Perch use by flycatching Rhinolophus formosae in relation to vegetation structure

Abstract

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.

Comparative echolocation and foraging ecology of horseshoe bats (Rhinolophidae) and Old World leaf-nosed bats (Hipposideridae)

“…Cluttered areas are not necessarily restricted to stands of continuous vegetation, with some Rhinolophus species exploiting edge habitat such as hedgerows, edges of stands of forest and internal forest edges (e.g. Bontadina et al 2002;Law and Chidel 2002;Russo et al 2002Russo et al , 2005Goiti et al 2008;Jiang et al 2008;Lee et al 2012Lee et al , 2020Law et al 2020).…”

Perch time allocation and feeding efficiency of flycatching Rhinolophus formosae: an optimal foraging behavior?

“…Perch hunting bats are typified by broad wingtips and lower aspect ratios that allow for maneuverable flight in more cluttered space with dense vegetation [ 15 ]. While some of them are narrow-space gleaning foragers [ 14 ], nearly two third of perch hunting species use a true flycatcher style, although mostly retain the use of aerial hunting by continuous flight [ 16 ], and some are capable of gleaning (e.g., Rhinolophus blasii [ 17 ]). Among those species which do adopt flycatching, horseshoe bats ( Rhinolophus spp., Rhinolophidae) account for a predominant proportion.…”

“…Among those species which do adopt flycatching, horseshoe bats ( Rhinolophus spp., Rhinolophidae) account for a predominant proportion. Their foraging has stronger associations with finer habitat features and vegetation structure, so is potentially more susceptible to habitat alteration and disturbance [ 16 ].…”

“…Perch hunting resembles a sit-and-wait foraging mode and is less mobile than aerial hawking, thus it is particularly intriguing to consider the effect of foragers’ selectivity on the time spent at a feeding perch and the timing of the decision to move to a new perch (i.e., the giving-up time [ 27 , 28 ]). Yet, the foraging behavior of most flycatching horseshoe bats, particularly in field conditions, has attracted relatively little attention thus far [ 16 ].…”

“…It is an endemic species to Taiwan and one of the most restrictedly distributed among all rhinolophids [ 29 ]. Among all known flycatching horseshoe bats, R. formosae is one of the largest, but emits echolocation calls of the lowest frequency for its size [ 16 ] (except R. paradoxolophus [ 14 ]). Notably, it prefers edges and open forests to forest interiors [ 16 ], where forest edges and open forests generally represent background cluttered spaces, and forest interiors correspond to highly cluttered spaces [ 30 ].…”