Yuma Myotis
The Yuma myotis forages along waterways for a variety of insects.
About This Species
This is a medium-sized, small-eared, pale grayish to yellowish bat, its dark membranes contrasting fairly strongly with the fur. Among Colorado's species of Myotis, only the California myotis and the small-footed myotis are as pale in color. The small-footed myotis is more yellowish, less grayish and both it and the California myotis are smaller than the Yuma myotis.
Living with Bats
There are 18 species of bat that call Colorado home. These amazing mammals are not only fantastic insect control, but are also valuable pollinators. Learn more about how humans and bats can live in harmony in our guide.
Bat Conservation
Bats remain one of the most mysterious land mammals, especially in Colorado, where 18 species spend at least part of the year. For example, the little brown bats in our state seem to hibernate differently than those on the east coast, and we are constantly learning about their whereabouts, habitats and behaviors. Our current research suggests that bat populations in Colorado are doing quite well.
One little brown bat can eat up to 18,000 small insects (like mosquitoes) each night. Their economic impact is estimated to be billions of dollars, and much of the agricultural industry relies on their insect control.
Beyond their economic impact, bats flaunt some impressive adaptations. They are the only mammal that truly flies, which requires a very unique anatomy. Their upside-down lifestyle requires adaptations in their “feet” to consistently grip. If people hanged upside down for even an hour, we’d lose consciousness; bats have developed amazing blood pressure accommodations to fit the lifestyle.
We are currently involved in a monitoring partnership called the North American Bat Monitoring Program (NA Bat). The program utilizes acoustic surveys to collect information on bat populations without interfering with their behaviors. We also are using PIT tags, like the chips put in household pets, to monitor a number of maternity sites. While data collection will take years, we’ve already learned new information about Colorado’s bat population, the most heartening of which is that the population appears larger and more widespread than we’d thought. This is an excellent start to learning more about the species, but we’ve got lots of problem-solving and technological innovation left to do.
Our priorities also include learning more about bats so that we are prepared for the potential spread of White-nose Syndrome. Finding and monitoring bats is crucial to this effort, but also comes with its own challenges. Because bats are small, flying mammals, much of the equipment used to track other species is too heavy for them. And during the winter, Colorado bats are very elusive, choosing to hibernate in small groups often in locations that are inaccessible to people.
More Information:
Physical Characteristics
Total length is 86-88 mm; length of forearm, 34-38 mm; and wingspan, about 235 mm. Weight ranges from 3 to 5 g.
Range
The Yuma myotis occurs widely in western North America, from central Mexico north to British Columbia, Montana and southeastern Colorado. In Colorado these bats occur at moderate elevations in valleys on the Western Slope, in the San Luis Valley and on the eastern slope north to the vicinity of Colorado Springs. Maximum reported elevation of occurrence in Colorado is about 7,900 feet at Conejos in the San Luis Valley.
Habitat
This is a species of dry shrubby country, but it appears to be tied more closely to water and river canyons than any of Colorado's other bats. Typical habitat is in pinyon-juniper woodland and riparian woodland in semi desert valleys. The animals roost in caves, crevices in cliff faces or abandoned buildings and other structures. They forage over water, along streams and rivers, over springs, and among riparian or shoreline vegetation. Early arrival and late departure dates suggest that Yuma myotis hibernate in Colorado, possibly in rock crevices, although locations have never been confirmed.
Diet
Food consists mostly of moths, flies and beetles, but also includes leafhoppers, caddis flies, lacewings and crane flies. The animals forage near water and take many aquatic insects. They are efficient feeders and can fill their stomachs in 15 to 20 minutes. They forage in early evening, usually along the main channel of a stream.
Reproduction
Breeding has not been studied much in Colorado, although lactating females have been captured and a nursery colony was discovered in 1990 in the Colorado National Monument. Elsewhere, the animals are known to form nursery colonies of upwards of several thousand individuals in caves or attics. Apparently all adult females in a population breed. A single young is born late in the spring or early in the summer. Breeding colonies have been discovered along the Western Slope and in the southeastern part of the state. Males are solitary as the young are reared.