1Human Evolutionary Biology, Harvard University, 2Brain, Mind, and Behavior Unit, California National Primate Research Center
Friday 3:15-3:30, Galleria North
Primiparous mothers often face tradeoffs between allocating energy to reproduction and their own continued growth. Among rhesus macaques, primiparous mothers particularly restrict investment in their daughters. We investigated the long-term consequences of reduced maternal investment, using birth order as a proxy measure, among a large sample of Macaca mulatta females assigned to the outdoor breeding colony at the California National Primate Research Center (N=219). Although first-born daughters initiated reproduction at the same age as their later-born counterparts (first birth at 4.06±0.09 years vs. 4.04±0.05, NS), they had significantly lower body mass (6.7±0.12 kg vs. 7.1±0.09, p=0.02). Additionally, on their first parity, first-born females produced significantly less milk at peak lactation than did later-born females (10.2±1.4 grams vs. 14.1±0.9, N=56, p=0.05). These differences, however, were not present between first-born and later-born multiparous females. Both body mass (8.97±0.3 and 9.39±0.2, N=163, NS) and milk yield at peak lactation (16.76±1.2 grams vs. 16.78±0.9 grams, NS) were the same for both groups. These data demonstrate that the consequences of reduced maternal investment in infancy persist following weaning and that first-born daughters, even with ample access to food resources in captivity, can not compensate during juvenile development or at the outset of their reproductive careers. Subsequent reproductive efforts however, likely precipitate physiological processes that facilitate eventual “catch-up” during maturity. These results from a captive population suggest that under natural ecological conditions the consequences of being a first-born daughter are of potentially greater magnitude and longer persistence.
This research supported by NSF BCS-0921978 and BCS-0525025 to KH and NIH RR019970 to J. Capitanio and RR000169 to the CNPRC.