HOME-RANGE SIZE AND SPACING PATTERNS OF MACROPHYLLUM MACROPHYLLUM (PHYLLOSTOMIDAE) FORAGING OVER WATER

Abstract

We studied home-range size and patterns of range use of long-legged bats, Macrophyllum macrophyllum (Phyllostomidae), at Barro Colorado Nature Monument, Panama, by using radiotelemetry. Movements of 4 males and 5 females fitted with radiotransmitters were monitored for 4–7 entire nights each between April and July 2002. M. macrophyllum had an extensive range compared to other similar-sized phyllostomid bats. Median home-range size for the 9 individuals tracked was 23.9 ha (range 7.3–150.7 ha). With a median of 17.3 ha (range = 7.3–24.9 ha), home ranges of males were somewhat, but not significantly, smaller than those of females (44.4 ha, range = 16.3–150.7 ha). The bats foraged exclusively over water, whereby hunting activity was restricted to the immediate shoreline of Gatun Lake. Foraging areas ranged from 2.7 to 96.1 ha, with a median of 12.3 ha for both sexes. In general, there was high night-to-night consistency in the use of foraging areas. Most bats had multiple foraging and core areas. Core-use areas corresponded to approximately 35% of the bats' foraging areas and were larger in females (median = 5.3 ha, range = 1.1–54.1 ha) than in males (3.3 ha, range = 2.6–8.7 ha). Maximum range span varied from 0.5 to 7.5 km, whereby males in general and 1 tracked harem male in particular foraged much closer to the day roost than did females. Individual M. macrophyllum traveled an estimated 35–47 km on a nightly basis, and females moved significantly greater distances than did males. Our results do not provide support for the proposition that small bats typically have small home ranges. In contrast, we conclude that foraging strategy, diet, dispersion of food resources, and wing morphology are generally better predictors of home-range size. Furthermore, reproductive condition, as well as intraspecific competition linked to colony size or social status, also strongly affect the spacing behavior and movement patterns of these bats. Our results suggest that, although M. macrophyllum employs a gleaning foraging strategy, it closely parallels aerial insectivorous bats in terms of range size and movement distances.