Ecology of reproduction in Sanje mangabeys (Cercocebus sanjei): dietary strategies and energetic condition during a high fruit period.

The ability to increase energy storage when food is abundant for later use during late gestation and early lactation is often considered the primary benefit of the capital breeding strategy (clustering conceptions during high food periods, HFP) that promotes reproductive success among females living in unpredictable environments. Capital breeding, however, may also enable preconceptive females to increase hormone production for ovulation, which has been linked to energetic condition in capital breeders, and/or allow females entering the subsequent HFP to increase their energetic condition in order to continue nursing unweaned infants. Here, we investigate whether capital breeding provides these additional benefits in 16 female Sanje mangabeys (Cercocebus sanjei) and determine the dietary strategies used to increase energetic condition (measured by urinary C-peptide: UCP) during the HFP. Fecal estradiol (fE2 ) and UCP were negatively correlated with number of cycles before conception (r = -0.591, r = -0.646, P < 0.01) and were highest in conceptive cycles. Both peri-conceptive (preconception and early gestation) and non-peri-conceptive (lactation) females increased energetic condition over the HFP (r = 0.612, r = 0.583, P < 0.001) by increasing dietary fat (r = 0.619, r = 0.703, P < 0.001) and, for non-peri-conceptive females, protein (r = 0.437, P < 0.001). Feeding intake rate (FIR) and time spent foraging and feeding did not change over the HFP; however, non-peri-conceptive females exhibited a faster FIR compared to peri-conceptive females (t = -2.324, P < 0.05), consuming almost twice as much food per unit time. The results of this study confirm that Sanje mangabeys benefit in multiple phases of the reproductive cycle by using capital breeding, which may explain how this strategy promotes female reproductive success.