376.

Little Brown Myotis

Myotis lucifugus

French: Murin brun / German: Kleines Nordamerika-Mausohr / Spanish: Ratonero marrén pequeno

Other common names: Little Brown Bat

Taxonomy. Vespertilio lucifugus Le Conte in McMurtrie, 1831,

type locality not given. Restricted by G. S. Miller, Jr. in 1897 to “Georgia, probably southern Liberty County,” USA.

Subgenus Pyzonix; lucifugus species group. See M. evotis . Phylogenetic and gene flow analyses with mitochondrial and nuclear genes provide evidence that subspecies of M. luctfugus are paraphyletic, exchange alleles with other species of Myotis in regions of secondary contact, and should be considered independent evolutionary lineages despite their morphological similarity. These issues remain unresolved. Five subspecies recognized.

Subspecies and Distribution. M.l.lucifugusLeConte,1831—NorthwestTerritories(Canada)throughoutEsea-boardtoNFlorida(USA),andwhereothersubspeciesdonotoccur.

M.l.alascensisG.S.Miller,1897—AlaskathroughBritishColumbiaandSintoPacificNWUSA.

M.l.carissimusThomas,1904—C&WUSA,exceptforcoastalregions.

M.l.pernoxHollister,1911—restrictedtoCborderarebetweenBritishColumbiaandAlberta(WCanada).

M. l. relictus A. H. Harris, 1974 — mountains of California (SW USA).

Descriptive notes. Head-body ¢. 32-53 mm, tail 28= 49 mm, ear 11-15 mm, hindfoot 8-10 mm, forearm 33-1-41- 4 mm; weight 5-12 g. The Little Brown Myotis is morphologically similar to its Neotropical congeners. Fur is long, silky, and glossy. Dorsal hairs range from dark brown, golden brown, reddish, to olive brown, with bases darker than tips. Ventral hairs are lighter, with dark brown bases and pale yellowish tips. Ears are comparatively short, extending forward halfway from eye to nostril. Tragus is medium in height (length 7-9 mm) and blunt. Membranes are mummy brown or blackish; plagiopatagium is broadly attached to foot at base of toes. Calcar has no keel; tibia is short relative to length of hindfoot. Skull is moderate in size (greatest skull lengths 14-15- 9 mm); rostrum is shortened; forehead has upslope profile; braincase is flattened and subcircular when observed dorsally; sagittal crest is absent; and lambdoidal crests are absent or, when present, very low. Chromosomal complement has 2n = 44 and FN = 50, with four metacentric or submetacentric and 17 acrocentric pairs of autosomes. X- and Y-chromosomes are submetacentric.

Habitat. Temperate coniferous forests, lowland temperate grasslands, savannas and shrublands, deserts, tundra, boreal forests and taiga, and temperate broadleaf forests. The Little Brown Myotis is most associated with forested areas near water.

Food and Feeding. The Little Brown Myotis catches prey by aerial hawking and gleaning. It prefers foraging on swarms of insects. Individuals usually return to areas where they have had prior feeding success. Differentstrategies of prey selection can be applied according to insect availability. In large swarms of insects, they concentrate on 1-2 species, but when insects are dispersed, they are less selective and consume multiple species. They generally select insects of 3-10 mm long, but pregnant females usually select larger insects. They typically eat one-half of their body weight each night, but lactating females eat c.110% of their body weight per night. They catch free-flying insects in wooded areas, fields, and over water bodies and also insects on the water surface. Midges ( Diptera) are the primary food sources, but a large part of their diet comes from other aquatic insects, such as caddisflies (Trichoptera) and mayflies (Ephemeroptera). When available, beetles ( Coleoptera), moths ( Lepidoptera), and lacewings ( Neuroptera) are eaten.

Breeding. Breeding of Little Brown Myotis occurs in late summer and autumn, at night, and in hibernacula. During late July, adult males and non-parous females arrive at hibernacula. Females and subadults appear in early August. Mating occurs in two phases, active and passive. During the active phase, both partners are awake and alert. In the passive phase, active males mate with torpid individuals of both sexes (c.35% of passive phase mating is homosexual). Little Brown Myotis is polygynandrous, and females in active phase usually mate with more than one male. In active and passive phase mating, males mate with multiple females. Mating behavior begins when a male mounts a female from the rear and bites her back. If the female struggles, the male might emit a copulation call to ease the female. Females store sperm in their uteri through autumn and winter and ovulation and fertilization occursin spring (c.7 months after copulation). Females tend to congregate in nursery colonies, gestation lasts 50-60 days, and females give birth to one young thatis reared June-July. Timing of births varies from north to south and from higher to lower elevations. Neonates weigh ¢.25% of their mothers’ body weights. In the first 18 days, young ingest only milk. After, insects are included in the diet. Three weeks after birth, young are able to fly, but independence occurs at about four weeks of age when adult weightis reached. Males are not sexually mature until after their first year, and spermatogenesis starts in May and ends in August.

Activity patterns. Little Brown Myotis are nocturnal and emerge from their roosts at dusk. Night activity occurs in two peaks: c.2-3 hours after dusk and before dawn. They usually enter daily torpor. In winter, hibernation time depends on altitude and location of roosts. It usually starts in September—November and ends in March—-May. Young remain active longer in autumn to build fat deposits to last the winter. There are three types of roosts: day, night, and hibernation roosts, and selection is taken based upon the presence of stable ambient temperatures. Day and night roosts are used by active bats and include buildings, trees, under rocks, and piles of wood. Day roosts have low luminosity and typically have south-western exposures to provide heat for arousal from daily torpor. Night roosts usually are confined spaces where large concentrations of individuals can cluster together to increase temperature in the roost. These roosts are primarily occupied when temperatures are less than 15°C. Night roosts are usually away from day roosts. Hibernation roosts include mainly abandoned mines or caves where temperature is continuously above freezing and humidity is high. Little Brown Myotis produce FM calls at 45 kHz. Calls last 1-5 milliseconds and sweep from 80 kHz to 40 kHz. Moving individuals produce c.20 calls/ second to detect prey and objects.

Movements, Home range and Social organization. Home ranges of Little Brown Myotis vary according to sex, reproductive condition, and geographical location. In New York, mean home range of both sexes was 143 ha. In Quebec, Canada, female home range averaged 30-1 ha during pregnancy and 17-6 ha during lactation. In New Brunswick, Canada, mean movement of males between roosts was 275 m, with mean minimum roosting areas of 3-9 ha, mean minimum foraging areas of 52 ha, mean distance between roosting and foraging areas of 254 m, and mean distances between capture sites and first roosts of 761 m. In western Montana, USA, average daily movement between roosts was 970 m (range 35-5154 m). Little Brown Myotis spend winter hibernating in underground sites such as caves or abandoned mines and can make long-distance migrations of up to 1000 km between summer and winter roosts. Northern populations enter hibernation in early September and arise in mid-May. Southern populations enter hibernation in November and arise in mid-March. They are not territoriality in roosts, and large colonies of as many as 300,000 bats have been reported in a single roost. Hibernacula can be shared with other bat species, such as the Yuma Myotis (M. yumanensis).

Status and Conservation. Classified as Endangered on The IUCN Red List. It is expected that the total number of mature Little Brown Myotis will decline by more than 50% over the next three generations due to White-nose Syndrome, a fungal disease caused by an introduced pathogen. The disease has been expanding at an average rate of 200-250 km /year. At that rate, the entire population of Little Brown Myotisis likely to be affected within 12-18 years. There is no apparent containment of northward or westward spread of the disease, and proper growing conditions for the fungus exist throughout the remaining distribution of the Little Brown Myotis .

Bibliography. Anthony & Kunz (1977), Barbour & Davis (1969), Belwood & Fenton (1976), Broders et al. (2006), Coleman et al. (2014), Fenton & Barclay (1980), Fenton & Bell (1979), Frick et al. (2010), Hall (1981), Henry et al. (2002), Morales & Carstens (2018), Norquay et al. (2013), Ratcliffe & Dawson (2003), Schowalter (1980), Schwab (2006), Simmons (2005), Solari (2018n), Wilson & Ruff (1999).