Food habits of two species of tube-nosed bats, Murina hilgendorfi and Murina ussuriensis, in Hayakawa, central Japan

Knowledge of food habits is essential for understanding the life history of a species; however, such information about the enigmatic Murina genus of bats is little known. In this study, we examined the food habits of Murina hilgendorfi and Murina ussuriensis over four years in Hayakawa, central Japan, using traditional morphological fecal analysis. Fragments of arthropods of six orders (five identified families), and of five orders (five identified families), were found in the feces of M. hilgendorfi and M. ussuriensis, respectively. Both species consumed wingless arthropods (caterpillars and spiders), insects that rarely fly (ground beetles and bush crickets), or diurnal insects (dragonflies and hoverflies; i.e., that are resting at night) during the night, which is a clear indication of gleaning behavior in these bats. In spring, the large-bodied M. hilgendorfi more frequently consumed hard-bodied insects such as beetles and bush crickets, whereas the small-bodied M. ussuriensis more frequently consumed soft-bodied insects such as caterpillars, moths, spiders, and dipterans, suggesting that the body size difference influences their food habits, which may have contributed to food resource partitioning between these closely related bats. For M. hilgendorfi, beetles were the main prey in spring and autumn, while caterpillars and grasshoppers were more frequently consumed in spring and autumn, respectively, suggesting that they may have changed prey items according to seasonal fluctuations in food availability. To our knowledge, this study provides the first record of differences in the food habits of these two species.

Comparative isotope ecology of western Amazonian rainforest mammals

Closed-canopy rainforests are important for climate (influencing atmospheric circulation, albedo, carbon storage, etc.) and ecology (harboring the highest biodiversity of continental regions). Of all rainforests, Amazonia is the world’s most diverse, including the highest mammalian species richness. However, little is known about niche structure, ecological roles, and food resource partitioning of Amazonian mammalian communities over time. Through analyses of δ13Cbioapatite, δ13Chair, and δ15Nhair, we isotopically characterized aspects of feeding ecology in a modern western Amazonian mammalian community in Peru, serving as a baseline for understanding the evolution of Neotropical rainforest ecosystems. By comparing these results with data from equatorial Africa, we evaluated the potential influences of distinct phylogenetic and biogeographic histories on the isotopic niches occupied by mammals in analogous tropical ecosystems. Our results indicate that, despite their geographical and taxonomic differences, median δ13Cdietvalues from closed-canopy rainforests in Amazonia (−27.4‰) and equatorial Africa (−26.9‰) are not significantly different, and that the median δ13Cdietexpected for mammalian herbivores in any closed-canopy rainforest is −27.2‰. Amazonian mammals seem to exploit a narrower spectrum of dietary resources than equatorial African mammals, however, as depicted by the absence of highly negative δ13Cdietvalues previously proposed as indicative of rainforests (<−31‰). Finally, results of keratin and bioapatite δ13C indicate that the predictive power of trophic relationships, and traditional dietary ecological classifications in bioapatite-protein isotopic offset expectations, must be reconsidered.

Food resource partitioning among species of Astyanax (Characiformes: Characidae) in the Lower Iguaçu River and tributaries, Brazil

ABSTRACT Resource partitioning allows for interspecific coexistence and is frequently reported for similar species. Here, we predicted the existence of resource partitioning among species of Astyanax that co-occur in the Low Iguaçu River and tributaries in Brazil. A total of 848 stomachs of five species of Astyanax were analyzed. Algae, terrestrial plant and fruit/seed were the most consumed resources. Astyanax bifasciatus and A. dissimilis had predominantly herbivorous diets, A. gymnodontus and A. lacustris were omnivorous, and A. minor was mainly algivorous. Permutational analysis of variance showed the species had different diets, and similarity percentage analysis indicated that fruit/seed and terrestrial plant contributed the most to this differentiation. A paired comparison indicated that the trophic breadth of A. gymnodontus differed from that of other species. The food overlap was low for 55% of Astyanax pairs. These results showed alignment with the niche theory, in which differentiation in the use of food resources facilitates the coexistence of species and minimizes competition. These adjustments to coexistence become relevant in the context of endemic species in a highly isolated basin under intense threat (dams, species introduction, deforestation, and pollution) as is the case for the Iguaçu River basin.

Intraspecific food resource partitioning in Brazilian silverside Atherinella brasiliensis (Atheriniformes: Atherinopsidae) in a tropical estuary, Brazil

ABSTRACT We investigated the intraspecific partitioning of food resources of the Brazilian silverside Atherinella brasiliensis in a tropical estuary. A total of 1,099 stomachs were analyzed, and the diet consisted mainly of Gastropoda, Ceratopogonidae larvae, Decapoda larvae, Calanoida, Cyclopoida, Hymenoptera and Brachyura. Ordination of the mean volumetric percentage contribution of preys indicated differences in the dietary compositions between sites and size classes. By SIMPER analysis, we detected high dissimilarity between size classes, suggesting ontogenetic niche shifts: the diet of the early juveniles was based in zooplankton, whereas adults consumed mainly benthic macroinvertebrates. These shifts were related to changes in feeding structures and foraging abilities that show a strong relationship with body size, and showed functional trade-offs in swimming capacity, and feeding strategies used to capture prey. Differences in the diet between size classes and habitat selection by Brazilian silverside are likely strategies to avoid intraspecific competition, clearly related to the abundance and accessibility of resources along the estuarine habitats.