Free-ranging Cayo Santiago rhesus monkeys (Macaca mulatta): I. Body size, proportion, and allometry.

This paper presents comprehensive baseline data on body size and proportion of 661 (315 male, 346 female) free-ranging Cayo Santiago rhesus monkeys (Macaca mulatta) ranging in age from 24 hours to 25 years. All animals were born and raised in the free-ranging colony on Cayo Santiago, and exact ages were known for all. Tabular data from this cross-sectional study are provided to enable comparisons with data from laboratory, wild, and other captive populations of rhesus monkeys, as well as with other species. Despite the extensive literature on rhesus monkey behavior and biology, to date published accounts of its morphometrics have been limited to only a few measurements from animals of unknown age, small sample sizes, or caged colonies. Results of this study showed a distinct intraspecific pattern for body proportions throughout the life cycle. Relative linear increases in overall body proportions of maturing animals appeared to be from greatest to least in the trunk, hindlimb, and forelimb, respectively. Within the limbs, allometric scaling appeared to be fastest in the proximal segment and slowest in the distal segment. Males and females differed in the duration of growth, and gender dimorphism was associated primarily with differences in size rather than proportion. Although the primary purpose of this paper is to present numerical data on the Cayo Santiago colony, the results are compared with previous studies of both laboratory and free-ranging rhesus monkeys.