Bats are an important part of Michigan’s natural world, often flying unnoticed in the night sky. These creatures are the only mammals capable of sustained flight, playing a key ecological role. Michigan’s diverse landscapes, from dense forests to urban areas, provide varied habitats for these nocturnal animals. They navigate their surroundings and locate prey using echolocation, a biological sonar system.
Meet Michigan’s Bat Species
Michigan is home to nine distinct bat species, all of which are insectivores. Each species has unique characteristics and habitat preferences.
The Little Brown Bat (Myotis lucifugus)
The Little Brown Bat (Myotis lucifugus) is common across the state, identified by its reddish-brown to dark brown fur and 10-inch wingspan. They often roost in large colonies in hot attics, cabins, or under shingles in summer, and hibernate in caves or mines in winter. These bats frequently forage for aquatic insects over water bodies, consuming hundreds of mosquito-sized insects hourly.
The Big Brown Bat (Eptesicus fuscus)
The Big Brown Bat (Eptesicus fuscus) is one of the most frequently encountered species in Michigan homes, known for its adaptability. It has a reddish-brown to dark brown coat, a large nose, and a wingspan ranging from 12.8 to 13.8 inches. These bats primarily feed on beetles, moths, and flies, often roosting in buildings, barns, and hollow trees.
Eastern Red Bats (Lasiurus borealis)
Eastern Red Bats (Lasiurus borealis) are solitary bats with long, silky fur with a distinctive red tinge, with white shoulder markings. Their wingspan can reach up to 13 inches, and they prefer to roost among the leaves in trees, blending well with dead foliage. They consume a variety of insects, including beetles, ants, and flies.
The Hoary Bat (Lasiurus cinereus)
The Hoary Bat (Lasiurus cinereus) is Michigan’s largest bat, with a wingspan up to 15 inches. Its dark fur is tipped with white, giving it a frosted appearance, and short, rounded ears. This solitary species spends summers roosting in forest trees near water and preys on beetles and moths.
Silver-haired Bats (Lasionycteris noctivagans)
Silver-haired Bats (Lasionycteris noctivagans) are characterized by their dark fur with silver-tipped hairs, for a frosted look. With an 11-inch wingspan, they roost behind loose tree bark. Though present in Michigan, they are not commonly found in buildings.
The Tri-colored Bat (Perimyotis subflavus)
The Tri-colored Bat (Perimyotis subflavus), formerly known as the Eastern Pipistrelle, is one of the smallest bat species in the United States, with a 9-inch wingspan. It has tricolored fur, with a yellowish-brown base, a darker middle, and lighter tips. This colonial bat is often found in the Upper Peninsula and rarely roosts in human structures.
Northern Long-eared Bats (Myotis septentrionalis)
Northern Long-eared Bats (Myotis septentrionalis) are distinguished by their long ears and a pale to dark brown coat, and a 10-inch wingspan. They fly and forage for insects in forested areas, often catching prey in flight or from the ground. Their preferred roosting sites include hollow trees or under bark.
The Indiana Bat (Myotis sodalis)
The Indiana Bat (Myotis sodalis) is a medium-sized bat with dull grayish-chestnut fur and a 9 to 11-inch wingspan. These bats form large colonies in summer, primarily under loose tree bark, and hibernate in caves or abandoned mines during winter. They feed on various insects, including moths, beetles, and mosquitoes.
Evening Bats (Nycticeius humeralis)
Evening Bats (Nycticeius humeralis) are colonial bats found primarily in southern Michigan. With a 10-inch wingspan, they are distinguished by a blunt tragus at the base of their ear. These bats often roost in trees but may also use buildings, consuming a range of flying insects.
Conservation Status and Threats
Michigan’s bat populations face significant threats. One of the most devastating threats is White-nose Syndrome (WNS), a fungal disease that arrived in Michigan in 2014. This cold-loving fungus infects bats during hibernation, causing them to awaken more frequently and deplete their fat reserves, leading to starvation.
WNS has caused severe population declines, with some species experiencing mortality rates of 80-100% in affected hibernacula. The Tri-colored Bat and Northern Long-eared Bat have been particularly hard hit, with declines exceeding 90% in some regions. While the Big Brown Bat has shown more resilience due to its tendency to hibernate in above-ground structures like houses, less conducive to fungal growth, other species remain highly vulnerable. Both the Indiana Bat and the Northern Long-eared Bat are federally endangered, and the Tri-colored Bat was listed as endangered in 2022.
Habitat loss also threatens Michigan’s bats. Urbanization and deforestation reduce the availability of suitable roosting sites and foraging areas. Bats rely on specific environments such as old-growth forests, hollow trees, and abandoned mines for raising young and hibernating.
Wind energy development also poses a threat to bat populations. Industrial wind turbines are a significant cause of bat fatalities in the U.S., second only to White-nose Syndrome. Bats can be killed by direct collision with turbine blades or by barotrauma, lung damage caused by rapid pressure changes near the spinning blades. Some migratory tree bats, like the Hoary Bat, appear to be attracted to turbines, increasing their risk.
Coexisting with Michigan’s Bats
Bats provide significant ecological benefits to Michigan’s environment, primarily through their role in insect control. A single bat can consume hundreds to over a thousand mosquito-sized insects in an hour, which helps reduce pest populations and the need for chemical pesticides in agriculture.
Many common misconceptions about bats persist, but these creatures are generally shy and non-aggressive. Bats are not blind; they possess good eyesight and use echolocation for navigation and hunting in the dark. They do not intentionally fly into people’s hair, and despite popular myths, less than one percent of bats carry rabies. A bat found behaving strangely, such as flying during the day or appearing disoriented, should be given space.
If a bat is found inside a home, it is important to avoid direct contact. If there’s any possibility of contact with a person or pet, especially if someone was sleeping or impaired, the bat should be captured safely and tested for rabies by local health authorities. Otherwise, the bat can often be guided out by opening windows and doors, allowing it to escape at dusk.
Individuals can contribute to bat conservation in several ways:
Protecting and preserving natural habitats, such as forested areas and standing dead trees, provides crucial roosting and foraging sites.
Installing bat houses can offer alternative roosting locations, particularly for colonial species like the Little Brown Bat and Big Brown Bat.
Minimizing the use of insecticides helps by ensuring a healthy insect population for bats to feed on.
Avoiding disturbance of known bat hibernation sites, especially during winter, prevents unnecessary energy expenditure that can threaten their survival.