, however, and they can fly by 20 days old. Maximum known longevity is 11 years. Although some individuals may live even longer, the average lifespan is much shorter than that.
The fringed myotis feeds on such arthropods as moths, daddy longlegs and beetles. They forage along water, above shrubs and woodlands or low over meadows (apparently in more open areas than the long-eared myotis), emerging to feed about two hours after sunset. Flight speeds average about 9 miles per hour.
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