Françoise Bayart

Total Energy Expenditure and Body Composition in Two Free-Living Sympatric Lemurs

Background Evolutionary theories that account for the unusual socio-ecological traits and life history features of group-living prosimians, compared with other primates, predict behavioral and physiological mechanisms to conserve energy. Low energy output and possible fattening mechanisms are expected, as either an adaptive response to drastic seasonal fluctuations of food supplies in Madagascar, or persisting traits from previously nocturnal hypometabolic ancestors. Free ranging ring-tailed lemurs (Lemur catta) and brown lemurs (Eulemur sp.) of southern Madagascar have different socio-ecological characteristics which allow a test of these theories: Both gregarious primates have a phytophagous diet but different circadian activity rhythms, degree of arboreality, social systems, and slightly different body size. Methodology and Results Daily total energy expenditure and body composition were measured in the field with the doubly labeled water procedure. High body fat content was observed at the end of the rainy season, which supports the notion that individuals need to attain a sufficient physical condition prior to the long dry season. However, ring-tailed lemurs exhibited lower water flux rates and energy expenditure than brown lemurs after controlling for body mass differences. The difference was interpreted to reflect higher efficiency for coping with seasonally low quality foods and water scarcity. Daily energy expenditure of both species was much less than the field metabolic rates predicted by various scaling relationships found across mammals. Discussion We argue that low energy output in these species is mainly accounted for by low basal metabolic rate and reflects adaptation to harsh, unpredictable environments. The absence of observed sex differences in body weight, fat content, and daily energy expenditure converge with earlier investigations of physical activity levels in ring-tailed lemurs to suggest the absence of a relationship between energy constraints and the evolution of female dominance over males among lemurs. Nevertheless, additional seasonal data are required to provide a definitive conclusion.

Diet, Nutritional Ecology, and Birth Season of Eulemur macaco in an Anthropogenic Forest in Madagascar

We investigated the feeding ecology of Eulemur macaco macaco in an old coastal secondary forest of northwestern Madagascar. We analyzed whether the local combination of introduced and native plant species could provide viable anthropic conditions for sustaining the black lemurs. Fruits (79 spp.) dominated the annual diet (>104 species from 50 families via observations ad libitum and use of a feeding frequency methods). Records from the early dry (mating) and late dry (birth) seasons show that a few major fruit species are staples in conjunction with a variety of other plant items in much lower proportions. We further estimated daily food intake and analyzed nutrient/antinutrient content in the diet during the birth season to evaluate the possibility that black lemurs undergo nutritional stress. They exhibited a high-energy input/low energy output foraging strategy then and had limited use of alternative resources such as leaves throughout the study period. We conclude that the potential for feeding flexibility is low because specialization on fruit results in protein requirements being achieved probably by a narrow margin. We hypothesize that patchy distribution of preferred cash-crop plants and indigenous species currently has a major limiting effect on population size through feeding competition.

Densités de primates en forêt guyanaise. Test d'une méthode d'estimation par transect

Abstract The results of a classical transect method designed to evaluate primate density are compared with estimates obtained from long-term studies on three species within a community inhabiting an undisturbed rain forest (French Guiana). Combining results of both methods, the total density of the primate community, which includes six species, is about 70 individuals per square kilometre. The concordance of data noted in Alouatta seniculus, Cebus apella and Saguinus midas , makes the transect method a reliable approach to low primate densities overall. However, it requires that long cumulative distances are walked and does not guarantee that rare species will not be missed. The predominance of Alouatta within the community, as observed in numerous Amazonian communities, is interpreted in relation to the nutritional quality of its environment and weak feeding competition between primate species.

Diet and Population Densities of the Primate Community in Relation to Fruit Supplies

Field studies in recent decades have shown that idea of an overabundance of food for consumers in tropical evergreen rainforests is too simplistic (e.g. Milton 1980, Terborgh 1986). There is considerable evidence of difficulties encountered by animals when seeking foods. Among these, food availability is known to vary between locations, seasons and years, often in an unpredictable manner (e.g. Sabatier 1985). Plant defences against consumers can reduce access to nutrients in subtle ways. For example, leaf allelochemicals may vary qualitatively and quantitatively according to light exposure within a single tree (Waterman & Kool 1994) and in relation to herbivore pressure (Feeny 1970). Following such variability in food availability, fluctuations in food choices and nutrient intake throughout the year are the rule among primates (Hladik 1988). In this context, species exhibit a wide variety of feeding strategies, depending on specific metabolic needs, digestive efficiency, sensory perception of the environment and cognitive abilities, sometimes leading to the development of feeding traditions (Hladik & Simmen 1996). Although primate species are variously constrained in their niche breadth (Milton 1981), it has become clear, in view of these findings, that primate diets are best described as flexible (Gautier-Hion et al. 1993).

Post-Dispersal Seed Removal in Four Frugivore-Dispersed Tree Species

In Neotropical forests, a majority of plant species relies upon arboreal and flying frugivores for the dispersal of their seeds (Howe 1986, Howe & Smallwood 1982, Charles-Dominique Chapter 17). Once the fruits are consumed and the pulp or arillote digested, seeds are either regurgitated or dropped into faeces below the parent tree or a conspecific tree, a nearby perch tree or along canopy routes frequently used by animals (Howe 1989, Howe 1993, Julliot 1996, Julliot 1997, Schupp et al. 1989). As animals move along pathways in the canopy or fly over trees within their home range seeking other fruit sources, they may forage into forest areas where the previously consumed tree species is at low density or absent (van Roosmalen 1985). Given the retention time in the stomach and gut, and habit of frugivores, seeds may thus be dropped below the parent tree crown, in the parent neighbourhood, or farther away from any conspecific tree (Julliot 1997). Consequently, seeds may be deposited in areas varying in the density of the dispersed tree species (Schupp 1992).