205.

Pallid Bat

Antrozous pallidus

French: Antrozon blond / German: Fahlfledermaus / Spanish: Antrozo palido

Taxonomy. Vespertilio pallidus Le Conte, 1856,

“Cahfornia,” USA.

Six subspecies are recognized.

Subspecies and Distribution. A.p.pallidusLeConte,1856—SWCanada(BritishColumbia),USA,andMexico.

A.p.bunker:Hibbard,1934—KansasandOklahoma,CUSA.

A.p.koopmaniOrr&Silva-Taboada,1960—Cuba.

A.p.minorG.S.Miller,1902—SWUSA(CaliforniaandSWArizona)andNWMexico(BajaCalifornia).

A.p.pacificusMerriam,1897—PacificcoastofUSA.

A. p. packardi C. O. Martin & Schmidly, 1982 — N & C Mexico.

Descriptive notes. Head—body ¢.57-82 mm, tail 35-53 mm, ear 21-37 mm, hindfoot 11-16 mm, forearm 45-60-2 mm; weight 14-29 g. Females appear to be slightly larger than males. Fur woolly (dorsal 5-9 mm, ventral 4-8 mm); dorsally creamy yellow to light brown, ventrally very pale to white. Ears large and separate, extending well beyond muzzle when laid forward; tragus long and lanceolate, extending more than onehalf length of pinna. Muzzle is bare and squarely truncate, with low, horseshoe-shape ridge dorsally; has glands that emit a strong odor. Eyes large. Membranes mummy brown. Skull is large (greatest skull length 18-6-23-6 mm); braincase high; rostrum more than one-half as long as braincase; basisphenoid pits absent; tympanic ring large, covering most of cochlea. Dental formula is 11/2, C 1/1, P 1/2, M 3/3 (x2) = 28. Chromosomal complement has 2n = 46 and FN = 50, with three metacentric autosomes, three submetacentric chromosomes, 19 pairs of acrocentric, a submetacentric X-chromosome and an acrocentric Y-chromosome.

Habitat. Mostly arid and semiarid environments, especially desert regions with rocky outcrops, particularly near water, at elevations up to 2440 m. Seems to forage over open habitats, such as scrublands, sparsely vegetated grasslands, and agricultural fields; also found in oak and pine forests.

Food and Feeding. Arthropods, especially orthopterans, coleopterans, and solifugids; a wide variety of prey consumed, including many spiders, scorpions, and occasionally vertebrates (small lizards, rodents, and bats). Pallid Bats capture prey on ground and in flight within a few meters of ground or from surfaces of vegetation. The species has been observed foraging 15-90 cm aboveground and when prey is located,it abruptly drops to the ground, searches briefly, grabs its prey with its mouth, and takes off. Captured prey is taken to a feeding station whereit is consumed. Diet shifts seasonally with common prey availability; there is also geographic variation in diet. The species visits flowers and is a pollinator of several species of cactus;it is the only vespertilionid to feed on nectar, and seems to be opportunistic visitor to flowers and fruits, feeding on insects found within.

Breeding. In California, copulation occurs from October to December, but can extend to February in other localities. Copulation occurs on horizontal surfaces and when bats hang upside down. Males approach females from the rear and the uropatagium of the female is pushed to one side. Females store sperm in the reproductive tract until ovulation takes place in spring. Time of embryonic developmentis variable, but probably averages c.9 weeks. In south-western USA, births generally occur in May and June. Females hang upright during parturition, presentation is breech, and young are held in the curled uropatagium. Pallid Bats can give birth to one or two young per litter, with three embryos occasionally recorded; yearling females have single offspring, whereas older females may have twins annually. Lactation may occur from early May through mid-August, and young begin to accept insect food at six weeks, coinciding with development of functional permanent dentition and ability to fly. Females wean young at 6-8 weeks of age. Bats become sexually reproductive at around one year of age. Reproductive period seems to have a strong association with climatic factors.

Activity patterns. Nocturnal, with emergence to forage after sunset; stays in roost longer into the evening than other bat species; time of emergence changes with season. Pallid Bats have three different roosts, with site preference based on thermal factors: day roost is usually a warm, horizontal opening such as attic or rock crevice; night roost is usually in the open, near foliage, and is selected for stable temperature that remains warmer than ambient temperature; hibernation roost is often in human buildings, caves, or cracks in rocks. Other diurnal roosting locations include stacks of burlap sacks, stone piles, and hollows in trees. Echolocation calls sweep from 49 kHz to 26 kHz, with greatest energy at 30 kHz, two harmonics, and maximum duration of 5 milliseconds during the search phase.

Movements, Home range and Social organization. Probably migrates on a limited basis moving locally to deep recesses of mine shafts or caves to avoid cold winter weather. This species goes into hibernation when kept at low ambient temperatures. Occurs in groups of 15-100 bats, but ¢.95% of groups consist of at least 20 individuals. During breeding, maternity colonies without males are formed.

Status and Conservation. Classified as Least Concern on The IUCN Red List. Widespread with expected large population; occurs in a number of protected areas. No evidence of any major decline.

Bibliography. Arroyo-Cabrales & de Grammont (2017a), Frick et al. (2009), Hall (1981), Hermanson & O'Shea (1983), Lenhart et al. (2010), Vaughan & O'Shea (1967), Verts & Carraway (1998), Wilson & Ruff (1999).