Anthropogenic effects on body size and growth in lab‐reared and free‐ranging Macaca mulatta. Issue 3 (7th March 2022)

• Record Type: Journal Article
• Authors: Francis, George; Eller, Andrea R.
• Is Part Of: American journal of primatology. Volume 84:Issue 3(2022)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2022-03-07
• Subjects: captive environments -- macaques -- maturity patterns -- postcranial -- skeletal variation; Primates -- Periodicals; Primates -- Périodiques; 599.8
• DOI: 10.1002/ajp.23368
• Languages: English
• ISSNs: 0275-2565

Abstract

Abstract: The impact of anthropogenic pressures upon primates is increasingly prevalent, and yet the phenotypic aspects of these impacts remain understudied. Captive environments can pose unique pressures based on factors like physical activity levels and caloric availability; thus, maturation patterns should vary under differing captive conditions. Here, we evaluate the development and growth of two Macaca mulatta populations ( N = 510) with known chronological ages between 9 months and 16 years, under different levels of captive management, to assess the impact of varying anthropogenic environments on primates. To track growth, we scored 13 epiphyseal fusion locales across long bones in a skeletal sample of lab‐reared M. mulatta ( n = 111), including the right tibia, femur, humerus, ulna, and radius. We employed a three‐tier scoring system, consisting of "0" (unfused to diaphysis), "1" (fusing), and "2" (fused). To record body size, we collected five linear measures of these long bones, from the proximal and distal ends, and total lengths. Means and standard deviations were generated to compare samples; t ‐tests were used to determine significant differences between means. These values were compared to available data on the free‐ranging, provisioned M. mulatta population of Cayo Santiago. The free‐ranging monkeys ( n = 274) were found to exhibit larger linear skeletal lengths ( p < 0.05) than lab‐reared specimens. Generally, the free‐ranging macaques reached fusion at earlier chronological ages and exhibited an extended duration of the fusing growth stage. These observations may reflect the protein‐rich diet provided to free‐ranging monkeys and conversely, restricted movement and relaxed natural selection experienced by lab‐reared monkeys. Abstract : This illustration depicts the hypothetical growth rate of a long bone over time, where the origin point is birth. The light red arrow indicates the complete time a long bone spends in growth until an epiphysis is fully fused to the diaphysis. The dark red arrow indicates the time this stage of growth is observable in a skeletal collection: from an epiphysis beginning to close in the youngest specimen in a population (left black dotted arrow) to the oldest specimen (right black dotted arrow). This final stage of bony growth was found to be extended among free‐ranging captive macaques, but not among lab‐reared populations. Research Highlights: Free‐ranging macaques have larger body sizes than their lab‐reared counterparts. Free‐ranging macaques exhibited an extended growth duration. Anthropogenic environments have the potential to influence the growth and development axiom within rhesus macaques and mirror trends documented in postindustrial humans.