Diet of Ameerega Braccata

Diet of Ameerega braccata (Steindachner, 1864) (Anura: Dendrobatidae) from Chapada dos Guimarães and Cuiabá, Mato Grosso State, Brazil Forti, LR.a,d*, Tissiani, ASO.a, Mott, T.a,b and Strüssmann, C.a,c aPrograma de Pós-graduação em Ecologia e Conservação da Biodiversidade, Instituto de Biociências, Universidade Federal de Mato Grosso – UFMT, Av. Fernando Corrêa da Costa, 2367, Bairro Boa Esperança, CEP 78060-900, CCBS-II, Boa Esperança, Cuiabá, Mato Grosso, Brazil bDepartamento de Biologia e Zoologia, Universidade Federal de Mato Grosso – UFMT, Av. Fernando Corrêa da Costa, 2367, Bairro Boa Esperança, CEP 78060-900, Cuiabá, Mato Grosso, Brazil cDepartamento de Ciências Básicas e Produção Animal, Faculdade de Agronomia e Medicina Veterinária e Zootecnia, Universidade Federal de Mato Grosso – UFMT, Av. Fernando Corrêa da Costa, 2367, Bairro Boa Esperança, CEP 78060-900, Cuiabá, Mato Grosso, Brazil dPrograma Interunidades de Pós-graduação em Ecologia Aplicada, Escola Superior de Agricultura “Luiz de Queiroz”, Universidade de São Paulo – USP, Av. Pádua Dias, 11, CP 9, CEP 13418-900, Piracicaba, SP, Brazil *e-mail: [email protected] Received December 2, 2009 – Accepted February 4, 2010 – Distributed February 28, 2011 (With 3 figures) Abstract The understanding of feeding habits is important for anurans in general, both from an ecological and a phylogenetic perspective. For diurnal poison frogs belonging to the Dendrobatidae family, diet aspects play a crucial role in their defense and survival. Herein, we investigated feeding habits, foraging behaviour, and overall effects of habitat, sex, and body size on the diet of individuals of Ameerega braccata, a poorly known dendrobatid species. Specimens were observed and collected in the type-locality, Chapada dos Guimarães, and in the neighbouring municipality of Cuiabá, both in the State of Mato Grosso, Midwestern Brazil. The most important prey categories for A. braccata were Formicidae, Isoptera, and Acari, whose representatives were caught during active foraging. Individuals from Chapada dos Guimarães population consumed more Acari but fewer Isoptera than individuals from Cuiabá. Despite this, niche breadth values were narrow and similar for the two populations. Individuals from two distinct habitats (campo sujo and cerrado stricto sensu) showed differences in their diet, probably as an effect of differential prey availability. Females consumed more Isoptera than males. The number of prey categories used as food was not influenced by the variation of body size of the target species. However, the abundance and the volume of consumed Acari were statistically correlated with body size. The main results suggest that Ameerega braccata has a narrow niche breadth, as well as a specialised diet in ants, termites, and mites, which reinforces the hypotheses of close association between Acari consumption and the presence of skin toxic alkaloids, already found in other species of Dendrobatidae. Although differences in prey consumption between sexes are uncommon among poisonous frogs, differences in the diet composition between age classes, which probably reduce intraspecific competition, are frequently reported. Keywords: Ameerega braccata, niche breadth, Anura, Dendrobatidae, diet. Dieta de Ameerega braccata (Steindachner, 1864) (Anura: Dendrobatidae) de Chapada dos Guimarães e Cuiabá, Estado do Mato Grosso, Brasil Resumo A compreensão de hábitos alimentares é de relevância ecológica e filogenética para espécies de anuros em geral. Para sapos diurnos da família Dendrobatidae, aspectos da dieta exercem papel crucial na defesa e, consequentemente, na sobrevivência. No presente trabalho, investigamos a composição alimentar, comportamento de obtenção de presas, o efeito do tipo de habitat, sexo e tamanho do corpo sobre a dieta de indivíduos de Ameerega braccata, uma espécie da família Dendrobatidae ainda pouco conhecida. Os espécimes foram observados e coletados na localidade tipo, Chapada dos Guimarães e em Cuiabá, Mato Grosso, centro-oeste do Brasil. As categorias de presas mais importantes nos estômagos de A. braccata foram Formicidae, Isoptera e Acari, cujos representantes foram capturados por forrageamento ativo. Os indivíduos da população de Chapada dos Guimarães consumiram mais Acari e menos Isoptera do que os indivíduos da população de Cuiabá, mas os valores de amplitude de nicho foram estreitos e similares entre as duas Braz. J. Biol., 2011, vol. 71, no. 1, p. 189-196 189 Forti, LR. et al. populações. Indivíduos de diferentes tipos de habitat (campo sujo e cerrado stricto sensu) apresentaram diferenças na dieta, como um provável efeito da distinta disponibilidade de presas em cada um dos habitat. Fêmeas consomem mais Isoptera do que os machos. A variação no tamanho do corpo não exerce efeito sobre o número de categorias de presas consumidas. Abundância e volume de ácaros consumidos são significativamente relacionados com o tamanho do corpo dos indivíduos. Os principais resultados sugerem que Ameerega braccata tem estreita amplitude de nicho e dieta especializada em formigas, cupins e ácaros, corroborando a ideia de associação entre este último item e a presença de alcaloides na pele de espécies da família Dendrobatidae. Poucos autores encontraram diferenças entre sexos no consumo de presas por anuros. Diferenças na composição da dieta entre jovens e adultos, entretanto, são frequentes e podem ser consideradas uma característica conservativa, que impede a competição intraespecífica entre classes etárias. Palavras-chave: Ameerega braccata, largura de nicho, Anura, Dendrobatidae, dieta. 1. Introduction Aspects of feeding habits of amphibians have been Cuiabá, Midwestern Brazil? 2) Is this a specialised or a intensively studied (e.g., Strüssmann et al., 1984; Lima and generalised species regarding prey selection? 3) What Magnusson, 1998; Lima, 1998; Van Sluys and Rocha, 1998; feeding strategies are employed in prey capture? 4) Are Van Sluys et al., 2001; Lima et al., 2002; Vaz-Silva et al., there any effects of habitat type, sex, and body size on the 2005; Jordão-Nogueira et al., 2006; Siqueira et al., 2006; diet of A. braccata? Almeida-Gomes et al., 2007a,b), which is certainly related to the outstanding trophic role played by these 2. Material and Methods organisms in many ecological systems. The majority of amphibian species is considered generalist regarding diet, 2.1. Study area and opportunistic regarding prey selection (Duellman and The field work was conducted in two localities, only Trueb, 1994; Teixeira and Coutinho, 2002; Santos et al., 9 km away from one another, but situated in two distinct 2004). Therefore, for the majority of species, the spectrum municipalities from the State of Mato Grosso, Midwestern of dietary items is wide, and reflects the availability of prey Brazil: Chapada dos Guimarães (approximately 15° 24’ S items in the environment (Giaretta et al., 1998; Santos et al., and 55° 50’ W; 650 m a.s.l.) - the type-locality of the species, 2004). However, many other features may influence prey and Cuiabá (approximately 15° 20’ S and 55° 53’ W; consumption, such as foraging strategies (wide foraging 250 m a.s.l.). Data collection occurred in the wet season, versus ambush predation), spatial and temporal variations, from October 2007 to March 2008. Forty-four individuals sex, ontogeny, and body size (Strüssmann et al., 1984; were found in two open physiognomies of the Cerrado Biavati et al., 2004). ecosystem (Figure 1): campo sujo, mainly composed of The Dendrobatidae family includes 169 recognised grasses and sparse tall shrubs, and cerrado stricto sensu, species of mainly diurnal anurans distributed on the where small trees are sparsely present in the landscape. For Amazonian rain forest (Frost, 2009). These frogs are a more detailed description of the sampled physiognomies poisonous, have specialised diets, mainly composed of see Conceição (2000). ants, termites, and mites (Toft, 1980; Caldwell, 1996; The annual mean precipitation in Chapada dos Guimarães Lima et al., 2002; Santos et al., 2003; Biavati et al., ranges from 1,800 to 2,000 mm, and the mean temperature, 2004), and are species are characterised by their bright from 22.8 °C in July, to 27.2 °C, in October (Pinto and colouration and potent skin toxins (Lötters et al., 2000). Hay, 2005). In Cuiabá, the climate is nearly the same as In many species of dendrobatids, a close association has in Chapada, semi-humid (Aw in Köppen’s classification, been found between selected prey items and such skin see Nimer, 1979), with two well defined seasons: a toxic substances, suggesting that they are sequestered from cold and dry season (from April to September), and a diet (e.g., Dumbacher et al., 2004; Mortari et al., 2004; warm and wet season, from October to March each year Takada et al., 2005. See also Darst et al., 2005). (Diniz et al., 2008), with a mean temperature of 25 °C Ameerega braccata (Steindachner, 1864) is a colorful (Schreiner et al., 2009). dendrobatid distributed in the savannah-like Cerrado ecosystem from Central and Midwestern Brazil, where 2.2. Data collection it is known from localities in the States of Mato Grosso, Feeding strategies, location, and the period of feeding Mato Grosso do Sul, and Goiás (Frost, 2009). A few of individuals of Ameerega braccata were observed during aspects of the natural history of this species have already 100 hours by using focal animal method (Altmann, 1974). been addressed (Haddad and Martins, 1994; Forti et al., Dietary items from the stomachs of 44 individuals

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