by Lewis Young
At first glance, this bat is similar to several other small bats in Montana, but the name is a giveaway for a prominent feature that helps distinguish it. The ears are very large and long compared to the body size and extend 5 millimeters (0.2 inches) or more beyond the nose when gently laid forward. The ears themselves are more than 21 mm long (0.8 inches). The fur is usually dull brown to straw-colored and individual hairs are black at the base. Both the ears and wing membranes are black. Wingspan is 10-12 inches (25-30 centimeters), and weight is 5-8 grams (0.2-0.3 ounces). Life span can be 22 years.
Long-eared Myotis (Myotis evotis) range across most of the western U.S., southwestern Canada, and into Mexico. They are found all across Montana in suitable habitat.
These bats may be found in a diverse array of habitats including lowland, montane, and subalpine woodlands, forests, shrublands, meadows, wooded stream courses, and areas over water bodies. The author’s experience in Montana is that Long-eared Myotis are most commonly found in or near forested areas with large, mature to old-growth trees. They are insectivorous eating primarily moths and beetles but also flies, lacewings, true bugs, and spiders. Prodigious quantities of insects are consumed each night. Pregnant or lactating females often eat their own weight. Typically emerging 10-40 minutes after dark, they feed for a period, then go to a night roost to digest and rest before going out again to feed before daylight, although the time of emergence and temporal pattern of foraging seems to vary among different locations or circumstances. Their wing structure makes them highly maneuverable. Besides hawking insects out of the air, they also glean prey from leaves and bark or off the ground. Their mobility also allows them to drink on the wing.
As with all other bats in Montana, echolocation is used to navigate in darkness and find food. Ultra-high frequency sounds are emitted from the mouth and the large ears detect the sound waves reflected off prey and inanimate objects. Long-eared Myotis echolocation calls are in the 30-80 kilohertz range, well above human hearing capability. They also have social calls at much lower frequencies that are audible to humans.
Sexes are segregated in summer with females in small maternity colonies of up to 30. Females have one young per year, usually born in late June or July, and return to previously used maternity roost areas. Mothers can fly with pups attached. Gestation is 50-90 days; the young can fly in 3-4 weeks and are weaned in 5-6 weeks. Breeding occurs in the fall before hibernation but implantation and gestation is delayed until the following spring. Nonreproductive females and males generally roost singly or in small groups.
In summer during daylight hours, they roost in a variety of places such as tree cavities, under loose bark, rock fissures, stumps, and buildings. Roost sites may be switched frequently.
In winter they hibernate at sites that include caves, abandoned mines, and fissures in rocks and soil. Hibernation takes place from October to April and involves an extreme reduction in metabolic rate, heart rate, and respiratory rate that allows them to survive long periods of time without food. The heart rate drops from 200-300 beats per minute to 10 beats per minute, and they may go minutes without taking a breath. The body temperature can also drop to near freezing, depending on the temperature of the bat’s surroundings. Other bodily functions also slow down, which reduces energy costs by about 98%. In this state of “torpor,” bats are experts in high energy efficiency! During hibernation, bats cycle through periods of torpor interrupted by brief periods of arousal when their body temperatures return to normal for a few hours.
Long-eared Myotis are considered yearlong residents in Montana although very few hibernation sites are known. It is possible that some short distance migration occurs between summer and winter.
Their conservation status is considered secure due to the wide distribution and regular occurrence in suitable habitats. However, White-nose Syndrome, the cold-loving fungus that has killed millions of bats in the eastern U.S., may impact Long-eared Myotis when it reaches Montana sometime in the future.
Long-eared Myotis are not easily observed because of their nocturnal activities, but they are a valuable component of our wildlife diversity and play an important role in insect control at night.