Resource utilization and guild structure of small vertebrates in the Amazon forest leaf litter

The Batrachian Barf Bowl: An authentic research experience using ecological data from frog diets

Authentic research experiences (AREs) are a powerful strategy for inspiring and retaining students in science, technology, engineering, and math (STEM) fields. However, recent demand for virtual learning has emphasized the need for remote AREs that also foster a sense of community and interpersonal connections among participants. Here, we describe an ARE activity that leverages digitized diet data from natural history collections to provide students with collaborative research experience across any learning environment. Using magnified photographs of frog stomach contents collected in the Peruvian Amazon, we designed an open‐source “bowl game” competition that challenges students to identify, measure, and compare diet items across vouchered frog specimens (“Batrachian Barf Bowl”). To demonstrate learning outcomes, we ran this activity with 39 herpetology class students from the University of Notre Dame and the University of Michigan. We used pre‐ and post‐activity assessments to evaluate effectiveness, scientific accuracy of results, and impact on student well‐being. With minimal preparation and training in invertebrate identification, students were successful in identifying hundreds of frog diet items to taxonomic order, although accuracy varied among clades (global accuracy ~70%). While we found no difference in science identity, community, or self‐efficacy between the two institutions at either time point (pre‐ and post‐activity), we found that well‐being was significantly higher for both sets of students after the activity. Overall, this approach offers a model for combining active learning with museum collections to provide experiential research opportunities that highlight the power of scientific collaboration.

Ontogenetic variation in the diet of the anuran community from a semi-arid environment in the southeastern Chihuahuan Desert

Although ontogeny influences dietary composition and trophic niche breadth in many anurans, its effects on diet have been little analyzed in sympatric species. In this study, we analyzed interspecific and ontogenetic variation in dietary composition and trophic niche width in an anuran community from a semi-arid environment. We found a more profound effect of species identity than body size on dietary composition, with the diet of four species dominated by formicids, that of two others by coleopterans and formicids, and that of the remaining species not dominated by specific prey types. We found ontogenetic changes in dietary composition in three of four species analyzed, in which consumption of some small insects decreased as predator size increased, regardless of species. Additionally, we did not find ontogenetic change in prey number consumed in any of the four species, but prey size increased with increasing predator size in all of them. Most species exhibited a narrow trophic niche, which was even narrower in adults in three of the four species analyzed. Costello's modified plots revealed a high variation among individuals in termite consumption in Anaxyrus punctatus, and in more prey types in Spea multiplicata. Our results suggest that this community is not size-structured, and that ontogenetic diet shifts are mainly caused by passive sampling toward prey of different sizes. Finally, comparisons with previous data revealed an interpopulation pattern, in which trophic niche width contracts as aridity increases, possibly because of an increase in interspecific competition for trophic resources.

Dietary relationships among coexisting anuran amphibians: a worldwide quantitative review

Anuran amphibians have traditionally been considered suitable model organisms for community ecology studies. In this paper, we review and quantitatively re-analyze the original studies published on dietary relationships among anuran communities worldwide. We re-analyzed 33 independent communities from all continents, including data on prey numbers and/or prey volumes. All datasets underwent null model re-analysis using two randomization algorithms. In addition, logistic regression models were used to identify specific assemblage patterns. We discovered three main patterns: (1) one particular algorithm (RA2, which replaces every cell in the matrix with one randomly chosen, but retains the zero structure of the matrix) performed much better at uncovering community structure; (2) nonrandom structure was more likely to occur in tropical than in nontropical regions; (3) prey volume was a better descriptor of dietary relationships than prey number when attempting to detect nonrandom structure. We showed that: pattern (1) depended on both the overall generalist nature of the anurans in general and on the mathematical properties of RA2; pattern (2) was consistent with theoretical attributes of tropicality; and pattern (3) was due to the intrinsic ecological properties of generalist organisms, which forage more or less opportunistically on prey of very different sizes; hence, when prey number is used as a diet descriptor, there is a risk of approximating different prey taxa that make different relative volume contributions to the overall diet as being of similar relevance .

Parameters from the community of leaf-litter frogs from Estação Ecológica Estadual Paraíso, Guapimirim, Rio de Janeiro State, southeastern Brazil

We studied the leaf-litter frog community of Estação Ecológica Estadual Paraíso, in Guapimirim, Rio de Janeiro State, southeastern Brazil. Herein we combined three sampling methods (large plots, visual encounter surveys and pit-fall traps) to present data on species composition, richness, relative abundance and densities. The local assemblage of frogs associated to the leaf-litter was composed by 14 species, belonging to nine families. Haddadus binotatus, a direct-developing frog, was the most abundant species in the community. The estimated density of the local leaf-litter frog assemblage based on plot sampling was 4.3 frogs/100 m². Haddadus binotatus had the highest density (1.1 ind/100 m²). Frogs were predominantly found at night. Thoropa miliaris had the largest values of SVL (39.0 ± 10.3 mm), whereas the smallest species were Euparkerella brasiliensis (16.7 ± 2.2 mm) and E. cochranae (16.0 ± 2.7 mm). Rhinella ornata had the highest mean body mass (12.1 ± 7.5 g), and E. cochranae the lowest (0.4 ± 0.2 g). The overall frog mass was 938.6 g/ha. Our data support that higher densities of leaf-litter frogs tend to occur in the Neotropical region compared to the OldWorld tropics, tending to be higher in Central America than in South America.

Impacto do desmatamento e formação de pastagens sobre a anurofauna de serapilheira em Rondônia

A riqueza e a diversidade de anfíbios anuros de serapilheira em áreas de floresta e de pastagem foram estudadas em Rondônia. A eficiência da utilização de armadilhas de interceptação e queda foi analisada. As armadilhas foram instaladas em três ambientes distintos: interior de floresta, distante de ambientes aquáticos permanentes; interior de floresta, a cerca de 100 metros de rio; área de pastagem, distante de ambientes aquáticos permanentes. Foram capturados 1.324 espécimes pertencentes a 27 espécies, distribuídas em nove famílias: Aromobatidae (1 espécie), Brachycephalidae (2), Bufonidae (4), Cycloramphidae (1), Dendrobatidae (1), Hylidae (5), Leiuperidae (1), Leptodactylidae (7) e Microhylidae (5). O emprego de armadilhas de interceptação e queda permitiu registrar 57% das espécies conhecidas para essa localidade, sendo particularmente eficiente para a captura de anuros de hábitos terrícolas e fossoriais. Foram capturados menos indivíduos nos três meses mais secos e houve maior diversidade durante a estação chuvosa. Maior riqueza e diversidade foram registradas nos ambientes florestados, em relação à pastagem, observando-se decréscimo de espécies com o desmatamento. A conversão da floresta em pastagens ocasiona modificações no ambiente (diminuição de locais para reprodução, diminuição da disponibilidade de alimento, perda da serapilheira, compactação do solo, alterações microclimáticas, aumento da abundância de espécies de áreas abertas, etc.) criando condições desfavoráveis para a sobrevivência de algumas espécies.

Gluttonous predators: how to estimate prey size when there are too many prey

Prey size is an important factor in food consumption. In studies of feeding ecology, prey items are usually measured individually using calipers or ocular micrometers. Among amphibians and reptiles, there are species that feed on large numbers of small prey items (e.g. ants, termites). This high intake makes it difficult to estimate prey size consumed by these animals. We addressed this problem by developing and evaluating a procedure for subsampling the stomach contents of such predators in order to estimate prey size. Specifically, we developed a protocol based on a bootstrap procedure to obtain a subsample with a precision error of at the most 5%, with a confidence level of at least 95%. This guideline should reduce the sampling effort and facilitate future studies on the feeding habits of amphibians and reptiles, and also provide a means of obtaining precise estimates of prey size.

Adapting to the unpredictable: reproductive biology of vertebrates in the Australian wet-dry tropics

In the wet-dry tropics of northern Australia, temperatures are high and stable year-round but monsoonal rainfall is highly seasonal and variable both annually and spatially. Many features of reproduction in vertebrates of this region may be adaptations to dealing with this unpredictable variation in precipitation, notably by (i) using direct proximate (rainfall-affected) cues to synchronize the timing and extent of breeding with rainfall events, (ii) placing the eggs or offspring in conditions where they will be buffered from rainfall extremes, and (iii) evolving developmental plasticity, such that the timing and trajectory of embryonic differentiation flexibly respond to local conditions. For example, organisms as diverse as snakes (Liasis fuscus, Acrochordus arafurae), crocodiles (Crocodylus porosus), birds (Anseranas semipalmata) and wallabies (Macropus agilis) show extreme annual variation in reproductive rates, linked to stochastic variation in wet season rainfall. The seasonal timing of initiation and cessation of breeding in snakes (Tropidonophis mairii) and rats (Rattus colletti) also varies among years, depending upon precipitation. An alternative adaptive route is to buffer the effects of rainfall variability on offspring by parental care (including viviparity) or by judicious selection of nest sites in oviparous taxa without parental care. A third type of adaptive response involves flexible embryonic responses (including embryonic diapause, facultative hatching and temperature-dependent sex determination) to incubation conditions, as seen in squamates, crocodilians and turtles. Such flexibility fine-tunes developmental rates and trajectories to conditions--especially, rainfall patterns--that are not predictable at the time of oviposition.

Ambientes e temporada de vocalização da anurofauna no Município de Espigão do Oeste, Rondônia, Sudoeste da Amazônia: Brasil (Amphibia: Anura)

Um levantamento da anurofauna foi realizado na Fazenda Jaburi (11° 35’-11° 38’ S e 60° 41-60° 45’ W), Município de Espigão do Oeste, Estado de Rondônia, Brasil, analisando a distribuição espacial e período da atividade de vocalização das espécies registradas em áreas de floresta primária e de pastagem. O trabalho de campo na Fazenda Jaburi foi realizado entre fevereiro de 2001 e março de 2002. Para amostragem das espécies, diferentes ambientes foram investigados intensivamente por procura ativa e também por armadilhas de interceptação e queda. Um total de 47 espécies, pertencentes a dez famílias foi registrado: Aromobatidae (1), Brachycephalidae (2), Bufonidae (4), Centrolenidae (1), Cycloramphidae (1), Dendrobatidae (1), Hylidae (23), Leiuperidae (1), Leptodactylidae (8) e Microhylidae (5). Novos registros para o Estado de Rondônia são as seguintes espécies: Dendropsophus acreanus, Trachycephalus resinifictrix, Chiasmocleis bassleri e C. ventrimaculata. A maioria das espécies apresentou atividade de vocalização durante o período chuvoso (outubro a março), e houve correlação significativa entre a atividade de vocalização e a pluviosidade. Foi encontrada a maior riqueza de espécies nas áreas de floresta do que nas de pastagem, podendo ser um indicativo de que o desmatamento pode provocar a diminuição da riqueza de espécies.

Evidence of terrestrial feeding in the arboreal lizard Enyalius bilineatus (Sauria, Polychrotidae) of south-eastern Brazil

The diet of the arboreal lizard E. bilineatus was assessed based on analysis of gut contents of specimens collected in the remnants of the Atlantic rainforest in Espírito Santo State, south-eastern Brazil. Stomachs of the lizards examined (SVL = 57.0-85.0 mm) contained nine arthropod orders. E. bilineatus utilizes a broad range of arthopodan prey type and sizes, and can be considered an arthropod generalist, which uses a sit-and-wait foraging strategy. Orthoptera represented the most important food item, followed by Dictyoptera and Hymenoptera. Hemiptera, Homoptera, Lepidoptera (larvae), Coleoptera, Araneae, and Diplopoda constituted the remainder of food items. The presence of Diplopoda, which are not generally found on tree trunks, provides particularly strong evidence the E. bilineatus forages in leaf litter on the ground.

Resource use of five sympatric turtle species: effects of competition, phylogeny, and morphology

I quantified resource use with respect to habitat, diet, and diel and seasonal use of basking time for five sympatric turtle species in a cove on Kentucky Lake, an impoundment of the lower Tennessee River in western Kentucky, U.S.A. I used pseudocommunity analyses to test for significant structure in resource use, compared resource-use matrices with matrices representing phylogenetic similarity, and measured morphological characteristics related to resource use. Three strictly riverine species (Graptemys pseudogeographica, Graptemys ouachitensis, and Apalone mutica) with relatively long limbs and digits used outer portions of the cove near deeper waters to a greater extent than did two shorter-limbed species (Trachemys scripta and Pseudemys concinna), which inhabit both lotic and lentic waters. Only the difference in habitat between A. mutica and the other four species was shown to be significant in pseudocommunity analysis, a result that can be better explained by differences in basking substrates than by competition. Dietary studies indicated two guilds, omnivore and algivore, in spite of the low pairwise overlap values that resulted from overall prey diversity. Analysis of use of diel and seasonal basking time revealed significant structure (partitioning) at only the rank of second-nearest neighbor for seasonal time. Clustering phenograms for resource similarity among the five species were overall highly similar to two phylogenetic hypotheses. Phylogeny was thus shown to be of greater importance in structuring resource use in Kentucky Lake than interspecific competition. In addition, the similarity in clustering phenograms was not consistent with the hypothesis of niche complementarity, suggesting that interspecific competition was of little importance.

Organization of a taxonomically diverse lizard assemblage in Amazonian Ecuador

Of 22 lizard species studied in eastern Ecuador, 21 were diurnal. Ten were active foragers and 12 were sit-and-wait foragers. Considerable variation existed in habitat and microhabitat distribution and body temperatures among species. Body size varied over an order of magnitude (20–270 mm snout–vent length). Most morphological (size-free) variation among species (77%) was accounted for by two principal component axes and appears tied to phylogeny. Prey size was correlated with lizard size and species were separated by prey size. Low overlaps in microhabitat, habitat, and prey type also separated species. Pseudocommunity analysis indicated structure in the consumer–resource matrix. In some comparisons, prey overlaps among species were greater within than between higher taxa, and closely related species tended to be found in similar habitat patches and microhabitats, suggesting that resource-use patterns are determined to some extent by phylogeny. Ecology, morphology, and phylogeny appear tied together in a complex manner, with resource partitioning contributing to maintenance of structure. Historical interactions among closely related species may have been important in determining which species within particular clades invaded and persisted within local assemblages in lowland forest.