Fernando A. S. Fernandez

Population dynamics of the marsupial Micoureus demerarae in small fragments of Atlantic Coastal Forest in Brazil

Patterns of population fluctuation, reproductive activity and age structure were studied in populations of the marsupial Micoureus demerarae occupy- ing two small (7.0 and 8.8 ha) fragments of Atlantic Coastal Forest in southeastern Brazil, from 1995 to 1998. Males, but not females, were observed to move between populations. Estimated sizes of the populations in each fragment were very small, usually below 20 individuals. Breeding usually occurred from September to April. Population peaks came mostly by the end of this season, the delay reflecting the time required for the young to become trappable. In August 1997, the area was hit by a fire severely affecting the smaller fragment. Populations were synchronous before the fire, although they became asynchronous after it, possibly in the short term only. Small population sizes, synchrony and presumable male-biased migra- tion are all likely to make the set of populations more vulnerable to extinction than expected for a metapopulation.

Diet of the Marsupial Micoureus demerarae in Small Fragments of Atlantic Forest in Southeastern Brazil

The diet of the marsupial Micoureus demerarae was studied from fecal samples obtained from live-trapping in Atlantic Coastal Forest fragments at Poço das Antas Biological Reserve, southeastern Brazil, from 1995 to 1997. Among arthropods, the most frequent food items belonged to the orders Coleoptera and Hymenoptera, whereas Arachnida, Orthoptera, Hemiptera and Lepidoptera were also frequent. Lepidoptera and Diptera were represented mostly by larvae and pupae. Crustaceans of the orders Copepoda and Isopoda were also found. Plants were represented by seeds of species from secondary vegetation, mostly belonging to the families Piperaceae, Moraceae and Cecropiaceae, which should reflect frugivory. Predominance of arthropods in the diet was consistent with previous studies. Diet composition was remarkably constant among fragments, sexes, age classes, breeding versus non-breeding seasons, and climatic categories (dry versus humid months). The only significant difference was that diversity of arthropods was higher in the non-breeding than in the breeding season, but this was likely to be due to sampling effects. Given the natural abundances of the food items, the constancy of the diet is likely to reflect opportunism rather than food selection.

Population dynamics of small rodents in a grassland between fragments of Atlantic Forest in southeastern Brazil

Summary Population dynamics and reproduction of four species of muroid rodents ( Akodon cursor , Bolomys lasiurus , Oligoryzomys nigripes , and Mus musculus ) were studied through capture-mark-recapture in a grassland between fragments of Atlantic Forest from March 1998 to February 1999. A. cursor and B. lasiurus accounted together for 93.5% of all captures. O. nigripes and M. musculus reached highest population sizes by the end of the dry season. A. cursor was most abundant during late drysol;early wet season, however, its population sizes were higher in the wet season than in the dry season. Populations of B. lasiurus were highest during the dry season, although their population levels varied less than those of A. cursor . The differences in the pattern of population fluctuations of the two latter species can be explained by differences in their feeding habits, as B. lasiurus feeds mostly on grass seeds (most abundant during the dry season), whereas the diet of A. cursor includes a high proportion of insects, which are most abundant during the wet season.

Use of a fragmented landscape by three species of opossum in south-eastern Brazil

Spatial patterns presented by the opossums Caluromys philander , Philander frenata and Micoureus demerarae were studied, through radio-tracking, in a landscape composed of eight small (1.3–13.3 ha) forest fragments surrounded by a matrix of open vegetation in south-eastern Brazil. Sixteen individuals were fitted with radio-collar transmitters and monitored for 2–8 mo. Fixes were obtained by the ‘homing-in on the animal’ technique. Numbers of locations of each individual varied from 6 to 117. Home ranges sizes ranged from 2.5–7.0 ha for C. philander , 0.6–7.4 ha for P. frenata and 0.8–1.7 ha for M. demerarae . Fragments, both edges and interiors, were used more often than the matrix; they are the primary habitat for these marsupials in the landscape. The matrix was used for foraging by P. frenata and C. philander , and traversed in five movements between fragments by P. frenata . Ability to use fragment edges and the matrix is important in explaining how these marsupials are able to persist in the landscape.

ECOLOGY OF THE WATER OPOSSUM CHIRONECTES MINIMUS IN ATLANTIC FOREST STREAMS OF SOUTHEASTERN BRAZIL

Abstract We studied the population structure, spatial patterns, and activity patterns of the water opossum (Chironectes minimus) via capture–mark–recapture and radiotelemetry from October 2004 to October 2006 in Atlantic Forest streams in southeastern Brazil. We tested the hypothesis of reproductive seasonality, the usual pattern in neotropical marsupials, by examining recruitment of juveniles. The hypothesis was rejected, supporting the alternative hypothesis that breeding by water opossums was better explained by its habitat characteristics and prey availability than by its phylogenetic ancestry. The observed sex ratio was significantly biased toward males. The home lengths of individual water opossums varied from 844 to 3,724 m. Males had larger home lengths than females, and there were male–male and male–female overlaps. The longer home lengths for males may explain the observed sex ratio bias, because males are more exposed to capture. All individuals used stream stretches with preserved riparian forest, fast-flowing water, and stony substrate. The hypothesis that activity was homogeneously distributed throughout the night was rejected; activity began right after sunset and ended before sunrise, but with higher levels of activity in the first 6 h of the night. Because of anthropogenic alterations of hydrographic basins, water opossums may be threatened by reduction of their main habitat, streams with fast-flowing water and stony substrate.

Patch relative importance to metapopulation viability: the neotropical marsupial Micoureus demerarae as a case study

As metapopulation dynamics is thought to play an important role in the conservation of mammals, mainly owing to the fragmentation process, a Population Viability Analysis (PVA) was used to evaluate the role and importance of individual patches to the metapopulation persistence of the long-furred wooly mouse opossum, Micoureus demerarae, a neotropical arboreal marsupial. The metapopulation under study comprises eight small Atlantic Forest patches at Poco das Antas Biological Reserve, southeastern Brazil. The analysis indicates that the local populations may be divided into three groups: (1) in the smallest and most isolated patches, where they are the most endangered, (2) in five circular-shaped and relatively well-connected patches and (3) in the largest patch with the most persistent local population. Knowledge of how specific patches influence metapopulation dynamics is an important tool in guiding management strategies, and dynamics can be affected by factors like patch size and relative position. It seems that for this particular case, probability of metapopulation extinction, mean metapopulation size, heterozygosity and mean growth rate were the most informative measures to evaluate a patch’s contribution to metapopulation persistence. Despite all controversies, metapopulation theory, when carefully and properly applied, is a valuable tool in conservation biology.

Influence of edge and fire-induced changes on spatial distribution of small mammals in Brazilian Atlantic forest fragments

The spatial distribution of small mammals in relation to distance from forest edges, before and after fire, was studied in Atlantic Forest fragments in Brazil. None of nine species was captured exclusively on either edges or forest interior. Before the fire only the rodents Akodon cursor and Oecomys con-color were captured more often at the edge than randomly expected. After the fire only A. cursor remained associated with edges; it had increased in number and penetrated farther than before into the forest fragments. The marsupial Micoureus demerarae became more restricted to the forest interior than randomly expected. These results suggest that small mammal species tolerant to habitat changes induced by edge effects and fire have better chances to survive in forest fragments.

Population Dynamics and Conservation Status of the Insular Cavy Cavia intermedia (Rodentia: Caviidae)

Abstract Cavia intermedia may be the mammal with the smallest geographical distribution in the world, because it is endemic to a 10-ha island and therefore vulnerable to extinction. The objective of this study was to understand the population dynamics of C. intermedia in order to define its conservation status and to provide information for its management. The population was sampled monthly using capture–mark–recapture methods and radiotelemetry for 16 months, between March 2004 and June 2005. A total of 5,530 trap-nights resulted in 665 captures of 141 individuals. The population exhibited the main demographic characteristics of the insular syndrome, such as high and stable density, small home ranges, stable age structure composed mostly of adults, and high survival rates. The population dynamics were characterized by density-dependent effects on mortality. C. intermedia can be considered one of the rarest species on the planet because of its limited geographic distribution and very small population size (average estimated population of 42 individuals). We recommend that it be listed as Critically Endangered.

Short-Term Success in the Reintroduction of the Red-Humped Agouti Dasyprocta Leporina, an Important Seed Disperser, in a Brazilian Atlantic Forest Reserve

Reintroduction is an increasingly important tool to restore local extinctions and ecological interactions. Evaluating the success of reintroduction projects allows conservationists to learn from previous experience. Here we report on the reintroduction of agoutis, Dasyprocta leporina, to a Brazilian Atlantic Forest reserve in order to (1) determine the short-term status of the reintroduction; (2) describe and evaluate the management procedures that contributed to reintroduction success; and (3) identify the fruits and seeds consumed and buried by the agoutis, as an indication of their role in restoring ecological processes. We captured and tagged 21 adult individuals from a semi-captive population and reintroduced four males and seven females. One male died and almost all individuals lost weight (range=0-620 g; n=11) during quarantine (median=133 days; range=67–243 days; n=20). Six males and three females died, but the others gained weight during acclimatization (range=150–260 g; n=5). Individuals abandoned the food supplement up to 87 days after release, establishing home-ranges at least three times larger than in natural populations of agoutis. The estimated annual survival rate was 0.83, and 10 nature-born cubs were observed. The reintroduction was considered successful in the short-term. Among the main recommendations for future reintroductions, we suggest the reduction of quarantine and the maintenance of acclimatization periods, with structural improvements for both. Agoutis were seen eating fruits and seeds of 10 species and burying seeds of three of them. The buried seeds are from zoochoric large-seeded trees, thus enhancing recruitment in a disperser-impoverished forest.

Preventing injuries caused by radiotelemetry collars in reintroduced red-rumped agoutis, Dasyprocta leporina (Rodentia: Dasyproctidae), in Atlantic Forest, southeastern Brazil

Reintroduction has been recognized as a powerful conservation tool, but in order to ensure its success, animal monitoring is highly recommended. One way to monitor released animals is to put radiotelemetry collars on them. These devices, however, can harm the subjects, causing serious wounds. Our objectives in this work were to describe the injuries caused by a radiotelemetry collar model on reintroduced agoutis and to propose modifications to it. We equipped agoutis with TXE-311C radio collars (Telenax Wildlife Telemetry) before releasing them in the wild. They acquired serious wounds and one animal died. We then modified the collar structure to reduce its width and retention of water. After these modifications, the injuries did not occur again. As reintroduction is an expensive conservation strategy, any improvement that maximize its probability of success is important. We believe that the improvements we propose here have the potential to enhance the success of reintroductions and to increase animal welfare. This recommendation is more important when captive animals are re-introduced, because they tend to have lower immunity, particularly when they are released in rainy habitats.