" Vasey (this study), Balko (1998), and Ratsimbazafy (2002) sampled contiguous months over entire annual cycles. Morland (199 la,b) sampled 10 months over an 18-month period, excluding the hot rainy/lactation months of Feb and Mar. Rigamonti (1993) sampled seven contiguous months (May-Nov), excluding most hot months of the year. Britt (1997) sampled seven contiguous months (Jan-Jul), including both some hot and cold months. White (1991) sampled only two contiguous cold rainy months (Jun-Jul). Petter's (1962) characterization of sociality in Varecia was based on brief surveys at the sites of Perinet, Fanovana, Ambodiriana in the months of Jul and Oct.
11 Only one aspect of social structure is treated and summarized here: group structure (size and age-sex composition). Another aspect of social structure, namely, population structure (e.g., density), is treated and reviewed for the genus Varecia in Vasey (1997c, 2003).
' Ratsimbazafy's (2002) study focused on the effects of cyclone disturbance on V. rariejjata ecology in a lowland rainforest fragment. Precyclone group sizes at this site were larger (4-8 individuals).
d Broad surveys on Nosy Mangabe provide home range estimates of 30 ha per community, whereas measurements around the perimeter of Morland's study community provide the much smaller estimate of 8.5 ha.
may include differences in population density, resource distribution, the presence of other diurnal, frugivorous lemurs, and perhaps hunting pressure. In a particular region, several of these factors could make defense of a territory, and the resources in it, unprofitable or excessively costly (Krebs and Davies, 1993). Plant resources used by V. rubra at Andranobe may prove exceptionally dense and species-rich relative to other rainforests in Madagascar (Vasey, 2000b) and largely explain how such a large community and dense population can be supported within a 57.7-ha home range.
In summary, the ranging pattern of V. rubra, especially that of females, shifts during the year consistent with the hypothesis that they would conserve energy during the food-scarce cold rainy season and during energetically costly reproductive stages by minimizing forest area used and distances traveled. Sex differences in ranging correspond to differing reproductive investment by females and males. However, both sexes travel longer daily distances during female lactation than during gestation. This may reflect the ruffed lemur's absentee parenting system and high male parental investment. The ranging pattern and, in turn, the fission-fusion social organization of V. rubra appear, therefore, to be the outcome of its reproductive biology combined with its reliance on a spatiotemporally patchy diet. This fission-fusion social system has two components, a daily component and a higher-level component dictated both by seasonality and by reproduction. Where comparisons with other studies of wild Varecia are possible, similar seasonal ranging patterns are observed despite variation in community size, home range area, and territoriality.
These summary points suggest a future path of inquiry—one that would more tightly link the least variable (or invariable) ecological traits of ruffed lemurs (such as seasonal ranging patterns, fission-fusion social organization, and reliance on ephemeral rainforest foods) with their suite of reproductive traits, in particular their unusual parenting system. Such an effort will ultimately inform our broader understanding of the evolution and maintenance of traits that are relatively unique to Malagasy lemurs and which ruffed lemurs possess, such as female dominance, the lack of sexual dimorphism, and highly seasonal breeding.
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