The Challenge Hypothesis: Fecal Cortisol Levels in Male Red-Bellied Lemurs During the Reproductive Season

Abstract

In red-bellied lemurs (Eulemur rubriventer), a pair-bonded, monogamous species with paternal care, male fecal cortisol levels fluctuate over the reproductive season. The Challenge Hypothesis suggests a relationship between mating and infant care systems and hormone levels. During mating, fecal cortisol levels should be low due to little male-male mate competition. During gestation, males and females should have correlated hormonal responses if males prepare for infant care during their mate's pregnancy. Throughout infant growth, male fecal cortisol levels should elevate because paternal care is present. Red-bellied lemur male fecal cortisol levels were compared across reproductive seasons, and with their mate's fecal cortisol levels. Fecal cortisol levels were low during the mating season, higher during gestation, and highest around birth. During gestation, fecal cortisol levels were lower in males than females, and male fecal cortisol levels elevated about one to two weeks after their mate's. These results support predictions based on the Challenge Hypothesis, and suggest a paternal hormonal profile in this species.