Indiana Bat - Myotis sodalis
![[photo of Indiana Bat]](images/bat1.jpg)
The Indiana bat is known as the "social bat". Indiana bats summer along streams and rivers in north Missouri, raising their young under bark of certain trees. They hibernate through the winter in caves and abandoned mines in the Ozarks. These bats are threatened by habitat loss and human disturbance at their hibernating sites. The Indiana Bat is listed ENDANGERED by the Missouri Department of Conservation and ENDANGERED by the U.S. Fish and Wildlife Service.
Identification
![[drawing of Indiana Bat]](images/bat2.gif)
The Indiana bat is a medium-sized bat that is closely related to the little brown bat, the gray bat, and the keen's bat. Its average body length is about 2 inches, and its wingspan measures 8 inches. Individual bats may weigh about 1/4 ounce (as much as a quarter). Indiana bats have brownish-gray fur with cinnamon overtones. The ears and wing membranes are blackish-brown.
Indiana bats are difficult to distinguish from little brown bats and keen's bats. The main identifying feature of the Indiana bat is a distinct keel on its calcar (the cartilaginous supporting structure on the rear edge of its tail membrane). The little brown bat is a common bat found on farms and in cities. Little brown bats' hind feet are larger and have longer, thicker hairs. They also lack keels on their calcars. Keen's bats have longer ears. The gray bat, also a federally endangered species, is larger. The gray bat's wing attachment is to the ankle and not to the back of the toes, as in the Indiana bat. The keel may be small or non-existent on its calcar.
For a technical description of this animal, refer to:
![[map of Missouri]](images/bat3.gif)
Schwartz, C.W. and E.R. Schwartz. 1986. The Wild Mammals of Missouri. University of Missouri Press. Columbia, Missouri. 356 pp.
Habitat and Distribution
Indiana bats need cool caves with stable temperatures of around 40 degrees Fahrenheit and relative humidities ranging from 66% to 95%. Of Missouri's 5,000 or so known caves, only 27 have ever had sizeable Indiana bat populations. Female Indiana bats enter hibernation in early autumn, shortly before the males. Bats hibernate in clusters of several hundred to several thousand and can be clustered so tightly that there may be 400 bats per square foot.
Indiana bats emerge from hibernation in early spring and begin migrating to their summer roosting and foraging areas. Indiana bats often forage in the treetops along riparian (stream and river) forests and floodplains, as well as in upland forests and in low fields and pastures. They are entirely insectivorous, eating primarily moths, but also mosquitoes and aquatic insects.
In the summer, females gather beneath the loose bark of living and dead trees in maternity colonies of 50 to 100 individuals. Some males also migrate to floodplains and upland forest during the summer, while many remain near their hibernation caves. Indiana bats exhibit great loyalty to their roosting and hibernating sites and will return to the same locations year after year. The Indiana bat does not hibernate or roost in houses or man-made structures.
Over 85% of the total population of Indiana bats hibernate in only eight specific locations, three of which are located in Shannon, Washington, and Iron counties of Missouri. Summer roosting Indiana bats have been recorded in northern Missouri.
Cause of Historic Decline
Historical causes of population decline in the Indiana bat are mainly the result of man's activities. Because the Indiana bat migrates between a summer and winter range, it is faced with threats specific to each area. During the winter, human disturbance to hibernating bats has been a primary cause of decline. The installation of gates at some cave entrances also caused population declines by altering temperatures and humidity within the cave, or making the cave inaccessible to the bats. In addition, as reservoirs were created, some caves were lost to flooding. Historically, stream channelization, deforestation, and agricultural development have threatened Indiana bats in their summer range. Populations of Indiana bats have been declining since the 1970's. Landowners' actions and activities can help recover this species.
Current Threats To Indiana Bats
WINTER RANGE
- Disturbance of hibernating bats - During the winter, Indiana bats enter a state of hibernation and do not feed. Fat reserves stored prior to hibernation are limited and are only enough to sustain the bats until spring. When Indiana bats are disturbed while hibernating, they become aroused and can use up 10-30 days of stored fat.
- Cave degradation - Slight or moderate changes in a cave's environment can cause the cave to become uninhabitable or inaccessible. Improper installation of cave gates can cause temperatures to change, disrupt air flow, alter lighting, or block the cave's entrance. Caves used for commercial purposes disrupt natural processes and may cause bats to abandon the cave and seek shelter in less suitable locations.
SUMMER RANGE
- Habitat modification - Changes in habitat resulting from stream channelization, bank modification, agricultural development, and conversion of forested land have affected the amount and quality of bat habitat. Wooded riparian areas are needed by bats for foraging, roosting, and breeding.
- Loss of suitable roosting trees - Indiana bats raise young and roost under the bark of trees in riparian and upland forests. Harvesting trees and removing dead trees reduces the amount of available habitat and forces the bats to utilize areas where the potential for disturbance or predation may be higher.
- Pesticides and pollution - Indiana bats spend the summer in agricultural areas and are potentially at risk to pesticide contamination. Indiana bats, like many other North American bats, are insectivorous. Contamination of waterways that eliminates aquatic insects may hurt local populations of Indiana bats.
Protection and Management: Steps Toward Recovery
- Avoid disturbing hibernating bats. - Indiana bats tend to hibernate inside a cave near the entrance and are easily disturbed. Avoid caves known to have hibernating bats, and respect signs and gates constructed to notify people of resident bats. Bats need a cool, pollution-free environment throughout the winter, so avoid building fires in or near a cave's entrance.
- Maintain or improve cave habitats - in areas where bats hibernate. Maintain a minimum of 20 acres of forested land around the cave entrance. Do not remove vegetation from the cave entrance. Proper gate construction is essential in order to allow unobstructed air flow and to maintain the accessibility of the cave. If a bat cave is located on your property and you wish to construct a gate, please contact the Missouri Department of Conservation for technical assistance.
- Avoid altering riparian habitats and modifying streams. When modifications are unavoidable, leave at least 100 feet of natural vegetation on each side of the stream bank.
- Minimize the removal of timber from riparian zones. When possible, leave dead trees standing and only remove trees when Indiana bats are not likely to be present (typically from September 1st to April 1st). Indiana bats tend to favor species of oak and hickory for roosting but may also use cottonwood and elm trees. If timber harvesting does occur, efforts should be made to leave mature individual trees with diameter greater than 14 inches, especially species with loose, shaggy bark (oaks and hickories). Maintain continuous forest vegetation in riparian zones.
- Reduce the use of pesticides near summer foraging areas. Indiana bats consume large quantities of insects during the summer and are at risk to exposure to pesticides. Spraying should be avoided around riparian areas and forested roosting areas.
Missouri and federal law prohibits the importation, transportation, sale, purchase, taking, or possession of animals on the State or Federal lists. Damage of hibernation caves while bats are present is also prohibited.
For more information on Indiana bats, or to report sightings of this species, contact:
Endangered Species Coordinator or Wildlife Ecologist Missouri Department of Conservation P.O. Box 180 Jefferson City, MO 65102 573/751-4115
