Anuran Diets Research Articles

Feeding ecology, reproductive biology, and sexual dimorphism of <i>Boana raniceps</i> (Anura: Hylidae) in an area of Caatinga, northeastern Brazil

The number of studies on the ecology of the genus Boana is vast in Brazilian biomes. Among the different species of this genus, B. raniceps is considered a common and widely distributed species. Despite this, only a few studies have explored the ecology of this species in the Caatinga biome. In this study we present information on the diet composition, reproduction, and sexual dimorphism of B. raniceps in the Caatinga biome, northeastern Brazil, providing additional information about the natural history of the species. We observed that B. raniceps has a generalist diet, consuming a great diversity of prey categories, but with a numerical and volumetric prevalence of Coleoptera. Interestingly, there was an ontogenetic and sexual variation in the diet, with the Relative Importance Index (RII) for each prey category differed between males, females, and juveniles. Females were found bearing mature eggs in both the rainy and dry seasons. The number of eggs carried by each female ranged from 153 to 3904. There was sexual dimorphism in body size, with females larger than males. However, size was not a limiting factor in fecundity. Here, we present new information on the natural history of B. raniceps and reinforce the need for further studies with widely distributed and known species. This is the first study to demonstrate ontogenetic and sexual variation in the diet of anurans of the genus Boana.

Non‐native stinging ant interactions with native anurans

AbstractNative predators may ignore or avoid non‐native prey because they do not recognize the novel organisms as food, or the invasive prey may bring antipredatory defences against which the native predators have not co‐evolved a sufficient attack. Non‐native ants successfully invade novel habitats worldwide and, in eastern North America, several invasive ant species bring venomous stings in quantities that far exceed that of native ant species. Ants make up a considerable portion of anuran diets, and we investigated how several native anurans reacted to the invasion of the non‐native European fire ant (Myrmica rubra). Myrmica rubra has a venomous sting, and it occurs in aggressive swarms that can deliver multiple stings. Despite these defences, based on field observations, we expected that leopard frogs (Lithobates pipiens) might consume the abundant ants. We also predicted that habitat niche differences from the moisture‐dependent ants would limit consumption by the more terrestrial American toads (Anaxyrus americanus) and more aquatic green frogs (Lithobates clamitans). Our results suggested that none of the anuran species make use of the M. rubra swarms. The anurans, particularly A. americanus, consumed ample native ants in the field, but not M. rubra ants. In the laboratory, A. americanus ate several M. rubra ants, and L. pipiens a few, but experienced anuran individuals collected from M. rubra‐invaded habitat were less likely to eat the ants in laboratory. Hence, at best, M. rubra invasion appears to supplant rather than supplement anuran food resources.

Rainy Season Food Availability for Anurans of Kimboza Forest Reserve, Tanzania

Amphibians are mostly considered to be generalist predators. Some species have a narrow diet or even specialize on certain prey categories. An assessment of the feeding habits of anuran species of Kimboza forest reserve, Tanzania was conducted during rainy season between March 2017 and June 2017. Through a visual encounter survey, 93 species were captured and analyzed for gut contents. About 462 prey items were identified the most abundant component being Isoptera and Hymenoptera. There was no significant difference (P > 0.05) in the anurans’ diet (composition or diversity or preferences) among different habitats of the forest (along boundaries and within the forest) but significant difference (P < 0.05) was found between the upper Stratum and the lower Stratum of the forest. The study provides a preliminary estimation of the actual diet of anurans and establishes a general feeding pattern for these species for the management of the Kimboza forest reserve. The study recommends the intensification of similar assessments in the nearby forest areas to come up with a complete description of the feeding habits for management purposes.

Feeding Ecology of a Tropical Litter-Dwelling Frog, Chaperina fusca (Microhylidae) from Borneo

We analyzed the diet of a litter-dwelling microhylid frog, Chaperina fusca, from the lowland rainforest of Borneo. We flushed the stomachs of 194 frogs: 94.8% had contents and 5.2% were empty. Although the diet composition of C. fusca was diverse, with 27 prey categories, we found that ants, mites, beetles, and springtails, in that order, dominated its diet both numerically and volumetrically. Among these four categories, however, ants were by far the most frequently consumed in both number (63.5%) and volume (82.6%) and in higher proportion than in the leaf litter. A novel aspect of our study, conducted in only a limited number of studies of anuran diets, was to determine the ant genera consumed. We identified 41 ant genera consumed by C. fusca whereby the genera Lophomyrmex, Pheidole, and Tetramorium were the most prominent. We also recorded a significant relationship of prey volume and number with both body size and mouth width of frogs. Our data provide circumstantial evidence that C. fusca is an ant-specialist feeder and active forager. These results are in line with the dietary characteristics of many terrestrial microhylid frogs in subtropical and tropical Asia, the Neotropics, and the Afrotropics.

Diet of bromeliad-frog Phyllodytes luteolus (Anura, Hylidae) in Atlantic Forest environments: what have the frogs been eating outside sandy coastal plains?

Knowledge about the diet of anurans in different environments is essential to understanding important aspects of their trophic ecology. The bromeliad-frog Phyllodytes luteolus inhabits tank bromeliads in sandy coastal plains and lowland forests on the mainland, as well as a continental island in southeastern Brazil. In this work, we describe and analyze the diet of P. luteolus in three environments. We obtained the consumed prey items of 92 frogs (32 from sandy coastal plain, 32 from lowland forest and 28 from the island) via a stomach-flushing procedure. We found some variations in consumed prey composition and prey volume across populations, but ants represented the most important consumed prey in all environments. Only ants had a relative importance greater than 50%, which may suggest a specialized diet that transcends the sandy coastal plain environment.

Diet evolution in litter frogs: reassessing the Toft’s hypotheses

Abstract In a series of papers starting in the early 1980s, Toft proposed a general scenario to explain dietary evolution in leaf litter anurans in which species would “form a continuum from those that specialize on ants and mites, through generalists, to species that avoid ants and mites”, and these differences would in turn correlate with foraging strategies, morphology, and defense mechanisms. In this study, we reassess this hypothesis using a global dataset on the dietary composition of 120 anuran species. Surprisingly, we found that the relative contribution of ants and mites in anuran diets were largely orthogonal to one another. Moreover, we did not find evidence for the continuum of dietary composition envisioned by Toft. These results suggest that, although ants and mites have played a major role in the evolution of aposematic species, the trends found in those species might not be directly extrapolated to all leaf litter anurans.

Trophic Discrimination Factors and Incorporation Rates of Carbon- and Nitrogen-Stable Isotopes in Adult Green Frogs, Lithobates clamitans.

Stable isotope analysis is an increasingly useful ecological tool, but its accuracy depends on quantifying the tissue-specific trophic discrimination factors (TDFs) and isotopic incorporation rates for focal taxa. Despite the technique's ubiquity, most laboratory experiments determining TDFs and incorporation rates have focused on birds, mammals, and fish; we know little about terrestrial ectotherms, and amphibians in particular are understudied. In this study we used two controlled feeding experiments to determine carbon (δ(13)C) and nitrogen (δ(15)N) isotope TDFs for skin, whole blood, and bone collagen and incorporation rates for skin and whole blood in adult green frogs, Lithobates clamitans. The mean (±SD) TDFs for δ(13)C were 0.1‰ (±0.4‰) for skin, 0.5‰ (±0.5‰) for whole blood, and 1.6‰ (0.6‰) for bone collagen. The mean (±SD) TDFs for δ(15)N were 2.3‰ (±0.5‰) for skin, 2.3‰ (±0.4‰) for whole blood, and 3.1‰ (±0.6‰) for bone collagen. A combination of different isotopic incorporation models was best supported by our data. Carbon in skin was the only tissue in which incorporation was best explained by two compartments, which had half-lives of 89 and 8 d. The half-life of carbon in whole blood was 69 d. Half-lives for nitrogen were 75 d for skin and 71 d for whole blood. Our results help fill a taxonomic gap in our knowledge of stable isotope dynamics and provide ecologists with a method to measure anuran diets.

Feeding in anuran communities on islands in the Danube floodplain

AbstractFeeding habits and food choice of anurans found on two islands in the lower Danube floodplain were studied for two years. The five most abundant anuran species included in this study were Bombina bombina, Hyla arborea, Pelobates fuscus, Rana esculenta and R. ridibunda. In B. bombina the niche breadths of young and adults were of similar magnitude and the degree of overlap between these size classes was high. In Rana esculenta complex young individuals had a much broader trophic niche than adults. A low degree of overlap existed between young and adults, suggesting that the various size classes exploit different segments of the prey resource. Overall, species with a larger size range consumed a higher prey diversity. Prey occurrence was sampled throughout the study on a regular basis. The analysis of selectivity in feeding using Ivlev's index showed that the prey taxa that appeared to be preferred were generally rare in the environment. Detrended Correspondence Analysis revealed that the composition of anuran diets were highly overlapping but differed from the composition of the resource base. The trophic resource was highly partitioned in space and time and thus allowed the coexistence of large populations with similar diets.

Diet Specialization in Small Vertebrates: Mite-Eating in Frogs

This study examines the morphological, taxonomic, ecological, and ontogenetic correlates of mite-eating (acariphagy) in anurans to increase our understanding of diet specialization in vertebrate insectivores . In a review of the literature (Part I), mites were abundant in terrestrial habitats at many locations worldwide, yet mites are not commonly reported as prey in anuran diets. In a detailed study of tropical ground-dwelling anurans (Part II), the diets of all species included mites