Foraging dispersion of Ryukyu flying-foxes and relationships with fig abundance in East-Asian subtropical island forests

Abstract

BackgroundFigs are widely distributed key resources to many tropical-subtropical animals, and flying-foxes are major consumers and seed dispersers of figs. Bat-fig interrelationships, however, may vary among species differing in fruiting traits, i.e., bat- versus bird-dispersed figs. We examined Ryukyu flying-fox foraging dispersion and the relationships with tree species composition and fig abundance in forests of Iriomote Island.ResultsBat foraging dispersion showed no spatial patterns with respect to different areas of the island, and was not explained by heterogeneity, density, or basal area (BA) of total trees, nor by relative density or BA of fruiting trees or total fruiting figs among sites. Instead, bat densities were positively dependent on the relative density of total figs, and particularly the relative BA of bat-dispersed figs Ficus septica and F. variegata. Both species were dominant figs in forests, fruiting asynchronously with long crop seasons, and were used as predominant foods. Bats foraged mostly solitarily and the mean density was in a hump-shaped relationship with crop sizes of the dominant bat-figs. These two species and Ficus benguetensis are larger-sized bat-figs, all contained more seeds, higher dry-pulp mass and water mass, but not necessarily water content. By approximate estimation, higher proportions of seeds of these bat-figs would have been removed from fruits through the bat consumption, than that of small-sized bird-figs like F. virgata, F. superba, and F. microcarpa.ConclusionsThe foraging dispersion of Ryukyu flying-foxes in forests depends on the availability of the most abundant bat-figs that serve as predominant foods. Intermediate levels of crop sizes of theses figs appear most fit with their solitary foraging. Our results suggest that as density and BA coverage of these dominant bat-figs are below a certain level, their effectiveness to attract bats may dwindle and so would their chance of dispersal by bats.

Seasonality of Pemba flying fox (Pteropus voeltzkowi) in selected habitats of Pemba Island, and its roles in seed dispersal and germination

“…The cover and space larger roosting trees provide ensure more protection and likely to aid the bats in avoiding disturbances. In general, the availability of feeding resources coupled with favourable resting roosts reduces flight distance and thus, increases the possibility of this species aggregating in a location (Kumar et al, 2018; Lee et al, 2017). Studies have provided evidence that areas with an abundance of preferred fruits and roosting trees are more likely to have large numbers of Old World fruit bats, particularly in the Pteropus genus (Granek, 2002).…”

Genetic diversity and population structure in the Ryukyu flying fox inferred from remote sampling in the Yaeyama archipelago

“…The Ryukyu flying fox (Pteropus dasymallus) is distributed across the Ryukyu archipelago in Japan, two small islands of Taiwan, and possibly in the Philippines [18,19]. P. dasymallus mainly eats fruits, nectar, and sometimes leaves, and plays an important role in pollination and seed dispersal [20][21][22][23]. P. dasymallus is listed as Vulnerable in the IUCN Red List [24] and has been the object of conservation concerns, due to rampant habitat degradation as well as to the recent discovery of previously unreported threat factors, such as predation by feral animals, powerline electrocutions, climatic stress (esp.…”

Comparing acoustic survey data for European bats: do walked transects or automated fixed-point surveys provide more robust data?

“…However, throughout Europe, walked transects with handheld detectors are more commonly used (Russo and Jones, 2003;Ciechanowski et al 2007;Stahlschmidt and Bruhl 2012;Henkens et al 2014;Goodenough et al 2015;Collins 2016). Outside of Europe, walked transects are used in Oceania (O'Donnell 2000;O'Donnell and Sedgeley, 2001;Scanlon and Petit 2009;Lavery et al 2020), Africa (Bambini et al 2006;Taylor et al 2013;Musila et al 2019), and Asia (Pottie et al 2005;Lee et al 2017;Mullin et al 2020). In addition to use in formal surveys for research, legislative complacence, and long-term monitoring, walked transects are increasingly being used in citizen science or volunteer-led bat surveys, for example in the Bat Walks Programme by Bat Conservation International and the National Bat Monitoring Programme in the UK.…”