178.

Big Brown Bat

Eptesicus fuscus

French: Sérotine brune / German: Grol 3e Braune Breitfligelfledermaus / Spanish: Eptesicus bruno

Taxonomy. Vespertilio fuscus Palisot de Beauvois, 1796,

Philadelphia, Pennsylvania, USA.

Eptesicus as currently defined is paraphyletic with respect to Histiotus, which is closely related to the New World Eptesicus . Histiotus is recognized as a distinct genus here based on its morphological distinctions, and Eptesicus will likely be split into multiple genera in the near future to avoid paraphyly. Eleven subspecies currently recognized.

Subspecies and Distribution.

E.f.fuscusPalisotdeBeauvois,1796—SECanadaandEUSA.

E.f.bahamensisG.S.Miller,1897—Bahamas(NewProvidenceandSanSalvadorIs).

E.f.bernardinusRhoads,1902—SWCanada(BritishColumbia)andWUSA.

E.f.dutertreusP.Gervais,1837—Bahamas(Andros,Exumas,Long,Crooked,andAcklinsIs),Cuba,andCaymanIs(CaymanBrac).

E.f.hispaniolaeG.S.Miller,1918—JamaicaandHispaniola.

E.f.miradorensisH.Allen,1866—mostofMexico,CentralAmerica,andAndesofWVenezuela,NColombia,andNEcuador.

E.f.osceolaRhoads,1902—-Florida,SEUSA.

E.f.pallidusYoung,1908—WCCanada,C,WC&SWUSA,andNW&NCMexico.

E.f.peninsulaeThomas,1898—BajaCaliforniaSur,NWMexico.

E.f.petersoniSilva-Taboada,1974—IsladelaJuventud(Cuba).

E. f. wetmorei H. T. T. Jackson, 1916 — Puerto Rico, Dominica, and Barbados.

Descriptive notes. Head-body ¢.53-82 mm, tail 34-56 mm, ear 10-20 mm, hindfoot 8-14 mm, forearm 39-54 mm; weight 11-23 g. Females are slightly larger than males. Fur is of the Big Brown Bat long, soft, and fairly oily. Dorsal fur is generally brownish, varying from pinkish tan to rich chocolate; longer hairs have shiny tips. Ventral fur is paler, varying from near pinkish to olive buff. Ears are short, rounded, and furred on medial sides of bases; tragus is broad. Face and nose are wide. Face, ears, and membranes are black and naked, contrasting with body. Uropatagium has scarce hairs on basal one-fourth. Skull is large and heavy; rostrum is rounded and fairly flattened; and palatal emargination is at least as deep as wide. Upper incisors are large; I? is heavy, usually with distinctive secondary cusp; C' is separated from I’; lower incisors are trifid and crowded; I, is wider than I, and L; crowns of M! and M? are narrower than in M3; and hypocones on M' and M? are obvious. Dental formula for all species of Eptesicus is 12/3,C1/1,P 1/2, M 3/3 (x2) = 32. Chromosomal complement has 2n = 50 and FN = 48, with acrocentric autosomes and Y-chromosome and submetacentric X-chromosome.

Habitat. Open to forested areas including evergreen forests, cloud forests, scrublands, grasslands, temperate forests of pine and oak, tropical deciduous forests, rural areas, and cities at elevations of 300-3466 m.

Food and Feeding. The Big Brown Bat is insectivorous. Flying speeds are up to 33 km /h, foraging c.100 minutes/night. Flying heights vary from 50 m,later descending to 10-15 m in forested areas, to c. 5 m over canopy-enclosed streams. Foraging areas are highly diversified, with no preference for any specific area; they can forage over water, over land, in forest edges, canopy-enclosed areas, above croplands, and along streets. Big Brown Bats mostly eat flying beetles, but various insects also occur in diets (e.g. moths,flies, wasps,flying ants, lacewingflies, and dragonflies). They can capture one insect every three seconds if conditions are good, and they use night roosts to rest and digest food. Stomach contents contained vegetation and non-flying insects (4% by volume). Despite their preference for flying beetles, young seem to prey more frequently on soft-bodied insects.

Breeding. Reproduction of the Big Brown Bat has a unimodal reproduction pattern. Mating occurs in September and ovulation in spring after hibernation. Parturition occurs 60 days later from late April to early July. There are usually 1-2 young/pregnancy. Young start to fly at 18-35 days of age. Females store fat to support fetal growth in late pregnancy. During lactation, amount of fat, ash, and ash-free lean dry tissue declines, but it is restored when lactation ends. Males become sexually mature within their first year, but females might not reproduce in the first year. Most females return to their natal nursery site in the following spring, and ¢.10-30% of young females also return.

Activity patterns. Big Brown Bats are crepuscular and nocturnal. Individuals start leaving roosts well before sunset, but peak activity is mainly 2-3 hoursafter sunset. Despite this, foraging occurs throughout the night. Foraging occurs during dry and warm nights, with temperatures exceeding 10°C; on rainy and cold evenings, individuals tend to stay at roosts and become torpid, and they use fat reserves during unfavorable periods until weather conditions improve. Some populations hibernate in northern parts of the distribution. Hibernation can occur from October to May, but most individuals only appear at hibernacula in November. Hibernation sites are usually inside walls of heated buildings or dry caves with air currents. Big Brown Bats roost in hollow trees, small caves, and man-made structures; maternity colonies have been found in rock crevices and dead ponderosa pines ( Pinus ponderosa, Pinaceae). Echolocation calls include multiple-harmonic FM sweeps, with broadband and narrowband components. In the laboratory, pulses sweep down from 48 kHz to 27 kHz, with durations of 3—4-2 milliseconds in search phase and 0-25-0-6 milliseconds in terminal stage.

Movements, Home range and Social organization. Males are usually solitary in spring and summer, but they can roost with females or other males; adult females gather in maternity colonies of 5-700 individuals. Most colonies, however, have 25-75 adults. Maternity colonies disband in August-September, and individuals hibernate alone or in small groups of up to 20 individuals. Roosting sites and foraging areas are usually within 1-2 km from each other. Individuals migrate ¢. 80 km from summer to winter roosts, and a banded individual moved to a different hibernating roost 350 m away during the same winter.

Status and Conservation. Classified as Least Concern on The IUCN Red List. The Big Brown Bat is found in several protected areas and is somewhat common.

Bibliography. Arguero & Albuja (2012), Baker, R.H. (1983), Baker, R.J. & Patton (1967), Davis & Gardner (2008), Goehring (1972), Hall (1981), Kurta & Baker (1990), Miller et al. (2016c), Nowak (1999), Simmons (2005), Tellez (2014d), Timm & Genoways (2003), Wilson & Ruff (1999).