395.

South-eastern Myotis

Myotis austroriparius

French: Murin du Mississippi / German: Siidostliches Mausohr / Spanish: Ratonero del Misisipi

Taxonomy. Vespertilio lucifugus austroriparius Rhoads, 1897,

“Tarpon Springs [Pinellas County], Florida,” USA .

Subgenus Pizonyx; albescens species group. Monotypic.

Distribution. SE USA, in S Illinois and S Indiana S to E Texas, and Florida, and E to North Carolina and South Carolina through W Kentucky, W Tennessee, Alabama, and Georgia.

Descriptive notes. Head-body 45-51 mm, tail 26-44 mm, ear 9-16 mm, A 7-12 mm, forearm 33-40 mm; weight 5-8 g. Females are slightly bigger than males. Dorsal hairs vary from grayish brown to bright orange-brown, with bases slightly darker than tips. Ventral hairs are strongly bicolored, with dark brown bases and whitish, grayish brown, or yellowish brown tips. Females are generally more brightly colored than males; color variation can depend on molt that is correlated with reproductive stage. Ammonia steam in large cavesalso affects fur color. Ears are medium-sized to large, extending forward halfway from eye to nostril, and tragus is short and blunt. Nose is bare and pinkish. Membranes are mummy brown or blackish; plagiopatagium is broadly attached to foot at base of toes. Calcar is not keeled, and toes have long hairs, extending beyond tips of claws. Fur is short, thick, and woolly. Skull is small to medium-sized (greatest length of skull 13-5-15- 2 mm); forehead rises abruptly; braincase is highly inflated; and medium sagittal crest can be felt through skin. Chromosomal complement has 2n = 44 and FN = 50, with 17 pairs of acrocentric and four pairs of metacentric autosomes. X- and Y-chromosomes are submetacentric.

Habitat. Mainly Gulf coastal plain in riparian floodplain forests or wooded wetlands with nearby permanent open water such as lakes, ponds, or slow-moving streams.

Food and Feeding. The South-eastern Myotis emerges after dark and usually forages within 60 cm of water surfaces, capturing small insects in flight. Coleoptera, Lepidoptera, and Diptera occurin diets; it eats midges, mosquitoes, small moths, small beetles, and cane flies.

Breeding. All male South-eastern Myotis from Florida had enlarged epididymides from about mid-February to mid-April. In Indiana, males with scrotal testes ware reported in March-April and August (largest testes in August). In Florida, mating is from mid-February to mid-April; altricial young are most frequently born from late April to the end of May, with births peaking in mid-May. Young were found as early as 30 April, and no pregnant females were detected after 17 May. Ninety percent of pregnant females give birth to twins (one from each uterus); it is the only species of Myotis known to have twins. Delayed fertilization does not occur in Florida. During birth, a mother forms a receptacle with the uropatagium to catch her young. Placenta does not appear until several hours after birth, and the mother pulls it out with her teeth and eats it. Births generally occur during the day. Neonates are born naked, with their eyes and ears closed, and weigh slightly more than 1 g. Pre-weaning mortality is high, which might suggest that twinning is adaptive. Because South-eastern Myotis usually roosts in caves with water, many neonates fall and drown. Young can fly at 5-6 weeks old. Maternity colonies are formed during mid-March and early April, and they contain 2000-90,000 individuals. Young grow rapidly; both sexes reach sexual maturity before one year of age.

Activity patterns. South-eastern Myotis consistently emerge from roosts in complete darkness, generally later than other species of Myotis . Pattern of nocturnal activity is not well understood, but evidence suggests bimodal activity, with foraging peak after sunset and anotherjust before dawn. It uses caves asits primary roosts, especially those containing pools of water. It also roosts in human habitations and structures such as attics, barns, bridges, culverts, storm sewers, boat houses, and mines; under bark; or in hollow trees (e.g. Nyssa, Nysaceae; Carya, Juglandaceae; Taxodium, Cupressaceae). Most maternity colonies are in caves but sometimes in buildings. In some regions, different roosts are used in summer and winter; Kentucky populations use caves in winter but are rare in most caves in summer when large hollow trees are used. High humidity and constant warm temperatures are key characteristics of maternity sites.

Movements, Home range and Social organization. South-eastern Myotis are not known to migrate. Patterns of movements between summer and winter roosts are largely unknown, but banded individuals moved 29-72 km. In northern parts of the distribution, individuals hibernate almost all winter and have been found in compact clusters of up to 50 individuals hanging from ceilings and walls of caves or beneath buildings. These individuals went into semi-torpor when temperatures dropped below 4°C, but when warm temperatures returned, they awoke and resumed nightly foraging activities. In the northernmost distribution, hibernation can last up to seven months from September— October to February-March. In southern parts of the distribution, individuals remain active throughout much of the winter, foraging actively at night. Maternity colonies can contain a few hundred to thousands of individuals. Few males are found in maternity colonies, but many adult males joined maternity colonies after young have matured. Males generally roost alone or in small bachelor groups. South-eastern Myotis occasionally share roosts with Rafinesque’s Big-eared Bats ( Corynorhinus rafinesquii), Gray Myotis (M. grisescens), Little Brown Myotis ( M. lucifugus),, Indiana Myotis ( M. sodalis), Tricolored Bats ( Perimyotis subflavus), and Brazilian Free-tailed Bats (Tadarida brasiliensis).

Status and Conservation. Classified as Least Concern on The IUCN Red List. The Southeastern Myotis widespread and presumably has a large population. Nevertheless, studies indicate the need for population monitoring due to increased caves exploitation and spread of White-nose Syndrome caused by a fungus pathogenic to species of Myotis .

Bibliography. Arroyo-Cabrales & Alvarez-Castaneda (2017f), Baker & Patton (1967), Gardner etal. (1992), Gomoll (2004), Gore & Hovis (1992), Hobson (1998), Horner & Mirowsky (1996), Jones & Manning (1989), LaVal (1970), Miller & Allen (1928), Munford & Whitaker (1982), Rice (1957), Simmons (2005), Whitaker & Hamilton (1998), Wilson & Ruff (1999).