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Chapter 10: Desserts
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hoary bat 135 1988; Perry and Thill 2007a). Although this species generally has low roost-site fidelity, females have been documented using the same roost for 23–26 consecutive days during the maternity season (Perry and Thill 2007a). Hoary bats have infrequently been found roosting in sites other than tree foliage. These include a squirrel’s nest, the side of a building, underneath driftwood , in a woodpecker hole, under a bridge, and in caves (Bowers et al. 1968; Carter and Menzel 2007; Hendricks et al. 2005; Neill 1952). Individuals in caves are rarely found alive; those that are alive are often extremely weak and emaciated and are unable to fly. Presumably they become disoriented and are unable to find an exit once they enter a cave (Myers 1960). These bats are migratory and exhibit an interesting seasonal distribution as a result. In summer, females move to the northern, eastern, and central United States to give birth and raise their young. Males, however, remain in the western states, generally in montane areas (Cryan 2003). This pattern of migration and sexual segregation is illustrated in Texas by the distribution of this species in the Chisos Mountains of Big Bend National Park. Here, hoary bats are a rare summer resident, and only males occur in the mountains at this time. In the spring and fall, however, both males and females are found (Easterla 1973; Higginbotham and Ammerman 2002). Interestingly, females are believed to precede males in migratory movements, which contrasts with the pattern found in migratory birds (Valdez and Cryan fall; males first appear in spring and remain throughout the summer in small numbers. Hoary bats are thought to prefer forested areas but also have been captured in lowland desert and along the Rio Grande in Texas. Although the overall pattern for this species in Texas is one of a spring-fall migrant, some hoary bats may also overwinter in the state. Museum specimen records suggest that some populations overwinter in coastal California or Mexico. Individuals have been observed in Arkansas, Indiana, and Pennsylvania in the winter (Doutt et al. 1966; Saugey et al. 1988; Whitaker 1967). Nonetheless, where the majority of individuals overwinter is largely unknown (Cryan 2003). Life History. The hoary bat typically roosts singly in deciduous or coniferous tree foliage, 3–19 m above the ground, and often near the edge of a clearing (Constantine 1966a; Gruver 2003; Perry and Thill 2007a). They prefer trees that are taller and larger than average in diameter and tend to roost in stands dominated by more mature trees (Jung et al. 1999; Perkins and Cross 1988; Perry and Thill 2007a). In Arkansas, hoary bats seem to preferentially roost on the east side of the canopies of pine and oak trees (Perry and Thill 2007a), whereas in Saskatchewan, Canada, they were found to roost on the southeastfacing branches of spruce trees (Willis and Brigham 2005). Roost sites also tend to have a relatively open flyway to facilitate the departure and arrival of these fast-flying bats, which have relatively low maneuverability compared to other forest species (Perkins and Cross 136 family vespertilionidae considerable distances from their diurnal roost sites (Black 1974). In South Carolina, they were more active above than below the forest canopy (Menzel et al. 2005). They have a strong preference for moths, which often constitute more than 90% of their diet (Black 1972, 1974; Carter et al. 2003a; Ross 1967; Valdez and Cryan 2009; Warner 1985). Indications are that the bat approaches a flying moth from the rear, engulfs the prey’s abdomen-thorax in its mouth, and then bites down, allowing the sheared head and wings to drop to the ground. Hoary bats preferentially feed on larger moths (wingspan of 8–31 mm) when compared to eastern red bats (Lasiurus borealis; Hickey et al. 1996; Shump and Shump 1982a). Hoary bats also are known to eat beetles, flies, true bugs, grasshoppers, termites, dragon- flies, and wasps (Ross 1967; Shump and Shump 1982a; Warner 1985; Zinn and Baker 1979). Although moths also dominate the diet of hoary bats in northern New Mexico during their spring migration , their eating habits shift to include more beetles later in the spring (Valdez and Cryan 2009). Female hoary bats change their foraging behavior based on their stage of reproduction. Foraging time increases by 73% between early lactation and fledging and then declines as the young become independent. Presumably this is to meet increased energy demands while raising young. Females with 2 pups forage for longer...