Efeito da suplementação alimentar no uso do espaço pelo marsupial Gracilinanus agilis em fragmentos de Cerradão no Brasil Central

Dissertação (mestrado)—Universidade de Brasília, Instituto de Ciências Biológicas, Departamento de Ecologia, Programa de Pós-Graduação em Ecologia, 2017.A forma com que animais utilizam uma área proporciona diversas informações ecológicas. Eles utilizam o espaço para encontrar alimento, abrigo e para reprodução, mas estão sujeitos a sofrerem os efeitos de predação, competição e de outras interações bióticas. Estudos geralmente mostram que há uma associação negativa entre o uso do espaço e disponibilidade de recurso, mas poucos estudos neotropicais avaliam o efeito da introdução direta e contínua de alimento em populações naturais. O aumento na oferta de alimento pode causar um aumento da densidade populacional associado com uma diminuição da área de uso, devido a necessidade de se percorrer um menor espaço para conseguir alimento. Uma maior concentração de recurso em determinado estrato também pode direcionar a movimentação dos indivíduos escansoriais em uma escala vertical. Eu investiguei possíveis alterações no uso do espaço, pelo marsupial Gracilinanus agilis, causadas por uma introdução experimental contínua de alimento. Para isso, amostrei quatro áreas de cerradão usando grades de captura e armadilhas no estrato do solo e sub-bosque. Duas dessas áreas tiveram adição de alimento através de comedouros que restringiam a entrada de animais maiores do que as do porte de G. agilis. A área de uso média, estimada pelo método dos Mínimos Polígonos Convexos, foi de 0,202 ha ± 0,02, similar ao encontrado por outros estudos com a espécie e com o gênero. A introdução de alimento não influenciou diretamente a área de uso nem a sobreposição destas entre indivíduos vizinhos. No entanto, essa suplementação alimentar levou a um aumento na densidade das populações e uma redução do uso do solo por esses marsupiais. Para G. agilis, o alimento parece não influenciar primariamente o uso do espaço horizontal. Esses pequenos marsupiais se alimentam principalmente de recursos adensados, o que poderia possibilitar a G. agilis não precisar se deslocar por um espaço muito grande para buscar alimento e levar a uma não-redução do mesmo em função da suplementação alimentar. Uma possível redução na área de uso possibilidade pela complementação alimentar pode ter sido compensada pela necessidade dos indivíduos de se descolarem por uma área maior, devido ao aumento na densidade advindo dessa mesma complementação. Além disso, esses pequenos marsupiais são semélparos promíscuos, o que ressalta a importância da busca por parceiros, que pode ser mais determinante para o uso do espaço do que a busca por alimento.The way animals use an area provides many ecological information. They use space to find food, shelter and mating partners, besides suffering from the effects of predation, competition, and other biotic interactions. Studies generally show that there is a negative association between home range and resource availability, but there are few studies in the neotropics evaluating the effect of direct and continuous food supplementation on natural populations. The increase in food supply can cause an increase in population densities associated with a decrease in the home range, caused by a reduction in the foraging area needed for obtaining the individual food requirements. A higher concentration of resource in a given stratum can also direct the movement of scansorial individuals on a vertical scale. I investigated possible changes in the use of space by marsupial Gracilinanus agilis caused by a continuous experimental introduction of food. To do so, I sampled four areas of dry woodland using capture grid and live traps in the ground and understory. Two of those areas had food supplementation through feeders which restrict access from bigger animals then G. agilis. The mean area of home range, estimated by the Minimum Convex Polygon method, was 0.202 ha ± 0.02, similar to that found for congeneric species in other studies. The food supplementation did not directly influence home range size or the overlap of individuals’ home range. This supplementation led to an decrease, however, in ground captures of these marsupials. For G. agilis the food supply did not seem to influence home range primarily. These small marsupials feed mainly on aggregated resources, which could enable G. agilis not to move through large distances when foraging and also resulting in a lack of home-range size reduction after food supplementation. A potential reduction in home-range size caused by the food complementation may have been compensated by the need for a larger foraging area caused by the increase in density caused by this same supplementation. In addition, these small marsupials are promiscuous semelparous, which highlights the importance of searching for partners, which may be more determinant for home range than searching for food

Parasite association in non-volant small mammals in Brazil

Small mammals not only play an important role in biodiversity, but also act as dynamic hosts and reservoirs for a variety of parasites that are of public health importance. Furthermore, host–parasite associations are driven by complex ecological interactions, and the parasite species dynamics are explained by several factors. In this work we aim to verify the association between parasitic infections in small Brazilian mammals. Here, we carried out a systematic review to verify the distribution of parasites in small Brazilian mammals; later we carried out a network analysis to assess the host–parasite associations of the results found. We found 110 studies that included all groups of parasites. We compiled a set of networks with the dif- ferent groups of parasites (except viruses and fungi due to the small number of records). The most widespread host species were Akodon cursor, A. montensis, Clyomys laticeps, Didelphis albiventris, D. aurita, D. marsupialis, Necromys lasiurus, Nectomys squamipes, Oligoryzomys nigripes, Thaptomys nigrita, and Thrichomys fosteri, that occurred in the four networks. All networks had modular patterns, except for Helminth’s network. A phenomenon known as aggregation in parasitology was observed in our review with many associations of small mammals and parasites. Furthermore, rodents and marsupial species are highly diversified and have the potential to be sources of pathogens, directly or indirectly through vectors. Therefore, understanding the host–parasite relationship is essential, not only for the ecological history of the hosts and/or parasites, but also for its importance for public health in disease transmission

An alternative method for determining the body condition index of the free-living South American coati

Assessing and monitoring the welfare of free-living mammals is not a usual process due to the logistical complications associated with their capture and sedation, collection and storage of biological samples and their release. In this context, non-invasive methods for monitoring wildlife constitute a good alternative approach for in situ conservation. Body condition index, as a measurement of health status, has been used in free-living mammals; its low value may be associated with negative effects on reproduction and survival. The present study aimed to generate an alternative and reliable non-invasive method and then determine the body condition index, based on previously-collected biometric measurements, without the need to capture and immobilise the animals. A total of 178 free-living Nasua nasua Linnaeus, 1766 were trapped, weighed and measured. Statistical methods were used, based on Boosted Regression Trees (BRT) using body mass, biometric measurements (body length, height and chest girth) and gender as explanatory variables. To assess the agreement between the real Body Condition Indices (BCIs) and the predicted values of BCIs, we explored the correlation between each model using the Bland-Altman method. This method showed a strong agreement between the predictive BRT models proposed (standardised residuals from a linear regression between body length and chest girth) and standardised residuals (linear regression between body mass and body length). The results obtained herein showed that BRT modelling, based on biometrical features, is an alternative way to verify the body conditions of coatis without the need to capture and immobilise the animals