Habitat use affects food intake, reproductive fitness and body temperature control in reptiles. Habitat use depends on both the characteristics of the animal and the environmental heterogeneity. In this study we investigated habitat use in a population of the South-American rattlesnake, Crotalus durissus, in a cerrado (the Brazilian savanna) remnant, in southeastern Brazil. In general, snakes appeared to be thermal generalists. However, they showed substrate temperature preferences in the rainy season, when they selected colder substrates during the day and warmer substrates at night. Individuals were predominantly active on the surface and more frequently found under bushes. Furthermore, in general, the principal component analysis results indicate that rattlesnakes are generalists regarding the microhabitat variables examined in this study. These habitat characteristics, associated with a low thermal selectivity, indicate that rattlesnakes are able to colonize deforested areas where shade occurrence and vegetation cover are similar to those in the cerrado.

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Farming practices may reshape the structure of watersheds, water quality, and the health of aquatic organisms. Nutrient enrichment from agricultural pollution increases disease pressure in many host–pathogen systems, but the mechanisms underlying this pattern are not always resolved. For example, nutrient enrichment should strongly influence pools of aquatic environmental bacteria, which has the potential to alter microbiome composition of aquatic animals and their vulnerability to disease. However, shifts in the host microbiome have received little attention as a link between nutrient enrichment and diseases of aquatic organisms. We examined nutrient enrichment through the widespread practice of integrated pig–fish farming and its effects on microbiome composition of Brazilian amphibians and prevalence of the globally distributed amphibian skin pathogen Batrachochytrium dendrobatidis (Bd). This farming system drove surges in fecal coliform bacteria, disturbing amphibian skin bacterial communities such that hosts recruited higher proportions of Bd-facilitative bacteria and carried higher Bd prevalence. Our results highlight previously overlooked connections between global trends in land use change, microbiome dysbiosis, and wildlife disease. These interactions may be particularly important for disease management in the tropics, a region with both high biodiversity and continually intensifying anthropogenic pressures on aquatic wildlife habitats.

Anurans exhibit limited dispersion ability and have physiological and behavioural characteristics that narrow their relationships with both environmental and spatial predictors. So, the relative contributions of environmental and spatial predictors in the patterns of taxonomic and functional anuran beta diversity were examined in a metacommunity of 33 ponds along the coast of south Brazil. We expected that neutral processes and, in particular, niche-based processes could have similar influence on the taxonomic and functional beta diversity patterns. Distance-based methods (db-RDA) with variation partitioning were conducted with abundance data to examine taxonomic and functional facets and components (total, turnover and nestedness) in relation to environmental and spatial predictors. Processes determining metacommunity structure differed between the components of beta diversity and among taxonomic and functional diversity. While taxonomic beta diversity was further accounted by both environmental and spatial predictors, functional beta diversity responded more strongly to spatial predictors. These two contrasting patterns were different to what we had predicted, suggesting that while there is a taxonomic turnover mediated by environmental filters, the spatial distance promotes the trait dissimilarity between sites. In addition, our data confirm that neutral and niche-based processes operate on anuran metacommunities even at short geographic scales. Our results reinforce the idea that studies aiming to evaluate the patterns of structure in metacommunities should include different facets of diversity so that better interpretations can be achieved.

Predation is the major selective force that drives the development of a series of defense mechanisms by the species. These mechanisms are efficient in that it limits the ability of predators to detect, recognize and subdue their prey. In lizards for example, the tail loss and locomotor escape are the most common defensive behavior reported on the literature. Additionally, in response to external stimuli, some lizards exhibit a peculiar defensive behavior: death-feigning or thanatosis. Here we describe the first record of death-feigning in a population of Liolaemus occipitalis in a coastal sand dune habitat in Southernmost Brazil. A total of 86 individuals were tested. During handling 75.6% of lizards feigned death. The duration of this behavior was longer when the observer remained closer to the lizards, suggesting the ability of L. occipitalis to evaluate the predation risk. Resumo: A pressão exercida pela predação é a principal força seletiva que direciona o estabelecimento de uma série de mecanismos de defesa por parte das espécies. Esses mecanismos são eficientes na medida em que limitam a capacidade dos predadores em detectar, reconhecer ou subjugar suas presas. Em lagartos, por exemplo, os comportamentos defensivos mais frequentemente citados na literatura são a autotomia caudal e a fuga. Além disso, em resposta a estímulos externos, alguns lagartos podem exibir um comportamento peculiar: fingem-se de mortos (tanatose). Neste estudo descrevemos o primeiro registro de tanatose em uma população de Liolaemus occipitalis em área de dunas costeiras no extremo Sul do Brasil. MethodsThe data presented in this study was collected between November 2009 and January 2010 in the municipality of Rio Grande, RS, in an area known as Balneário Cassino, southernmost Brazil (32º 07' 54.65'' -32º 17' 35.07'' S and 52º 06' 38.80'' -52º 20' 53.36'' W) located at sea level. The area consists of well preserved wet habitats formed by meadows with a mosaic of dunes, sand dune vegetation and temporary lagoons. The climate is classified as subtemperate (Maluf 2000), with an average annual maximum temperature of 23.3 °C and average annual minimum temperature of 12.7 ºC. The seasons are well defined, with rainfall homogeneously distributed along the year and averaging 1252 mm between 1931and1990 (INMET 2010). During field surveys of the regional herpetofauna, we captured 86 individuals of Liolaemus occipitalis using pitfall traps with drift fences (Brasileiro et al. 2005). The lizards remained a maximum of eight hours in buckets containing water and shelter to protect them against the sunlight, minimizing the stress on captured animals. All lizards were handled carefully during measurements (body size and mass), sex determination, and assessment of the reproductive condition of females by palpation (Fitch 1987). While being held, some individuals feigned death (Figure 1). The animals that exhibited this behavior were immediately placed on the ground and observed from two distances, 1 and 7 m, whose order was set at random....

doi: bioRxiv preprint length suggests differences in dispersal and trophic segregation between species.

The ability of a species to defend itself against a predator is directly correlated with its survivorship. Thus, prey/predator interaction mechanisms are important elements of the natural history of species. In this study, we examined the defensive repertoire of the South-American hognose snake (Xenodon dorbignyi) through simulations of predator attacks in the field. Nine defensive displays were observed. The most frequently observed displays were erratic movements, body flattening, head triangulation and tail display. No differences were detected in the defensive strategies shown by males and females, regardless of their reproductive state. Our findings suggest that X. dorbignyi has the ability to evaluate the level of threat imposed by the aggressor, with cryptic behavior, body flattening and locomotor escape as the primary defensive strategies, with other displays used as secondary responses to a predator attack. Our results support the hypothesis that X. dorbignyi is a mimic of both Micrurus and Bothrops.

Pseudis minuta is abundant in a variety of aquatic environments of the Pampa domain. Therefore, it can be considered a good model for testing hypotheses on environmental heterogeneity and the influence of climate on the activity of anurans. In this study, we examined the spatial distribution pattern of P. minuta in terms of microhabitats and the influence of abiotic factors on seasonal fluctuations in the abundance of this species. Samples were collected monthly from April 2008 to May 2009 in wetlands and coastal dunes in the Lagoa do Peixe National Park. A total of 112 specimens of P. minuta were collected, of which 45 were found in the wetland area and 67 in the dune area. The species showed seasonal fluctuation in abundance, and it was most abundant in months with higher temperatures (spring-summer). Pseudis minuta was mainly associated with aquatic vegetation, an expected pattern in terms of their morphological adaptations to this environment. Among the abiotic parameters analyzed, only the monthly mean temperature showed a significant correlation (p < 0.05; r = 0.67) with the abundance of P. minuta. We concluded that P. minuta is a generalist species with respect to microhabitat use and also that fluctuation in its population abundance is mainly associated with seasonal variation in temperature.Keywords: abundance, anuran, coastal plain, Lagoa do Peixe, spatiotemporal distribution.Padrão de atividade e uso de micro-habitat de Pseudis minuta Günther, 1858 (Anura, Hylidae) no Parque Nacional da Lagoa do Peixe, uma reserva da biosfera na região subtropical do Brasil ResumoPseudis minuta é uma espécie abundante em diferentes tipos de ambientes aquáticos do domínio Pampa. Por essa razão, essa espécie pode ser considerada um bom modelo para testar hipóteses relacionadas à heterogeneidade ambiental e à influência do clima sobre padrões de atividade em anuros. Neste trabalho, foi avaliado o padrão de distribuição espacial de P. minuta em termos de micro-habitats, além de se avaliar a influência de fatores abióticos nas flutuações sazonais da abundância dessa espécie. Coletas foram realizadas mensalmente, entre abril de 2008 e maio de 2009, em áreas úmidas e de cordões de dunas costeiras no Parque Nacional de Lagoa do Peixe. Um total de 112 indivíduos de P. minuta foi coletado, sendo 45 em áreas de banhado e 67 em área de dunas. A espécie apresentou flutuação sazonal na abundância, sendo mais abundantes em meses com temperaturas mais elevadas (primavera-verão). Pseudis minuta esteve associada principalmente à vegetação aquática, um padrão esperado em função de suas adaptações morfológicas a esse meio. Entre os parâmetros abióticos analisados, somente a temperatura média mensal apresentou correlação significativa (p < 0.05; r = 0,67) com a abundância de P. minuta. Foi possível concluir que P. minuta é uma espécie generalista com relação ao uso do habitat e que as flutuações na sua abundância populacional estão principalmente associadas à variação sazonal da temperatura.Palavras-chave: abundância, anuro, planí...