Infant Development and Maternal Care in Wild Verreaux’s Sifaka (Propithecus verreauxi)

Abstract

Investigating factors influencing infant physical and social development is important to elucidate primate adaptations and life history evolution. Infant sifakas exhibit a puzzling mismatch between dental precocity and relatively slow postnatal growth, but only anecdotal reports of infant development are available for a comparative appraisal of their early life history and maturation. We therefore collected behavioral data on mother–infant dyads of 16 infant Verreaux’s sifakas (Propithecus verreauxi) from 3 birth cohorts in Kirindy Forest to assess how the infant’s age, sex, mother’s age, and environmental variation influence the infant’s development until weaning. We found that somatic growth rates differed between the sexes, with females growing faster than males. Infants began ingesting solid food as early as 3 weeks of age, which is extremely early for a primate of this size and much earlier than in Lemuridae. Social behavior emerged at a later age than motor skills. Despite pronounced variation in the timing and occurrence of various infant activities, none of them differed between the sexes, except that male infants were more engaged in grooming others than females. Infant sifakas did not develop faster than other lemurs despite the extra available energy gained from ingesting solid food at an early age, but their mothers carry them for a relatively long period, perhaps because vertical clinging and leaping is a locomotor style that requires prolonged physical maturation. The adaptive significance of their dental precocity remains elusive, however. Thus, further studies are required to understand how developmental schedules have coevolved with ecological and anatomical factors.