169.

Silver-haired Bat

Lasionycteris noctivagans

French: Sérotine argentée / German: Silberhaarfledermaus / Spanish: Lasionicterio argentado

Other common names: Black Bat, Silver Bat, Silverblack Bat, Silvery-haired Bat

Taxonomy. Vespertilio noctivagans Le Conte in McMurtrie, 1831,

Eastern United States.

Lasionycteris has been considered similar to Myotis and has become specialized by the loss of P°. Based on bacular morphology and molecular reconstructions, relationship of L. noctivagans with Myotis is more distant than previously thought. Monotypic.

Distribution. SE Alaska S to Canada along Pacific coast and extending along lower one-third of Canada; widely distributed in the USA, with exception of SW & SE coasts, with S limit in NE Mexico (Sierra de San Carlos).

Descriptive notes. Head-body ¢.57-70 mm, tail 35-45 mm, ear 8-10 mm, hindfoot 7-9 mm, forearm 37-44 mm; weight 8-1-11 g. The Silver-haired Bat is characterized by presence ofsilver to white tips on black fur, dorsally and ventrally, being less pronounced on ventral fur. Fur tips can be yellowish or absent in older adults. Fur on head is darker, and basal one-half of uropatagium is densely furred above. Wings, uropatagium, and ears are black. Ears are short, naked, and rounded. Tragus is broad and blunt. Baculum is comparatively large among vespertilionids; base is swollen, tapering to cylindrical shaft with slightly thicker distal end; distal end is bilobed; and baculum extends well into corpus cavernosum. Skull is flattened, and rostrum is broad; sagittal crest is obsolete; interorbital region is wide and flattish; and uppersurface of rostrum is distinctly concave on each side between lacrimal region and nares. Additional general features of skull and structure of teeth are as in Myotis . I? is strongly bicuspidated,; M? has more than one-half the crown area of M'; and metaconeis slightly smaller than paracone with well-developed commissures. Dental formula is I 2/3, C 1/1, P 2/3, M 3/3 (x2) = 36. Chromosomal complement has 2n = 20 and FN = 28, which is significantly distinct from all other species of vespertilionids.

Habitat. Primarily forest habitats, such as boreal or coniferous, temperate deciduous, and old growth forests; grasslands; and near water at elevations of 152-563 m in West Virginia and 1360-1965 m in South Dakota. The Silver-haired Bat is adapted to edge habitats and cannot forage in closed habitats.

Food and Feeding. Insectivorous. Diets vary throughoutits distribution, depending on time ofyear and prey availability. Feces from Idaho contained mainly Lepidoptera, Homoptera, Coleoptera, and Diptera . In coastal wet forests, diets mostly contain dipterans. Stomach samples from Indiana contained 90-100% Trichoptera. Feces from New Mexico suggested specialization on moths. These bats forage over small ponds and streams or on treetops. They are relatively slow fliers, foraging on hunting routes of 46-91 m in diameter, and fly erratically taking many twists and frequent short glides.

Breeding. The Silver-haired Bat is polyandrous. Mating occurs in autumn; females store sperm in winter. Gestation lasts 50-60 days;littersize is typically two young. Newborns are hairless, with pink skin and dark membranes; ears are folded; and eyes are closed. Sexual maturity is achieved at 145-160 days. Newborns were recorded in late June in Iowa and earlyJuly in upstate New York;juveniles were captured in late July.

Activity patterns. The Silver-haired Bat forages right before and shortly after sunset, later on night, and also close to dawn. In Iowa and Montana,first and major peak activity occurs 2-4 hours after dark and 6-9 hours after dark. Day roosts are mainly under loose bark of trees but also in cavities. Hibernation occurs in October—-March, and hibernating bats roost in mines, caves, hollow trees, and houses and under loose bark. Echolocation calls are FM. Search-approach calls are FM with CF tail, last an average of 9-4 milliseconds, and sweep from 46 kHz to 26 kHz. Tracking calls are similar, tending to be shorter with higher initial frequencies. Terminal calls are also FM and reach minimum duration of 1 millisecond and minimum frequency of 18 kHz.

Movements, Home range and Social organization. The Silver-haired Bat is believed to be solitary. Females form small maternity colonies during reproductive seasons. Despite their solitary habit, small groups were observed in warm months. Males and females spend summer months at separate locations and reunite in swarms during migration in autumn. Due to migration, local abundance varies within seasons; northward shifts on their distributional limits are noticed in spring and southward shifts in autumn. In spring, eastern populations seem to disperse east and north, and western populations disperse north. In autumn, populations tend to shift south.

Status and Conservation. Classified as Least Concern on The IUCN Red List. In Mexico, the Silver-haired Batis listed as subject of special protection.

Bibliography. Adams & Pedersen (2013), Baker & Patton (1967), Barclay (1985, 1986), Bentley (2017), Black (1974), Cryan (2003), Frum (1953), Hall (1981), Hamilton (1949), Jones, Lampe et al. (1973), Kunz (19734, 1982b), Lacki et al. (2007), Mattson et al. (1996), Ortega & Arita (2014d), Patriquin & Barclay (2003), Simmons (2005), Whitaker (1972), Wilson & Ruff (1999).