Southeastern Myotis (Myotis austroriparius)

Protection Status Notes
Populations of up to 250,000 individuals have been documented as lost in caves in northern Florida, and the species is either rare or extirpated from many areas in the lower Ohio River Valley. M. austroriparius is considered a species of special concern by the U.S. Fish and Wildlife Service. Decline has been documented in many areas, with hundreds of thousands lost in single incidents.
Description
Myotis austroriparius is a small insectivorous bat with short, thick, woolly fur, which is bi-colored, russet, dark gray, or black at the base, and whitish at the tips. This species molts in late summer, shedding a lighter, rusty coat to acquire one of dark gray. It has unusually long toe-hairs which extend past the ends of its claws. Its calcar is not keeled. Its tragus is relatively short and blunt compared to other myotis. The southeastern myotis has a high domed skull with a sagittal crest (a bony ridge which runs along the top of the skull from front to back). Its forearm is 35-42 mm long, and it weighs 5-9 g. It differs from the gray myotis, which has uni-colored fur and lacks contrasting whitish tips on its venter. The little brown myotis also lacks contrasting whitish tips on its venter.
Life History
The Southeastern Myotis is a colonial species which spends its winters in the vicinity of its summer territories. It hibernates in winter in northern areas, though southern populations emerge to forage during warm spells. Northern populations breed between late October and early December before entering hibernation, however, Florida populations remain active for most of the winter and breed in the early spring. Beginning in mid-March, females congregate in nursery colonies in relatively warm caves with high domed ceilings or tree hollows not far from water. Nursery roosts must be warm, or capable of trapping the bats' body heat, and out of reach of climbing predators. They give birth in late April or early May, usually to twins. Pups are born pink and hairless with their eyes and ears closed. Flightless young cluster together when mothers leave the roost to feed. Pups are able to fly in 5 to 6 weeks.

The Southeastern Myotis roosts in a variety of shelters including caves, mines, bridges, buildings, culverts, and tree hollows. During winter, they typically hibernate in tightly packed clusters in caves and mines in northern regions, but often in more exposed areas such as bridges and hollow trees in the South. During the summer, males roost separately, either singly or in small bachelor groups. This species often shares roosts with gray myotis, Mexican free-tailed bats, eastern pipistrelles, and Rafinesque's big-eared bats. In northern areas and in Florida, most nursery colonies are found. Florida nursery colonies generally include 2,000-20,000 individuals, though some hold up to 100,000 bats.

The Southeastern Myotis emerges after dark and flies directly to a nearby pond or stream. This bat is a rapid, steady flyer, and it hunts close to the water, where it catches insects such as midges, mosquitoes, small moths, small beetles, and craneflies. It is not known how long this species lives in the wild.
Habitat
The Southeastern Myotis roosts in a variety of shelters including caves, mines, bridges, buildings, culverts, and tree hollows. It prefers oak-hickory to mixed conifer-hardwood habitats and is often associated with human habitations near streams or lakes.
Distribution
The southeastern myotis, as its name implies, lives in the southeastern United States, from coastal North Carolina south into peninsular Florida, west through Louisiana and into eastern Texas and southeastern Arkansas. It also lives along the lower Ohio River Valley in Kentucky, Indiana, and Illinois.

In Texas this species occurs westward to the Pineywoods region of East Texas.
Threats and Reasons for Decline
Vandalism in caves is a primary cause of decline. Impacts of forestry practices are unknown. Management practices that change water quality and aquatic insect abundance are likely to affect this species. Loss of upland roosts also leaves the species extremely vulnerable to drowning during floods.

Predators include corn snakes, rat snakes, owls, and opossums.
Ongoing Recovery
Locating and protecting key cave roosts is important, though full status evaluation and an understanding of critical habitat requirements necessitate further study of forest-dwelling populations and their roosting needs.

No records of longevity are available.
Other
Little is known about this species' roosting requirements outside of caves, especially in caveless forested areas. Loss of upland roosts has led to drowning of large colonies during floods, and the impact of such threats warrants further investigation.
For more information
  • Additional details can be found in the online version of The Mammals of Texas for the Southeastern Myotis

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