Maternal Effort, Food Quality, and Cortisol Variation during Lactation in Propithecus Coquereli in Northwestern Madagascar

The duration and quality of the infant care mothers provide is paramount to investigating life history theory. Maternal care is the principal determinant of infant survival and future reproductive success. Lactation is the most energetically expensive activity for mammals, in turn causing lactating females to compensate for drastically greater energy requirements. Lemur reproduction occurs under strict seasonal parameters to cope with harsh climatic conditions. I evaluated maternal behavioral care-giving effort towards infants over 26 postnatal weeks in Coquerel's sifaka (Propithecus coquereli ) (n = 10 infants, n = 10 lactating females). Secondly, I evaluated the nutritional quality of foods consumed exclusively by lactating females (n = 10). Lastly, I examined stress responses across sex and reproductive classes in earlier (weeks 1--12) versus later lactation (weeks 13--24) (n = 0 lactating females, n = 19 adult males, n = 8 non-lactating adult females). I conducted fieldwork over two consecutive birth seasons (2010 and 2011) in Ankarafantsika National Park located in northwestern Madagascar. Earlier lactation occurs during the austral winter, and coincides with the seasonally driest time of the year. I quantified maternal care-giving by measuring infant transport position, carrier identity, and bodily contact. Nutritional food quality was measured by protein, fiber, energy (n = 123), and mineral content (n = 119). I quantified stress responses to determine how sex and reproductive classes respond to seasonal pressures and lactation by measuring cortisol variation in two lactation stages in lactating females (n = 180), adult males, (n = 133), and non-lactating adult females (n = 62). Infants were more altricial relative to other lemurs of similar body size. Allomaternal care was documented, although mothers were the primary infant transporters. Lactating females most frequently selected foods high in non-protein energy, and regularly selected foods high in available protein and fiber. Lactating females had lower cortisol relative to adult males that approached statistical significance, and significantly lower cortisol than non-lactating adult females. Adult males had significantly higher cortisol during the earlier lactation stage in comparison to the later stage. Understanding the behavioral, nutritional, and endocrinological responses of lactating females provides a comprehensive view of how maternal energetics, infant care, and infant development are dynamically performing during the most energetically constraining time of year in a stochastic environment.