Thursday, August 20, 2009

pallid bat field note

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Pallid Bat Wildlife Field Notes  ■  Antrozous pallidus  ■  By Angie McIntire Illustration by Zackery Zdinak Scientific Name: Antrozous pal-lidus. Its name comes from the Greek antro meaning “cave,” and zous mean-ing “animal;” and from the Latin pallidus,meaning “pale.” This bat also is referred to as the “desert bat.” Description: A relatively large bat with a forearm length of 45 to 60 mm, the pallid bat is light in color with long, prominent ears and pinkish-brown or gray wing and tail membranes. Adults usually weigh 17 to 28 grams (about the weight of six nickels). The pallid bat can be distinguished from other bats by its yellowish or cream-colored fur, large ears and the presence of a small horseshoe-shaped ridge on its blunt muzzle. Glands near its nostrils secrete a distinct skunk-like scent, possibly used as a defense. Distribution: The pallid bat ranges across western North America from south-central British Columbia to central Mexico. It is found throughout Arizona in the sum-mer at elevations ranging from 210 to 6,850 feet, but limited to southern parts of the state during the winter. Habitat: The pallid bat is most abundant in dry ecosystems, including the Great Basin, Mohave and Sonoran deserts, but it can be found in a variety of habitat types, including oak and pine forest, rocky canyons, farmlands and scrub grassland. Day and night roost types include crevices in cliffs, mines and rocky outcrops. This species also will roost in hollow trees, bridges, barns, porches and bat houses. Biology: The pallid bat com-monly roosts in groups of 20 or more, but may roost alone, in small groups of two to 20 bats, or gregariously (with hundreds of individuals). Pallid bats also will roost with bats of different spe-cies. They appear to be highly social, with distinct vocalizations to com-municate about orienting, irritation and spacing within the roost. Mating occurs throughout the winter and females begin to form nurs-ery colonies in April. Young are born over a two-week period in late May or June. A female pallid bat typically has one or two pups per year. Young bats reach adult size in five to seven weeks, but do not attain adult weight until the follow-ing year. While most bats in Arizona are known to feed on the wing, the pallid bat mostly consumes insects it plucks from foliage or the ground. It can consume up to half its weight in insects every night. It may echo-locate while foraging, but also uses passive sound to home in on its targets. Its flight style consists of dipping, rising and swoop-ing as it forages a few feet from the surface in search of cicadas, crickets, beetles, scor-pions, centipedes and the occasional gecko, lizard or small rodent. In a typical evening, the pallid bat has two foraging periods with an intervening rest period. Status: This common bat apparently adapts to a variety of habitat conditions. Short- and long-term trends appear to be stable and it is not a species of concern in Arizona. However, the pallid bat may be susceptible to disturbance at its roosts, and should be monitored for impacts from ongoing habitat loss due to urbanization. Management Needs: We lack data on the impacts of pesticides for this species and its winter habits are poorly understood. Information in these areas, as well as investigation of the pallid bat’s use of dif-ferent resources in diverse habitats, will increase the effec-tiveness of management actions. The Arizona Bat Conservation Strategic Plan outlines goals and objectives for managing, monitoring and researching the pallid bat and Arizona’s other bat species. ■  Nongame biologist Angie McIntire developed a passion for bats as a department intern. The first bat she ever met was a pallid bat. While most bats in Arizona are known to feed on the wing, the pallid bat mostly consumes insects it plucks from foliage or the ground. November–December 7 ■ A R I Z O N A   W I L D L I F E   V I E W S  17

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