Hoary Bat
This bat is distinctive, with fur that appears tipped in hoar frost.
About This Species
The hoary bat cannot be mistaken for any other species. The tips of the hairs are white or grayish with brown shafts that appear similar to hoar frost, giving the bat its name. The ears are short and round with a striking black border. Little is known about the natural history of this species in Colorado; it deserves more study.
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
This is one of Colorado's largest bats with a wingspan of about 400 mm, a body and tail about 140 mm long, and a forearm 50-58 mm long. Hoary bats weigh approximately 25 g.
Range
The hoary bat is widespread, ranging from northern Canada to Guatemala, and probably occurring in all states except Alaska - even in Hawaii, where it is the only native land mammal. In Colorado, the hoary bat probably occurs statewide from the plains to timberline.
Habitat
The hoary bat is a solitary, tree-roosting species and can be expected to live in any habitat with trees. It is migratory with the sexes migrating north together in spring. During summer, the sexes separate, however, perhaps to reduce competition for food while females give birth and rear the young. Hoary bats arrive in Colorado in April and are gone by November. There is no record of hibernation here.
Diet
The hoary bat prefers moths but also feeds on beetles, wasps, grasshoppers and even small bats. An open-air forager, the animals seem to approach moths from the rear, severing the abdomen and thorax from the rest of the body. Flight is swift and direct, and a keen observer can readily identify the hoary bat by its flight pattern, body size and relatively long, narrow wings. It tends to emerge later in the evening to forage than most other local bats.
In Colorado its foraging period seems to be varied, however, due to the vagaries of local weather. The hoary bat has been seen foraging near street lamps or other outdoor lights.
Reproduction
Most females give birth and raise their young in northern and eastern North America, although a few females rear young in Colorado. Litter size is generally two with a range of one to four. Birth occurs between May and July. The mother can forage with the young clinging to her nipple, but generally the young are left at the roost site. Young begin to fly at about 30 days of age. Copulation usually occurs during the fall migration but may take place on wintering grounds. Implantation of the new embryos is postponed until spring when growth and development are completed.