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Myotis austroriparius (Rhoads, 1897)

Southeastern Bat

Federal Protection: No US federal protection

State Protection: No Georgia state protection

Global Rank: G4

State Rank: S3

SWAP High Priority Species (SGCN): Yes

Element Occurrences (EOs) in Georgia: 36

Habitat Summary for element in Georgia: Caves and buildings near water; large hollow trees in bottomland hardwood swamps


Description

Small bat with slightly wooly fur, and back is yellow-gray to gray-brown with whitish belly, possibly turning orangish in mid-late summer. Large colonies often result in orange fur, possiblly due to ammonia. Females tend to be more orange during the maternity season when in large maternity colonies. Females also tend to be larger than males. Calcar not keeled and plagiopatagium attaches to base of the toe. body length (excluding tail) of 45 – 55 mm (1.7 – 2.1 in), tail (base to tip of tail) of 33 – 44 mm (1.3 – 1.7 in), hind foot (ankle to tip of claw) 10 – 12 mm (0.4 – 0.47 in), ear of 14 – 16 mm (0.5 – 0.63), mass of 6 – 12 g (0.2 – 0.4 oz), and forearm length (outer edge of elbow to wrist) of 35 - 41 mm (1.4 – 1.6 in).

Similar Species

The little brown bat (Myotis lucifugus) is very similar but with no orange color phase and has glossy, not wooly, fur. The southeastern myotis differs from many other Myotis spp by long toe hairs than extends past the claw. Its calcar is not keeled and its tragus is slender and pointed.

Habitat

This species is often associated with habitat of the Rafinesque big-eared bat (Corynorhinus rafinesquii), which includes bottomland hardwood forests and swamps. This species is highly connected to water. Southeastern myotis are known to roost in a variety of habitats such as hollow trees with large cavity openings, caves, bridges, culverts, or mines. They also occasionally use buildings and other human structures. As many as 2,000 – 3,000 mothers and pups have been found in bridges and culverts (Keeley and Tuttle 1999). They have been documented using both open spaces and crevices underneath concrete bridges in at least four states within their range. 

Southeastern myotis are reported to forage over narrow, slow-moving creeks adjacent to upland loblolly pine, shortleaf pine, stand of hardwoods, and narrow beech magnolia bottoms. Most records of this species are from the southern extent of the Upper Coastal Plain and Lower Coastal Plain of Georgia. Scattered records of this species are known from the Piedmont and Upper Coastal Plain.

Diet

The southeastern myotis captures prey in flight i.e., aerial hawking, and their diet mostly consists of mosquitoes and crane flies but may also include moths and beetles. They are also known to consume trichopterans (caddisflies).

Life History

The timing of mating in southeastern myotis is believed to occur in Autumn, and approximately, 90% of females give birth in late April or mid-May. This species is unique and usually gives birth to twins. The young are more altricial than other species and experience higher mortality during the first few weeks of life. The young are capable of flight at five to six weeks old and maternal roosts are usually in caves or basal tree hollows that contain water. Maternity colonies can be large, often containing over 100 individuals. Maternity colonies of southeastern myotis prefer roosting in mature, live hollow trees that possess large basal openings, primarily black gum, water tupelo, American sycamore, sweetgum, Nuttall oak, and more. Rice 1957 found that males represented 18% of the nursery colonies. The largest colonies have been documented roosting in Florida caves, estimating at 190,000 individuals in seven maternity sites. This number is 50% lower than in the 1950s. Georgia has a few colonies remaining in cave habitats in the southeastern portion of the state. 

In the northern part of their range, hibernation occurs in the winter. During hibernation, southeastern myotis form tight clusters, hanging from ceiling and walls in caves, buildings, culverts, tree cavities. This species arouses more easily than other species. In the northern part of their range, this species hibernates for up to seven months but in the southern part of their range including Georgia, they tend to have less fat reserves and remain active throughout the winter. Winter and summer roost sites can differ but some have been observed in the same roost sites all year long. Roost-switching was also documented by Reed 2004 in Arkansas by males.

Survey Recommendations

Summer mist net surveys should be done close to water and in habitat that is associated with this species. Mist netting surveys in Georgia should follow guidelines laid out on our Bat Survey Guidance webpage (http://www.georgiawildlife.com/BatSurveyGuidance). Mist net and cave surveys (especially during winter months) should be done with care to prevent the spread of the causative fungus of white-nose syndrome (WNS). Avoid the spread of WNS by decontaminating all survey gear and clothing (https://www.whitenosesyndrome.org/static-page/decontamination-information).

Range

Southeastern myotis ranges throughout the southeastern United States. The range extends from southeastern North Carolina to central Florida, across southeastern states to eastern Texas and Oklahoma, and northward up the Mississippi River Valley to western Kentucky, southern Illinois, and South Indiana. This species is mostly absent from the piedmont physiographic regions in North and South Carolina and from uplands of Arkansas.

Threats

Population declines have been documented throughout their range due to loss, fragmentation and degradation of bottomland hardwood forests. Remaining bottomland hardwood forests continue to be fragmented due to drainage, levee constructions, reservoir creation, improved road access, increased agricultural use, and urban development. Tropical storms and hurricanes have contributed to habitat loss and change for these species. Climate change and the possibility of drought present additional, yet unknown challenges. Human disturbances during hibernation can arouse bats and cause them to deplete fat reserves. An emerging threat to this species is white-nose syndrome (WNS), caused by the invasive fungus, Pseudogymnoascus destructans (PD).

Georgia Conservation Status

With declining populations and recent threats, this species is listed as a SWAP High Priority mammal. Although US Fish and Wildlife lists this species as a “species of concern” there are no state-level protections for this species.

Conservation Management Recommendations

Protection of occupied caves and preservation and management of summer foraging habitat, especially wetlands and bottomland forests. Determining suitable habitat and roosting locations are key to preserving their winter and summer roosting areas. Preventing the spread of WNS is also critical for the future survival of this species.

References

Bat Conservation International and Southeastern Bat Diversity Network. 2013. A conservation strategy for Rafinesque’s big-eared bat (Corynorhinus rafinesquii) and southeastern myotis (Myotis austroriparius). Bat Conservational International, Austin, TX.

Bender, M. J. And D. Parmley. 2008. Noteworthy Records of Bats from Central Georgia. Southeastern Naturalist. 7(4):619-626.

Hermanson, J., K. Wilkins. 1986. Pre-weaning mortality in a Florida maternity roost of Myotis austroriparius and Tadarida brasiliensis. Journal of Mammalogy. 67:751-754.

Morgan, C. N., L. K. Ammerman, K. D. Demere, J. B. Doty, Y. J. Nakazawa, and M. R. Mauldin. 2019. Field identification key and guide for bats of the United States of America. Museum of Texas Tech University. 

Reed, W. D. 2004. Roosting ecology by southeastern myotis (Myotis austroriparius) in southwest Arkansas with emphasis on the U.S. Army Corps of Engineers’ Lake Greeson project area. MS thesis, Arkansas State University, Jonesboro, Arkansas. 

Reid, F. A. 2006. Mammals of North America. Houghton Mifflin Company, New York.

Rice, D. W. 1957. Life history and ecology of Myotis austroriparius in Florida. Journal of Mammalogy 38:15-32.  

Schmidly, D. J., K. Wilkind, and R. H. Weynard. 1977. The bats of east Texas. Texas Journal of Science 28:127-144. 

Sherman, H. 1930. Birth of the young Myotis austroriparius, Journal of Mammalogy. 11:495- 503.

Species Profiles: Myotis austroriparius. Bat Conservation International. Accessed on 9 Jan 2019 from http://www.batcon.org/resources/media-education/species-profiles/detail/1693

Whitaker, J., W. Hamilton. 1998. Mammals of the Eastern United States. Ithaca, New York: Cornell University Press.

Authors of Account

Kaitlyn Torrey

Date Compiled or Updated

K. Torrey: Nov. 2018: original account

S. Krueger: March 2020: updated for final review