The nocturnal distribution and resource use by Ryukyu flying foxes was studied along 28 transects, covering five types of habitats, on Iriomote Island, Japan, from early June to late September, 2005. Bats were mostly encountered solitarily (66.8%) or in pairs (16.8%), with a mean linear density of 2.5 ± 0.6 bats/km of transect/night. Across the island, however, bat densities were distributed non-randomly among transect-nights, not correlated with transect length, and showed a slightly clumped distribution (variance/mean = 3.3). Outskirt trails contributed higher values to the relative importance of bat abundance, but the highest mean abundances occurred mostly at village sites on the west coast, which on average devoted only a quarter of their land area to agriculture/husbandry compared to those on the east coast. This supports our prediction that higher bat abundances are found in areas with less anthropogenic interference and more forest. Among habitats, the mean total abundance and density were lower in cultivated areas than in villages and inland forests. Bat perches in cultivated areas were also lower, and were in correspondence with lower shrub and canopy heights, and less canopy coverage. Flying fox abundance was correlated moderately with the heterogeneity of the tree composition, and strongly with the density of major fruiting trees. Thirty-nine species of plants and some animal items were used by Ryukyu flying foxes, including at least 31 species of fruits, 13 species of flowers, and leaves of seven species, with 14 species new to the record. Ficus septica and F. variegata were the most frequently encountered and dominant items in both fecal and rejecta/dropped samples, followed mostly by other figs and mulberries in the former, but by larger-seed non- Moraceae plants in dropped samples. Our results suggest that for conservation of flying foxes undisturbed forests providing an adequate resource basis are of major importance.
Bats of the family Rhinolophidae emit their echolocation calls through their nostrils and feature elaborate noseleaves shaping the directionality of the emissions. The calls of these bats consist of a long constant-frequency component preceded and/or followed by short frequency-modulated sweeps. While Rhinolophidae are known for their physiological specializations for processing the constant frequency part of the calls, previous evidence suggests that the noseleaves of these animals are tuned to the frequencies in the frequency modulated components of the calls. In this paper, we seek further support for this hypothesis by simulating the emission beam pattern of the bat Rhinolophus formosae. Filling the furrows of lancet and removing the basal lappets (i.e., two flaps on the noseleaf) we find that these conspicuous features of the noseleaf focus the emitted energy mostly for frequencies in the frequency-modulated components. Based on the assumption that this component of the call is used by the bats for ranging, we develop a qualitative model to assess the increase in performance due to the furrows and/or the lappets. The model confirms that both structures decrease the ambiguity in selecting relevant targets for ranging. The lappets and the furrows shape the emission beam for different spatial regions and frequency ranges. Therefore, we conclude that the presented evidence is in line with the hypothesis that different parts of the noseleaves of Rhinolophidae are tuned to different frequency ranges with at least some of the most conspicuous ones being tuned to the frequency modulated components of the calls—thus yielding strong evidence for the sensory importance of the component.
Flycatching is relatively uncommon in insectivorous bats, yet members of the family Rhinolophidae constitute over one-half of the documented flycatching species. The Formosan woolly horseshoe bat, Rhinolophus formosae, is among the largest in size and relies primarily on flycatching for foraging. We assessed perch use of flycatching R. formosae in relation to vegetation structure in tropical monsoon forests in southern Taiwan. We located bats using acoustic detectors in forest interior and edge-open forest sites, and measured perch features, dispersion of the nearest trees, and vegetation structure within a 5-m radius of each perch. The same measurements were applied to randomly selected perches in both habitats where bats were not detected. We found no seasonal effects or differences between used and random perches in perch features, dispersion of neighboring trees, or vegetation structure surrounding the perches. Perches used at edge-open forest sites were farther from the perch tree trunk and neighboring trees, and surrounded by larger trees than in forest interiors. In contrast, perches in forest interiors were surrounded by higher shrub and reef layers and greater canopy, shrub, and reef layer cover, than those at edge-open forests. Overall, perches in forest interiors were in more cluttered settings, containing higher vegetation obstacles than edge-open habitats. In both habitats, vegetation obstacles generally increased in a curvilinear manner when moving horizontally and downward from the perch. However, in forest interiors perches used by bats had significantly lower vegetation obstacles horizontally and downwardly and were less cluttered than randomly selected perches. Overall, our results indicate that R. formosae in forest interiors selectively used perches associated with more open space that allows for more maneuverable sally flights and a longer detection range suitable for its exceptionally low constant frequency calls to explore less cluttered environments.
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