A Ten-Year Summary of Reproductive Data for Free-Ranging Macaca mulatta

Analyses were made of population statistics and reproduction parameters covering a ten-year period at the free-ranging rhesus monkey colony at La Parguera, Puerto Rico. The mean annual rate of population increase was 13 %. Young females gave birth to their first infant at four years of age on the average. More than 60 % of the births occurred during May and June with an annual median birth date (1966–1972) ranging from May 30 to June 8. Females not having an infant one year gave birth earlier than the median date the next year, while a large percentage of females giving birth late in a birth season did not produce an infant the next year. Between 40 and 50 % of the infants born first or second to a female did not survive their first year, but by the fourth infant born to the same female only 9 % died during the first 12 months. The social rank of adult females affected several parameters: infants born to high-ranking females had a higher rate of survival than young of low-ranking females; a larger percentage of high-ranking females gave birth each year than low-ranking females and daughters of high-ranking females produced their first infants at an earlier age than daughters of low-ranking females. Both males and females survived in equal proportions until four years of age, after which males had higher mortality rates and the death rate for females remained very low and constant.