Little Brown Myotis and Northern Myotis, Myotis lucifugus and Myotis septentrionalis Facts
Common Names: Little brown bat, Northern bat, or vesper bats
Species: Myotis lucifugus (shown) & septentrionalis
General Description The little brown bat is a small member of the vespertilionidae family. The hair on its back is long, with glossy tips. The pelage is long and full, with upperparts ranging from bronzy brown to olive brown, and underparts grayish. Males and females are approximately the same size. Average external measurements of length are 85mm, tail 35mm, foot 9mm, ear 13mm and forearm 39.5mm. Weight ranges between 7 and 9g. The northern bat is also small, but it has a uniform dull, gray-brown pelage. This bat has relatively long ears and an unkeeled calcar. The average external measurements for both males & females are: length 78mm, tail 26mm, foot 9mm, ear 13mm and forearm 35mm.
Geographical Distribution and Habitat Requirements One fourth of all mammalian species are bats. They inhabit all the continents except for Antarctica. These bats are widely distributed over eastern and northern North America. They spend the daytime in crevices in walls, caves, attics or other places of concealment and emerge shortly before dark.
General Biology Chiropterans are unique because they are the only true flying mammals. These species have the ability to fly and use echolocation. They use echolocation by emitting pulses of very loud, high frequency sound. When the sound bounces off an object and returns to the bat, it is processed into an image by the brain. Flying and echolocation allow these bats to exploit airborne food sources and dark habitats. These bats commonly forage along forest edges, over forest clearings, and occasionally over or near water. Food consists of insects, especially moths, captured in flight. (They can catch about 500 per hour). These bats are described as slow, straight flyers, and tend to cruise at 20kmph. These species are diurnal, coming out to forage at dusk and dawn for 2-3 hours. When not foraging, these bats rest and digest food. These species are true hibernators, which means that their body temperature drops below 5oC. Bats mate just before hibernating, usually in November, but fertilization is usually delayed until hibernation ceases. Delayed fertilization is useful, as hibernating bats do not have the energy to waste on producing young. Bats will mate for their entire life span. Gestation period is 50-60 days, and there is usually only one bat per litter. Newborns are naked and blind, and are carried with the mother for a few days, after which they are left hanging in the roost. After 3-4 weeks, the baby can fly and is weaned from the mother. The young reach full growth at 8 weeks, but females are not sexually mature until 1 year and males 2 years.
Conservation Both of these vesper bats are quite common and diverse. There is no fear that they will become extinct anytime soon. Many people are afraid of bats and wish they would go away, but they have a few good qualities. Thses bats eat insects, therefore they help to keep the population down, and they are indicators of environmental hazards (pesticides). Their main predators are humans and birds, yet the average lifespan is only 4-6 years.