Myotis sodalis

Geographic Range

Myotis sodalis , also known as the Indiana bat, is found only in North America. Their range spans from Iowa, Missouri, and northern Arkansas east to western Virginia and North Carolina, and north into New York, Vermont, New Hampshire, and Massachusetts. These areas include both their winter hibernation sites and summer ranges. Indiana bats hibernate in the northern reaches of their range in caves during the winter. In the summer and autumn months Myotis sodalis migrate to summer roosting sites.

• Biogeographic Regions
• nearctic nearctic
  • native native

Habitat

Indiana bats hibernate predominantly in limestone caves, though some hibernate under the bark of dead trees. Cave temperatures range from 3.0 to 7.2 degrees Celsius; warmer temperatures are at the start of the hibernating season in October to November and cooler temperatures during March to April. They roost at elevations from 0 to 1,746 m above sea level (average 1047 m). During the summer, Indiana bats roost under the bark of large trees, under bridges, and sometimes in buildings. Trees in which Indiana bats are known to roost include bitternut hickory ( Carya cordiformis ), oaks ( Quercus ), elms ( Ulmus ), pines ( Pinus ), American sycamore ( Platanus occidentalis ), and eastern cottonwood ( Populus deltoides ).

• Habitat Regions
• temperate temperate
• terrestrial terrestrial

• Terrestrial Biomes
• forest forest
• mountains mountains

• Other Habitat Features
• caves

Physical Description

Indiana bats are small, weighing approximately 7 g with a forearm range of 35 to 41 mm. They are dark grey or brown in color and their fur is considered soft. They are distinguished from other, similar, co-occuring members of g. Myotis by their distinctly keeled calcar, a small cartilage projection from the foot, giving added stability to the wing. Indiana bat fur is soft in comparison to that of the very similar and closely-related little brown bat, Myotis lucifugus , which has fur that tends to be more shiny. Male and female Indiana bats are very similar with the female tending to be a little larger than the male.

• Other Physical Features
• endothermic endothermic
• heterothermic heterothermic
• bilateral symmetry bilateral symmetry

• Sexual Dimorphism
• female larger

Reproduction

Indiana bats are polygynous, with one male mating with multiple females. Males wait at the entrance to winter hibernacula for the opportunity to copulate with un-mated females. This occurs during the "fall swarming" period in October or November. There have been some accounts of Indiana bats copulating in late winter or early spring but this is rare.

• Mating System
• polygynous polygynous

Myotis sodalis copulate in the fall, generally in late October. This is the time right before they enter into hibernation. Pregnancy does not begin at this time, as the females can store sperm over winter. This delayed fertilization allows the young to be born in summer (up to 68 days post fertilization). Females give birth to only one pup (on rare occasions twins) per year. Most pups are born between late June and early July with weaning at about 31 days (range 25 to 37 days). The first born of the season may be volant as early as mid-July.

• Key Reproductive Features
• iteroparous iteroparous
• seasonal breeding seasonal breeding
• gonochoric/gonochoristic/dioecious (sexes separate)
• sexual sexual
• induced ovulation induced ovulation
• fertilization fertilization
• viviparous viviparous
• delayed fertilization delayed fertilization

Females provide care for pups after birth at summer roosting sites. Often maternity colonies are formed and male presence is rare. Females are responsible for providing nourishment for their pups through lactation. Time to weaning is about 31 days and pups are fully independent from their mothers in 2 to 3 months.

• Parental Investment
• altricial altricial
• female parental care female parental care
• pre-fertilization
  • provisioning
  • protecting
    • female
• pre-hatching/birth
  • provisioning
    • female
  • protecting
    • female
• pre-weaning/fledging
  • provisioning
    • female
  • protecting
    • female

Lifespan/Longevity

Indiana bats have lived as long as 20 years in the wild. Their expected lifespan in the wild is 15 years.

Behavior

Indiana bats are social, which may account for their alternate common name, "social myotis." There have been no documented cases of social hierarchies within the species. Males and females hibernate together, but adults separate in the summer months. Maternity colonies contain juvenile males and only rarely adult males. Indiana bats migrate seasonally; to travel from winter hibernacula to summer roosts Indiana bats travel distances up to thousands of kilometers. For example, a banded female caught by mist netting over a river in southern Iowa that had come from a hibernaculum in Missouri.

They have a wide nocturnal foraging area during the summer months. Perhaps this is why the area of suitable summer habitat does not correspond to population densities for this bat. For example, in a forest of up to 5 million hectares, population estimates were small as 10,000 bats. Another area of forest covering 1.7 million hectares was estimated to have 112,500 Indiana bats.

• Key Behaviors
• troglophilic
• flies
• nocturnal nocturnal
• crepuscular crepuscular
• motile motile
• migratory migratory
• hibernation hibernation
• social social
• colonial colonial

Home Range

Home range size of Indiana bats varies by individual as well as time of year. They are an average of 625 ha during the fall, and 255 +/- 89 ha in the spring. These home ranges are not defended. Perhaps the only territory defended is a space within a maternity colony or a hibernaculum, where bats might interact with individuals within 5 square meters of themselves.

Communication and Perception

Indiana bats, like other insectivorous bat species, use echolocation to maneuver through their various habitat types. They have well-developed eyesight which they use to aid with their travels from their winter hibernacula to their summer roosting sites. We can assume that Myotis sodalis individuals do communicate with each other using sound, but there have been no studies to further investigate this. Like other mammals, it is likely that these bats use chemical cues to communicate reproductive state.

• Communication Channels
• visual visual
• acoustic acoustic
• chemical chemical

• Perception Channels
• visual visual
• tactile tactile
• echolocation echolocation
• chemical chemical

Food Habits

Indiana bats consume a diet of insects. A study found that Indiana bats eat insects from five main taxa: Coleoptera (beetles), Diptera (flies), Hymenoptera (bees, wasps), Lepidoptera (butterflies and moths), and Trichoptera (caddisflies). There are also differences in what females eat based on whether they are pregnant or lactating or neither. Lactating females eat greater amounts of coleopterans and trichoperans compared to non-lactating female bats. There are slight differences in diet based on location; southern colonies feed more on terrestrial insect species, whereas more northern bats fed on insects around wetlands.

• Primary Diet
• carnivore carnivore
  • insectivore insectivore

• Animal Foods
• insects

Predation

Predators of Indiana bats include carnivorous animals such as snakes, owls, raccoons ( Procyon lotor ), and other medium-sized mammals. The main adaptations Indiana bats have against predation is that they roost in caves and inaccessible tree crevices, putting them out of reach of many predators. They are also active at night and agile in flight. Myotis sodalis individuals hibernate in large clusters which help ensure survival (and warmth) between October and April. Their cryptic coloration also helps to protect them from predation.

Humans have been known to kill these bats, although they are not eaten. For example, at Carter Caves State park in Kentucky, two men clubbed 105 Indiana bats to death. Humans also unintentionally kill bats by destroying or cutting down summer roost trees or disturbing hibernation sites.

• Anti-predator Adaptations
• cryptic cryptic

Ecosystem Roles

Indiana bats help control insect populations and are prey for bat predators. They are hosts for species of mites ( Steatonyssus occidentalis and Macronyssus crosbyi ) but there have been no documented intestinal parasites. Indiana bats have a direct impact on their cave environment by adding nutrients to the cave with their guano and decomposing bodies.

Economic Importance for Humans: Positive

Indiana bats may impact humans by helping to control pest insect populations.

• Positive Impacts
• controls pest population

Economic Importance for Humans: Negative

Indiana bats can become a nuisance in some places where their summer roots have been destroyed due to increasing human populations. Bats will then find their way into homes and attics to roost. Like most mammals in the United States, Indiana bats also may be carriers of rabies. However, documented incidence of rabies infection in Indiana bats is low. It is also very unlikely that humans will come into close contact with Indiana bats for the disease to be transmitted.

• Negative Impacts
• injures humans
  • carries human disease

Conservation Status

Indiana bats are a federally endangered species and are endangered on the IUCN Red List. They are mostly threatened by habitat loss, and their numbers are monitored. For example, any organization intending to change a habitat where they live must first check for roosting locations, and accommodate the bats if they find them. Humans also disturb Indiana bats through recreational caving, so many of their hibernation areas are now closed off to humans.

Temperate North American bats, including Indiana bats, are now threatened by a fungal disease called “white-nose syndrome.” This disease has devastated eastern North American bat populations at hibernation sites since 2007. The fungus, Geomyces destructans , grows best in cold, humid conditions that are typical of many bat hibernacula. The fungus grows on, and in some cases invades, the bodies of hibernating bats and seems to result in disturbance from hibernation, causing a debilitating loss of important metabolic resources and mass deaths. Mortality rates at some hibernation sites have been as high as 90%. Currently, there is no known cure for white nose syndrome.

Additional Links

Encyclopedia of Life

BioKIDS Critter Catalog

Contributors

Anna Burgess (author), Radford University, Gail McCormick (editor), Animal Diversity Web Staff, Karen Powers (editor), Radford University, Tanya Dewey (editor), University of Michigan-Ann Arbor, Catherine Kent (editor), Special Projects.

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