The 84th Annual Meeting of the American Association of Physical Anthropologists (2015)

Offspring of Primiparous Mothers Do Not Experience Higher Mortality or Poorer Growth: Revisiting the Conventional Wisdom with Archival Records of Rhesus Macaques (Macaca mulatta)


1Department of Ecology, Duke University, 2Department of Human Evolutionary Anthropology, Harvard University, 3Department of Evolutionary Anthropology, University of California - Davis, 4Department of Electrical Engineering, Stanford University

March 26, 2015 , Archview Ballroom Add to calendar

Female mammals may begin to reproduce before achieving somatic maturity and therefore face tradeoffs between allocating energy to reproduction or their own continued development. Constraints on primiparous females are associated with greater reproductive failure, and first-born infants often have slower growth and higher mortality and morbidity than infants born to multiparous females. Effects of early life investment may persist even after weaning when juveniles are no longer dependent on maternal care and mother’s milk. We investigated the long-term consequences of differential maternal investment for both first-born and later-born offspring in a large sample of Macaca mulatta assigned to the outdoor breeding colony at the California National Primate Research Centre (N=2724). A joint model for growth and mortality over the first three years of life allowed us to explicitly connect growth rates to the likelihood of survival. As expected, males are born heavier and grow faster than females. However, contrary to expectations, later-born males face substantially lower survival probability during their first three years, whereas first-born males survive at higher rates similar to both first-born and later-born females. Compensating effects of physiological and behavioral adaptations in first-born offspring and their mothers, as well as the novel ecology of the captive environment, may explain these findings. Whatever the underlying causes, our results encourage us to consider how offspring calibrate and organize themselves in response to maternal investment strategies.

This research supported by NSF GRF-1106401 to CN, NSF BCS-0921978 and BCS-0525025 to KH.