Silver-haired bat

Silver-haired bat
Male silver-haired bat captured in the Ozark National Scenic Riverways in 2010.
Conservation status
Least Concern  (IUCN 3.1)[1]
Scientific classification
Kingdom:	Animalia
Phylum:	Chordata
Class:	Mammalia
Order:	Chiroptera
Family:	Vespertilionidae
Genus:	Lasionycteris
Species:	L. noctivagans
Binomial name
Lasionycteris noctivagans (Le Conte, 1831)
Distribution of the silver-haired bat (2009)

The silver-haired bat (Lasionycteris noctivagans) is a solitary migratory species of vesper bat in the family Vespertilionidae and the only member of the genus Lasionycteris.^[2]

Etymology

The species name translates as night-wandering, referring to the nocturnal behavior of bats.

Description

This medium-sized bat is predominately black (including the wings, ears, interfemoral membrane, and fur) with white-tipped hairs. The basal upper half of its tail membrane is densely furred. This gives the bat a frosted appearance and its common name's sake. This species has a flattened skull with a broad rostrum.^[3] This species weighs around 8–12 g, has a total length of ~100 mm, a tail length of 40 mm, and a forearm length of 37–44 mm.^[4]

Distribution and habitat

Lasionycteris noctivagans is found in Bermuda, Canada, Mexico, and the United States. This forest inhabitant is known to occur from southeastern Alaska in summer to northeastern Mexico in winter ^[5] and is found in xeric habitats at low elevations during seasonal migrations. In Missouri, reproduction occurs in the northern dissected plains region, but reproductive females are believed to be absent from the southern Ozark highlands in the summer.

They often roost in tree cavities or in bark crevices on tree trunks, especially during migration. Their unique coloration makes them blend in with their roosting environment.^[6]

Life history

Copulation of tree bats is likely initiated during flight. After mating, tree bats hibernate alone in tree cavities, bark crevices, beneath leaf litter, or in the twilight zone of caves. Gestation typically takes 50–60 days, so that parturition of pups occurs in early summer when insect availability is high.^[7] Pups are born breech by presentation, and the mother consumes the placenta ^[8] Females typically give birth to two offspring, with an even sex ratio.

Diet and foraging behavior

Silver-haired bats consume primarily soft-bodies insects, such as moths, but will also take spiders and harvestmen. This species will forage low, over both still and running water, and also in forest openings. Silver-haired bats are slow but maneuverable flyers that typically detect prey a short distance away.^[9]

Conservation threats

In addition to the hoary bat (Lasiurus cinereus) and eastern red bat (Lasiurus borealis), the silver-haired bat is one of the three tree bat species most commonly killed at wind energy facilities (over 75% of the mortalities).^[10]

The causative agent of white-nose syndrome, Pseudogymnoascus destructans, has been detected on a silver-haired bat in Delaware, although this species does not suffer the same mass moralities observed in smaller-bodied hibernating North American cave bats.^[11]

Like all bats, silver-haired bats are vulnerable to population threats because of their inherently low reproductive rate.^[12]

Rabies

Most bats do not have rabies. However, most recent human rabies deaths have been due to a strain of rabies associated with this species.^[6]

Trivia

Shade from Kenneth Oppel's novel Silverwing (novel) is most likely loosely based on the colonial Indiana bat (Myotis sodalis) which is silver-gray in color both dorsally and ventrally. Pregnant Indiana bats gather together in large maternity trees to reproduce in during the summer, and nurse their young (one offspring is born to each female although actual survival rates of neonates are roughly 0.9 pups/female). Indiana bats demonstrate strong site fidelity, returning to the same maternity colony year after year (unless the tree is felled to clear land for human development). In the fall, mothers and young migrate back to the same winter hibernaculum (cave) where they will gather in large numbers (into the hundreds of thousands), and are joined by adult males. Mating occurs at this time, in an event called "swarming" during which mating occurs both on the wing, while roosting, in trees, and on the ground at the entrance of the hibernaculum. Whereas most mammals conceive shortly after copulation, female bats in temperate regions exhibit delayed fertilization. After swarming, this species enters hibernation within the cave, and females store viable spermatozoa throughout the hibernation period, for up to six months. When spring arrives, females arouse from hibernation, and become pregnant (females ovulate and spermatozoa become motile). Little brown bats (Myotis lucifugus) have a nearly identical life history, and also reproduce together in the same maternity tree (although this species will also use a building) during the late spring and early summer. In the winter, little brown bats gather together in large hibernaculum (cave or building), frequently sharing their hibernation site (if it's a cave) with gray bats and Indiana bats. Other species in this series may be based on the colonial gray bat (Myotis grisescens). Unusually for North American bats, gray bats are cave obligates, and need maternity caves to reproduce in during the summer. Hundreds of thousands of gray bats will hibernate in a single large hibernaculum, whereas solitary, black winged, migratory silver-haired bats overwinter alone in tree bark, rock crevices, building's, and occasionally in crevices within the twilight zone of caves.

See also

• Bats of Canada

References