383.

Indiana Myotis

Myotis sodalis

French: Murin d'Indiana / German: Indiana-Mausohr / Spanish: Ratonero de Indiana

Other common names: Cluster Bat, Indiana Bat, Social Bat

Taxonomy. Myotis sodalis G. S. Miller & G. M. Allen, 1928,

“Wyandotte Cave [Crawford County], Ind[iana].,” USA.

Subgenus Pyzonix; lucifugus species group. See M. evotis and M. volans . Monotypic.

Distribution. E USA in Iowa, SW Wisconsin, Missouri, Illinois, N & S Michigan, Indiana, Ohio, Pennsylvania, New York, Vermont, New Hampshire, Massachusetts, Connecticut, N New Jersey, W Maryland, W Virginia, West Virginia, W Oklahoma, N Arkansas, Kentucky, Tennessee, W North Carolina, N Mississippi, Alabama, and N Georgia.

Descriptive notes. Head-body 42-48 mm, tail 28-45 mm, hindfoot 7-9 mm, ear 10- 15 mm, forearm 35-40 mm; weight 5-10 g. Fur of the Indian Myotis is soft and dull. Dorsal pelage is dark to light brown or grayish brown (hairs with dark bases, paler middles, and darker tip); venter is buffy brown (hairs with slat bases and grayish white tips). Skin around face is pinkish brown; membranes and ears are dark brown. Ears are medium-sized; tragus is short and narrow, with relatively bluntly pointed tip. Feet are relatively small, with haired toes; calcaris weakly keeled, but more so than some other Nearctic Myotis (such as the Little Brown Myotis, M. lucifugus). Compared with the Little Brown Myotis, skull has slightly more pronounced sagittal crest and generally narrower braincase and interorbital constriction. Chromosomal complement has 2n = 44 and FN = 50.

Habitat. Wooded or semi-wooded upland forests, often associated with streams and ponds, riparian and floodplain forests, and open fields from sea level up to elevations of 1746 m.

Food and Feeding. Indiana Myotis eat variousinsects, primarily Lepidoptera, Diptera, Coleoptera, Hymenoptera, and Trichoptera. Females appearto shift diets during pregnancy and lactation; lactating females in Indiana eat larger amounts of Lepidoptera (more than 70% by volume) than non-lactating females. Diets of pregnant females included ¢.90% small, soft-bodied insects of Diptera (41-5%), Lepidoptera (30-8%), and Trichoptera (17%). During postlactation, females and juveniles feed mostly on Lepidoptera (53-7%) and some Coleoptera (13-3%) and Diptera (12:5%). Stomachs of four individuals in Indiana in summer included Hymenoptera (50% by volume), Coleoptera (24%), and Homoptera (19%). There appears to be a shift to larger and harder bodied insects by the end of summer. Southern colonies appear to feed more on terrestrial insect species; northern colonies seem to feed more on insects in wetlands.

Breeding. Indiana Myotis are polygynous; one male mates with multiple females. Mating occurs mostly during swarming in autumn in October-November, but it has been recorded in winter and even into early spring in rare cases. Ovulation, fertilization, and implantation do not occur until spring, and one young is born per female in late June and July. Between birth and weaning, mortality has been estimated at ¢.8%. Weaning occursafter 25-37 days based on anecdotal reports with volant young being reported in the population in late July. They can live up to 20 yearsin the wild.

Activity patterns. Indiana Myotis leave roosts around dusk to forage through the night, returning in the morning. While roosting during the day, they become torpid to conserve energy. Day roosts in summer are under bark of large trees, in tree hollows, under bridges, and occasionally in buildings and crevices. They roost in a wide variety of trees and prefer trees with exfoliating bark and apparently dead treesto live trees. Maternity colonies occur primarily in upland habitats. They hibernate through winter and swarm to caves far from their summer foraging sites. They prefer medium-sized limestone cavesfor hibernation, with pools and large shallow passageways. They typically hibernate in large clusters in the coldest part of the cave and prefer sites with mean ambient mid-winter temperatures of 4-8°C; they might move to deeper parts of the cave as winter progresses. More active and smaller clusters tend to be found in warmer parts of the cave. Hibernating in coldest parts of the cave ensures that metabolic rates will be low enough so that fat reserveslast through six months of hibernation. They avoid areas = below freezing and occupy caves with humidity of 66-95% (mean 87%). During swarming in autumn before hibernation, females roost in warm parts of the cave. Females were reported immediately entering hibernation upon finding the hibernacula in October; males remained active to seek out mates. They arouse periodically throughout winter to forage (estimated at every 8-10 days). Indiana Myotis leave their hibernacula from April to earlyJune, and females leave earlier than males. Calls are steep FM sweeps, with average start frequency of 74 kHz, end frequency of 41 kHz, peak frequency of 50 kHz, and maximum duration of 3 milliseconds in New York. Echolocation and vision are relied on heavily during flight; indoorflight experiments showed that when individuals were blinded, they were reluctant to fly and crashed into objects, but they only crashed into windows when not blinded. Vision is also thought to be more important in long-term homing because blinded individuals were unable to effectively navigate over long distances, but they could home over small distances.

Movements, Home range and Social organization. Male and female Indian Myotis roost together in cave hibernacula and can numberin the thousands. They form large and irregularly shaped clusters in hibernacula, generally on flat surfaces of ceilings and walls. In spring, females form small maternity colonies of up to 28 individuals or roost alone to give birth to and raise young; males roost alone. They use the same roost sites from year to year, but regularly switch among roosts throughout summer. They might also switch hibernacula in winter, but this might have been because of disturbance. In autumn and spring, they migrate up to thousands of kilometers from summerforaging areas to hibernacula. In autumn, they swarm to hibernacula in large numbers, generally moving from northern latitudes to the southern and central parts of their distribution. Major hibernacula are known in Indiana, Illinois, Kentucky, and Missouri. Males roost in trees near a hibernaculum, waiting to mate with swarming females. During this time, males in Kentucky were found in dead trees on upper slopes and ridge tops within 2-4 km of the hibernaculum, and in West Virginia, they roosted in trees near ridge tops within 5-6 km ofit, switching roosts almost daily. Home ranges average 625 ha in autumn and 255 ha in spring. They do not defend territories but possibly defend space in maternity colonies or hibernacula. Indiana Myotis roost will with Gray Myotis (M. grisescens), Little Brown Myotis, Northern Myotis (M. septentrionalis), South-eastern Myotis (M. austroriparius), Big Brown Bats (Eptesicusfuscus), and Tricolored Bats ( Perimyotis subflavus). Predators include American Minks (Neovison vison), pilot black snakes (Pantherophis obsoletus), and eastern screech-owls (Megascops asio).

Status and Conservation. Classified as Near Threatened on The IUCN Red List. The Indiana Myotis is federally listed as Endangered in the USA by the Endangered Species Act of 1973, and the US Fish and Wildlife Service developed a recovery plan in 1983. It is widespread but has experienced steady declines in recent years. Total known population at major hibernacula was ¢. 883,720 in the 1960s and 1970s, ¢.679,170 around 1980, 473,970 around 1990, and 387,300 in 2003—a decline of ¢.50% since the 1960s to 2003. Declines are most severe in Missouri and Kentucky, where the total decline totaled 430,000 bats. Many major hibernacula in West Virginia, Indiana, Illinois, and Vermont have experienced major declines since the 1950s. In the southern part of the distribution, populations in hibernacula declined 82% from the 1960s to 2003. Nevertheless, populations appear stable to slightly increasing in some places such as Indiana in 2001. Hibernacula in the Midwest and Northeast apparently increased by 35% from the 1960s to 2003. A 2012 report found that total population remained relatively stationary from 1983 to 2005 but with local increases and decreases in various regions. Total population in 2005 was estimated at 457,000 individuals, one-half as many as in the 1960s. About one-half of the population in 2005 hibernated in caves in southern Indiana, with an estimated population of 207,000 individuals. Other large populations occur in Missouri (65,000), Kentucky (62,000), Illinois (43,000), and New York (42,000). The most significant threat is human disturbance, especially at hibernacula, causing accidentally arousal of individuals, depletion of energy reserves, and lower survival rates through winter. Vandalism and commercialization of caves also results in excessive disturbance. Poorly designed gates at cave entrances and changes in cave temperature due to the addition of other entrances can also affect roosting bats. Summer habitat loss from general habitat destruction, poor forest management, agricultural practices, and urbanization is also a major threat. The most recently identified threat, which is also affecting other eastern North American bats, is White-nose Syndrome caused by the fungus Pseudogymnoascus destructans. Effects of White-nose Syndrome on populations of Indiana Myotis have not yet been well studied, but limited studies show that the disease is stalling and in some cases reversing population gains in populations in Indiana.

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