RESUMO
Abstract Here we inferred about the effectiveness of a buffer zone composed by an Agroforestry System (AS) for providing reproductive conditions for Atlantic Forest birds by comparing artificial nest predation rates between a buffer zone, a primary forest area, and a set of small and isolated Atlantic Forest fragments. We have used 237 nests throughout the three areas, of which 100 (42.2%) were depredated. Predation frequencies were 28.6% in the continuous forest, 100% in the AS, and 51.9% in the fragments, differing significantly. We could detect nest predators in 48 of the 100 depredated nests (48%) using camera traps. Differences between areas may be attributed to changes in nest predator species. We support previous evidences that the conservation of bird communities may not rely on buffer zones as an extension of their breeding habitats.
Resumo O presente estudo teve como objetivo avaliar a efetividade de uma zona tampão composta por um sistema agroflorestal (SA) para a reprodução de aves da Mata Atlântica. Para isto, as porcentagens de predação em ninhos artificiais foram comparadas entre as zonas tampão, uma área de floresta primária e em um conjunto de fragmentos de Mata Atlântica pequenos e isolados. Um total de 237 ninhos foi utilizado nas três áreas e 100 deles (42,2%) foram predados. As porcentagens de predação foram 28,6% na área de floresta primária, 100% no SA e 51,9% nos fragmentos, havendo diferença significativa. Os predadores puderam ser identificados em 48 das 100 predações (48%) com o uso de câmeras trap, o que gerou evidências de que as diferenças possam ser atribuídas a mudanças na composição de espécies de predadores entre as áreas. Esta análise dá suporte a estudos prévios de que as zonas tampão não devam ser consideradas como extensão dos hábitats naturais para a conservação de comunidades de aves.
RESUMO
Habitat size and climate are known to affect the trophic structure and dynamics of communities, but their interactive effects are poorly understood. Organisms from different trophic levels vary in terms of metabolic requirements and heat dissipation. Indeed, larger species such as keystone predators require more stable climatic conditions than their prey. Likewise, habitat size disproportionally affects large-sized predators, which require larger home ranges and are thus restricted to larger habitats. Therefore, food web structure in patchy ecosystems is expected to be shaped by habitat size and climate variations. Here we investigate this prediction using natural aquatic microcosm (bromeliad phytotelmata) food webs composed of litter resources (mainly detritus), detritivores, mesopredators, and top predators (damselflies). We surveyed 240 bromeliads of varying sizes (water retention capacity) across 12 open restingas in SE Brazil spread across a wide range of tropical latitudes (-12.6° to -27.6°, ca. 2,000 km) and climates (Δ mean annual temperature = 5.3°C). We found a strong increase in predator-to-detritivore mass ratio with habitat size, which was representative of a typical inverted trophic pyramid in larger ecosystems. However, this relationship was contingent among the restingas; slopes of linear models were steeper in more stable and favorable climates, leading to inverted trophic pyramids (and top-down control) being more pronounced in environments with more favorable climatic conditions. By contrast, detritivore-resource and mesopredator-detritivore mass ratios were not affected by habitat size or climate variations across latitudes. Our results highlight that the combined effects of habitat size, climate and predator composition are pivotal to understanding the impacts of multiple environmental factors on food web structure and dynamics.
Assuntos
Ecossistema , Cadeia Alimentar , Animais , Brasil , Comportamento PredatórioRESUMO
The diets of six shark species, Sphyrna lewini, Sphyrna zygaena, Carcharhinus obscurus, Carcharhinus limbatus, Rhizoprionodon lalandii and Galeocerdo cuvier, were investigated in a subtropical coastal ecosystem of southern Brazil. Stomach content data were obtained to assess foraging niche segregation and ontogenetic shifts in the diets of these sharks. Five of the shark species off the Paraná coast were ichthyophagous, with the exception of S. zygaena, which was teutophagous. With the exception of G. cuvier, which had a generalist diet, the other five species displayed specialization in their feeding. Ontogenetic shifts were observed in C. obscurus and S. lewini with large individuals consuming elasmobranchs. Owing to the diet overlap between C. obscurus and S. lewini, C. obscurus and C. limbatus and R. lalandii and C. limbatus, future studies on the spatial and temporal distributions of these species are needed to understand the extent of competitive interactions.
Assuntos
Dieta , Cadeia Alimentar , Tubarões , Animais , Brasil , Ecossistema , Comportamento Predatório , Tubarões/classificação , Especificidade da EspécieRESUMO
This study identifies the food habits of the margay, Leopardus wiedii (Schinz, 1821), and the jaguarundi, Puma yagouaroundi (É. Geoffroy Saint-Hilare, 1803), in the Vale do Rio Doce Natural Reserve and in the Sooretama Biological Reserve, Espírito Santo, Brazil. We determined the diet of both species by the analysis of scats. Fecal samples were collected from April 1995 to September 2000 and identified based on the presence of hairs that were ingested during self-grooming. Scats were oven-dried and washed on a sieve, and the screened material was identified using a reference collection. Of the 59 fecal samples examined, 30 were confirmed to be from the margay and nine of them from the jaguarundi. Mammals were the most consumed items in the diet of the margay, occurring in 77% of the fecal samples, followed by birds (53%) and reptiles (20%). Among the mammals consumed, marsupials (Didelphimorphia) were the most common item (66%). In the diet of the jaguarundi, birds were the most consumed items and occurred in 55% of the fecal samples; mammals and reptiles occurred in 41% and in 17% of the fecal samples, respectively. From this work we conclude that the margay and jaguarundi fed mainly upon small vertebrates in the Vale do Rio Doce Natural Reserve and in the Sooretama Biological Reserve. Although sample sizes are therefore insufficient for quantitative comparisons, margays prey more frequently upon arboricolous mammals than jaguarundis, which in turn prey more frequently upon birds and reptiles than margays. This seems to reflect a larger pattern throughout their geographic range
RESUMO
This study identifies the food habits of the margay, Leopardus wiedii (Schinz, 1821), and the jaguarundi, Puma yagouaroundi (É. Geoffroy Saint-Hilare, 1803), in the Vale do Rio Doce Natural Reserve and in the Sooretama Biological Reserve, Espírito Santo, Brazil. We determined the diet of both species by the analysis of scats. Fecal samples were collected from April 1995 to September 2000 and identified based on the presence of hairs that were ingested during self-grooming. Scats were oven-dried and washed on a sieve, and the screened material was identified using a reference collection. Of the 59 fecal samples examined, 30 were confirmed to be from the margay and nine of them from the jaguarundi. Mammals were the most consumed items in the diet of the margay, occurring in 77% of the fecal samples, followed by birds (53%) and reptiles (20%). Among the mammals consumed, marsupials (Didelphimorphia) were the most common item (66%). In the diet of the jaguarundi, birds were the most consumed items and occurred in 55% of the fecal samples; mammals and reptiles occurred in 41% and in 17% of the fecal samples, respectively. From this work we conclude that the margay and jaguarundi fed mainly upon small vertebrates in the Vale do Rio Doce Natural Reserve and in the Sooretama Biological Reserve. Although sample sizes are therefore insufficient for quantitative comparisons, margays prey more frequently upon arboricolous mammals than jaguarundis, which in turn prey more frequently upon birds and reptiles than margays. This seems to reflect a larger pattern throughout their geographic range
RESUMO
This study identifies the food habits of the margay, Leopardus wiedii (Schinz, 1821), and the jaguarundi, Puma yagouaroundi (É. Geoffroy Saint-Hilare, 1803), in the Vale do Rio Doce Natural Reserve and in the Sooretama Biological Reserve, Espírito Santo, Brazil. We determined the diet of both species by the analysis of scats. Fecal samples were collected from April 1995 to September 2000 and identified based on the presence of hairs that were ingested during self-grooming. Scats were oven-dried and washed on a sieve, and the screened material was identified using a reference collection. Of the 59 fecal samples examined, 30 were confirmed to be from the margay and nine of them from the jaguarundi. Mammals were the most consumed items in the diet of the margay, occurring in 77% of the fecal samples, followed by birds (53%) and reptiles (20%). Among the mammals consumed, marsupials (Didelphimorphia) were the most common item (66%). In the diet of the jaguarundi, birds were the most consumed items and occurred in 55% of the fecal samples; mammals and reptiles occurred in 41% and in 17% of the fecal samples, respectively. From this work we conclude that the margay and jaguarundi fed mainly upon small vertebrates in the Vale do Rio Doce Natural Reserve and in the Sooretama Biological Reserve. Although sample sizes are therefore insufficient for quantitative comparisons, margays prey more frequently upon arboricolous mammals than jaguarundis, which in turn prey more frequently upon birds and reptiles than margays. This seems to reflect a larger pattern throughout their geographic range