Niche separation in Varecia variegata rubra and Eulemur fulvus albifrons: II. Intraspecific patterns

Abstract

Based on a year-long field study in northeastern Madagascar, I summarize annual patterns of niche use (food patch size, diet, forest height, and forest site) in two sympatric lemurs, Varecia variegata rubra and Eulemur fulvus albifrons. Furthermore, I examine intraspecific patterns of niche use according to sex, season, and reproductive stage in these two lemurs that differ in terms of energetic investment in reproduction. Lemurs as a group provide a special opportunity to test hypotheses concerning sex differences in niche use. Due to their body size monomorphism and seasonal, synchronous pattern of breeding, it is possible to directly evaluate whether sex differences in diet reflect high energetic investment in reproduction by females. Results confirm the hypothesis that intraspecific variation in niche use (e.g., sex differences, seasonal differences) would be more pronounced in V. v. rubra than in E. f. albifrons, due in large measure to the former's relatively high energetic investment in reproduction: 1a) Dietary sex differences in V. v. rubra are most pronounced during costly reproductive stages and involve acquisition of low-fiber, high-protein plant foods. Females of both species consume more seasonally available low-fiber protein (young leaves, flowers) relative to conspecific males during the hot dry season, but only in V. v. rubra females is this pattern also evident during gestation and lactation. 1b) The diets of female V. v. rubra and female E. f. albifrons are more similar to each other than are the diets of conspecific males and females in the case of V. v. rubra. This is not uniformly the case for female E. f. albifrons. This finding confirms a hypothesis put forward in Vasey ([2000] Am J Phys Anthropol 112:411-431) that energetic requirements of reproductive females drive niche separation more than do the energetic requirements of males. 1c) Both species synchronize most or all of lactation with seasonal food abundance and diversity. E. f. albifrons shows a more protracted period of synchrony, and this may contribute to its wide biogeographic distribution in Madagascar. 2) Sex differences and seasonal differences in microhabitat use reflect intraspecific patterns of thermoregulation, predator avoidance, and in the case of V. v. rubra, reproduction. One important factor selecting for body size monomorphism in lemurs appears to be the tight synchrony between lactation and periods of food abundance afforded by annual, seasonal breeding.

Shape of the Lateral Mandibular Outline in Lemuridae: A Quantitative Analysis of Variability Using Elliptical Fourier Analysis

“…1, 2). Long condyles are associated with frugivory [Bouvier, 1986;Smith et al, 1983], and so all the features we have noted above as distinguishing the mandibular profile of Eulemur, Lemur and Varecia may reflect a reduced masticatory apparatus in response to a diet consisting of fruits, leaves, flowers and buds [Petter et al, 1977;Tattersall and Sussman, 1998;Vasey, 2002;Yamashita, 2002].…”

Cathemerality in the Mayotte Brown Lemur (Eulemur fulvus) :Seasonality and Food Quality

“…The fi rst observations of cathemerality in E. f. fulvus in Mayotte were documented by Tattersall [1977] in the centre of the island, in the rainforest habitat at Mavingoni. In Mayotte, as is the case for fi eld sites in Madagascar, brown lemurs are opportunistic frugivore-folivores [Tattersall, 1977;Overdorff, 1992Overdorff, , 1993Vasey, 2000Vasey, , 2002Tarnaud, 2004a].…”

The development of sex differences in ring-tailed lemur feeding ecology

“…However, sex differences in multiple aspects of feeding are not only confined to species with large groups and strong female dominance but are also found in species that live in small groups where female dominance is low or absent (Overdorff 1991). Sex differences in dietary composition are present both in lemur species where males and females dedicate equal proportions of time to feeding and foraging (Richard 1978;Hemingway 1999); this study) and in those where sex differences in feeding time are present throughout the year (Overdorff 1996;Hemingway 1999;Grassi 2002;Vasey 2002). Even when there is an absence of sex and age differences in the consumption of broad food categories, ring-tailed lemurs showed low levels of dietary overlap within a group and significant differences in dietary diversity.…”

“…The low year-round dietary overlap and sex differences in dietary diversity that develop early in life and continue through adulthood indicate that some level of resource partitioning is present outside of reproductive activity. Like other primate females (Gautier-Hion 1980;Ganzhorn 1989a;Rose 1994;Vasey 2002;McCabe and Fedigan 2007;Yamashita 2008;Ganzhorn et al 2009), lactating ring-tailed lemurs shifted their dietary emphasis and fed more on young leaves and ripe fruit than did males and nonreproductive females. Female ring-tailed lemurs gestate during the period of lowest food availability, lactate during increasing food abundance, and wean their infants in the period of maximum food availability (Sauther 1991).…”

“…Reproductive costs may be more predictive of sex differences in feeding, particularly during lactation when these costs are greatest (CluttonBrock et al 1989;Altmann and Samuels 1992;Steudel 2000). These costs can structure much of the variation in dietary composition both within and among species, even to the extent that in some sympatric primate species, lactating females have diets more similar to each other than to male group members (Gautier-Hion 1980;Hemingway 1999;Vasey 2002). Pregnant and lactating females often need higher nutrient and energy intake to compensate for the increased metabolic costs associated with reproduction (Trivers 1972;Tilden and Oftedal 1997).…”