California Myotis
A small bat that forages in arroyos and other arid regions, very similar to the western small-footed myotis.
About This Species
This is a small, pale-colored myotis. The hairs of the dorsum are yellowish brown and lack burnished tips. The braincase rises abruptly above the rostrum. The only other Colorado myotis as small as the California myotis is the western small-footed myotis, which may be darker brownish in color, has dorsal hairs with brassy, burnished tips, a smaller hind foot and a skull with a flat profile, the forehead rising gradually from the rostrum. Care is needed to distinguish the species in the field, and certain identification may require comparative material in the museum.
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 of nine individuals from northwestern Colorado averaged 83.4 mm, length of forearm averaged 33 mm and weight averaged 4.8 g. Wingspan is about 210 mm.
Range
Like a number of other species of myotis, this is a bat of western North America, ranging from central Mexico north to British Columbia and from the Pacific Coast to Colorado, where it occurs at lower elevations in valleys and canyons along the Western Slope.
Habitat
This is a species of semi desert habitats, including pinyon-juniper woodland and desert scrub. The animals roost by day in rock crevices, mines, caves, buildings, beneath bridges or behind loose bark. Night roosts include trees, shrubs and structures such as porches, eaves and outbuildings. Night roosts are dark and sheltered from wind. The winter range of Colorado's population is unknown, but the animals probably hibernate in the state, making local movements to suitable hibernacula in rock crevices, caves and mines.
Diet
The California myotis emerges in early evening to feed, just after the tiny canyon bat, which has a butterfly-like flight. It forages in arroyos, gaps between trees and near boulders and cliffs. It is active until about midnight and then again about dawn. Typical food includes flies, moths and spiders.
Reproduction
Copulation occurs in fall, and sperm are stored over winter by the female. Fertilization and implantation take place in spring. Exactly when implantation occurs is not known, so the gestation period has not been calculated, but probably takes about six weeks. A single young is born to a female in a nursery colony or alone, in May or June or early July. Lactating females have been taken in Colorado as late as August.