Diet and resource partitioning among anurans in irrigated rice fields in Pantanal, Brazil

Abstract

Artificial ponds or irrigated systems scattered throughout farmlands can offer important habitats for anurans and can be interesting sites for research on species resources use in a changing landscape. This study describes the diet and resource partitioning among anurans inhabiting irrigated rice fields in the Pantanal region. Twenty categories of prey were found in the stomachs of Leptodactylus chaquensis, L. elenae, L. podicipinus and Rhinella bergi, the most frequent being Coleoptera, Hymenoptera, larvae of Hexapoda, Hemiptera, Diptera and Orthoptera. The great differences found in the diet of these species in rice fields compared to other locations, according to available records in the literature, was the increased importance of Hemipitera and Orthoptera and the decrease in importance of Hymenoptera in the diet of leptodactylids. These differences might be attributed to changes in the availability of resources in response to habitat modification. Although diet composition was very similar among species, niche overlap was larger than expected by chance, suggesting that the competition for food resources is not, or has not been, a significant force in determining the structure of this frog community. Two non-exclusive hypotheses could be considered as a justification for this result: 1) the high niche overlap could result from resource availability, which is sufficient to satisfy all species without any strong competition; 2) or the high values of niche overlap could be a selective force driving species to compete, but there has not been enough time to express a significant divergence in the species diet because the study area is characterised as a dynamic habitat influenced by frequent and cyclical changes.Keywords: niche overlap, agroecosystems, Leptodactylidae, Bufonidae, diet. Dieta e partição de recursos entre anuros em campos de rizicultura no Pantanal, Brasil ResumoLagoas artificiais e sistemas irrigados em áreas de produção agrícola podem oferecer habitats importantes a anuros e ser significativos para investigações sobre o uso de recursos pelas espécies em ambientes modificados. Este estudo descreve a dieta e partição de recursos tróficos entre anuros de campos de rizicultura na região do Pantanal. Nos estômagos de Leptodactylus chaquensis, L. elenae, L. podicipinus e Rhinella bergi foram encontradas 20 categorias de presas, sendo Coleoptera, Hymenoptera, larvas de Hexápoda, Hemiptera, Diptera e Orthoptera as mais frequentes. Maiores diferenças encontradas na dieta dessas espécies em campos de arroz comparadas a de outros locais, de acordo com dados da literatura, foram o aumento da importância de Hemipitera e Orthoptera e a diminuição na importância de Hymenopteras na dieta dos leptodactilídeos. Essas diferenças talvez sejam reflexos de mudanças na disponibilidade de recursos de presas, em resposta às modificações ambientais. Apesar de as espécies apresentarem dietas bastante similares, a sobreposição de nicho foi maior que a esperada ao acaso, sugerindo que a competição por recursos aliment...

Frogs as potential biological control agents in the rice fields of Chitwan, Nepal

“…These results are consistent with the few previous dietary studies of anurans in rice fields (Hirai and Matsui, 2000;Piatti and Souza, 2011). Previous studies also show that ants (hymenopterans) are one of the most common prey for most anuran frogs (Hirai, 2004;Kidera et al, 2008;Sabagh and Carvalho-e-Silva, 2008).…”

“…Despite the large number of studies describing dietary habits of anurans (e.g. Hirai andMatsui, 1999, 2002;Santos et al, 2004;Sabagh and Carvalho-e-Silva, 2008;Quiroga et al, 2009;Piatti and Souza, 2011), there is a paucity of studies about frog diets in rice fields (Hirai and Matsui, 2002;Piatti and Souza, 2011;Yousaf et al, 2010) and virtually no information is available from Nepal (but see Khatiwada et al in review). Some of the most important anuran dietary groups include coleoptera, lepidoptera, orthoptera, homoptera, hemiptera (Hirai and Matsui, 1999;Mahan and Johnson, 2007).…”

Habitat heterogeneity and anuran community of an agroecosystem in the Pantanal of Brazil

“…Land management, along with natural flooding, increase availability of humid habitat in the area. The Rio Miranda is the main source of water from which artificial flooding occurs through systems of drainage channels (Piatti et al 2010, Piatti andSouza 2011). Thus, water is not a limiting resource in this agroecosystem.…”

“…However, some species seem adapted to living in the marginal transitional zones between agro-and natural ecosystems (Altieri 1999). Several studies of the effects of agroecosystems on biodiversity have appeared in the last decade (Zamora et al 2007, Duré et al 2008, Piatti et al 2010, Piatti and Souza 2011. It has become clear that it is important to distinguish the impacts of agricultural practices as opposed to natural processes on habitats over limited temporal and spatial scales (Benton et al 2003, Hill and Hamer 2004, Jepsen et al 2005.…”

“…Wetlands throughout the world, including the Pantanal, are diminishing owing to agriculture. Natural wetlands are being functionally replaced by irrigated fields, which harbor many aquatic species, including amphibians (Duré et al 2008, Machado and Maltchik 2010, Piatti et al 2010, Piatti and Souza 2011; however, drainage activities and land management of these aquatic systems are thought to be harmful to anurans (Colombo et al 2008). Thus, any information about the relationship between anuran populations and habitat complexity is strategically important to sound environmental management practice, especially in regions with high deforestation activities.…”