Abstract # 21:

Scheduled for Saturday, September 17, 2011 11:30 AM-11:45 AM: Session 5 (Meeting Room 408) Oral Presentation


M. S. Wechsler1 and K. Hinde1,2
1University of California Davis, Brain, Mind, & Behavior Unit, California National Primate Research Center, One Shields Ave, Davis, CA 95616, USA, 2Department of Human Evolutionary Biology, Harvard University

Primiparous mothers face tradeoffs between investing in reproduction and their own continued growth. Among rhesus macaques, daughters born to primiparous mothers receive less and lower quality milk, and are significantly smaller than are daughters of multiparous mothers. The long-term consequences for first-born daughters, however, are not well understood. We investigated reproductive outcomes among Macaca mulatta females as a function of their birth order, a proxy for the maternal investment they received during infancy. In our sample, 47/196 females were firstborns (born to primiparous mothers) and 149/196 were later-borns (born to multiparous mothers). We found that firstborn females, who presumably received less maternal investment, initiated reproduction at the same age and mass as later-born females (4.11±0.1 years vs. 3.99±0.04 and 6.9±0.2 kg vs. 7.1±0.1, both NS). On their first parity, however, firstborn females produced significantly less milk during peak lactation than did later-born females (10.13±1.2 grams vs. 13.8±1.0, p<0.05). This difference, however, disappears with increasing parity and repeated functional development of the mammary gland; among multiparous mothers, firstborns and later-borns produced identical milk yield (16.6±1.4 grams vs. 16.8±0.7, NS). These results suggest that first-born daughters in captivity, with ample access to food resources, can “catch-up” in growth and fertility with later-born females, but that morphological development of the mammary gland is somewhat sensitive to conditions during early development. This research supported by NSF BCS-0921978 and BCS-0525025