14 research outputs found
Availability of food resources and habitat structure shape the individualâresource network of a Neotropical marsupial
1. Spatial and temporal variation in networks has been reported in different studies.
However, the many effects of habitat structure and food resource availability variation
on network structures have remained poorly investigated, especially in individualâ
based networks. This approach can shed light on individual specialization
of resource use and how habitat variations shape trophic interactions.
2. To test hypotheses related to habitat variability on trophic interactions, we investigated
seasonal and spatial variation in network structure of four populations of
the marsupial Gracilinanus agilis in the highly seasonal tropical savannas of the
Brazilian Cerrado.
3. We evaluated such variation with network nestedness and modularity considering
both coolâdry and warmâwet seasons, and related such variations with food resource
availability and habitat structure (considered in the present study as environmental
variation) in four sites of savanna woodland forest.
4. Network analyses showed that modularity (but not nestedness) was consistently
lower during the coolâdry season in all G. agilis populations. Our results indicated
that nestedness is related to habitat structure, showing that this metric increases
in sites with thick and spaced trees. On the other hand, modularity was positively
related to diversity of arthropods and abundance of fruits.
5. We propose that the relationship between nestedness and habitat structure is an
outcome of individual variation in the vertical space and food resource use by
G. agilis in sites with thick and spaced trees. Moreover, individual specialization in
resourceârich and populationâdense periods possibly increased the network modularity
of G. agilis. Therefore, our study reveals that environment variability considering
spatial and temporal components is important for shaping network
structure of populations
Ecology and natural history of Akodon lindberghi (Rodentia, Sigmodontinae) in southeastern Brazil
We studied the ecology and natural history of the globally threatened and poorly known Akodon lindberghi Hershkovitz, 1990 in Parque Nacional da Serra da Canastra (PNSC) and Juiz de Fora (JF), southeastern Brazil. From November 1998 to September 2001 a total of 131 individuals were captured in wire-cage live-traps and 52 by pitfalls traps. They were all marked and released at the site. The largest abundances were registered during the dry season, and most of the captures occurred in open habitats. The mean body mass of the two populations was significantly different (18.1 g at PNSC versus 13.1 g at JF; H = 46.2678, g.l.=2, p<0.001). In PNSC, individuals were reproductively active from August to February, and juveniles were present from May to August. The results suggest that the changes in vegetation structure caused by deforestation and intensive agricultural activities could increase the predation rate, affecting the mean body mass of the population
Terrestrial Small Mammal Richness and Habitat Associations in an Amazon Forest-Cerrado Contact Zone1
Diet of the gracile mouse opossum Gracilinanus agilis (Didelphimorphia: Didelphidae) in a neotropical savanna: intraspecific variation and resource selection.
Investigation of the effect of endogenous and exogenous factors on the diet of animals is necessary for a better understanding of their feeding habits. This approach can provide relevant information on the autoecology of a species and its ecological interactions. We investigated the composition and intraspecific variation in the diet of the marsupial Gracilinanus agilis in areas of dry woodland forests (i.e., cerradĂŁo) in the Cerrado of Central Brazil, taking into consideration the availability of prey (arthropods) in the environment. We found insects, spiders, birds, and fruits in the scats of G. agilis. Insects (orders Hymenoptera, Isoptera, Hemiptera, and Coleoptera) and fruits were the most frequently consumed resources. Males fed more heavily on insects than females did, whereas during the warm?wet season (October to April), the reproductive females fed on insects more than the nonreproductive females did. On the other hand, the consumption of fruits and vertebrates did not vary between seasons, sexes, or according to female reproductive condition. Moreover, reproductive females fed more frequently on ants and beetles than nonreproductive females did. We also detected both positive (for Isoptera and Hemiptera) and negative (for Hymenoptera) selection of insects during the cool?dry season, whereas in the warm?wet season, these resources were consumed according to their availability in the environment. Our study revealed that G. agilis is an insectivore?omnivore species, but fruits also are a relevant part of its diet. This marsupial seemed to select their prey qualitatively according to its energy demands and nutritional requirements