This study quantifies changes in postural and locomotor behavior as well as habitat use across the life span of free-ranging rhesus macaques (Macaca mulatta) in the Cayo Santiago colony in Puerto Rico. It focuses on developmentally related changes from birth to adulthood, and complements an earlier study by Turnquist and Wells ([1994] J Hum Evol 26:487-499) on the early postnatal ontogeny of the musculoskeletal system of the same colony. A total of 6,551 locomotor and postural events was analyzed. Selection and use of substrate correlated well with age. The more sedentary adult and dependent infant select safe, wide, horizontal arboreal settings in contrast to the older Infant IIs and Juveniles, who are learning locomotor and postural skills through independent chase and play. Infant macaques, when independent, often employ a low center of gravity and widely abducted limbs in order to broaden their contact with the base of support. This study shows that the previously reported ontogenetic changes in morphology are closely paralleled by changes in postural and locomotor behavior, and these in turn are correlated to changes in habitat use, particularly during the formative years.

The dynamic role of the prehensile tail of atelines during locomotion is poorly understood. While some have viewed the tail of Ateles simply as a safety mechanism, others have suggested that the prehensile tail plays an active role by adjusting pendulum length or controlling lateral sway during bimanual suspensory locomotion. This study examines the bony and muscular anatomy of the prehensile tail as well as the kinematics of tail use during tail-assisted brachiation in two primates, Ateles and Lagothrix. These two platyrrhines differ in anatomy and in the frequency and kinematics of suspensory locomotion. Lagothrix is stockier, has shorter forelimbs, and spends more time traveling quadrupedally and less time using bimanual suspensory locomotion than does Ateles. In addition, previous studies showed that Ateles exhibits greater hyperextension of the tail, uses its tail to grip only on alternate handholds, and has a larger abductor caudae medialis muscle compared to Lagothrix. In order to investigate the relationship between anatomy and behavior concerning the prehensile tail, osteological data and kinematic data were collected for Ateles fusciceps and Lagothrix lagothricha. The results demonstrate that Ateles has more numerous and smaller caudal elements, particularly in the proximal tail region. In addition, transverse processes are relatively wider, and sacro-caudal articulation is more acute in Ateles compared to Lagothrix. These differences reflect the larger abductor muscle mass and greater hyperextension in Ateles. In addition, Ateles shows fewer side-to-side movements during tail-assisted brachiation than does Lagothrix. These data support the notion that the prehensile tail represents a critical dynamic element in the tail-assisted brachiation of Ateles, and may be useful in developing inferences concerning behavior in fossil primates.

No abstract

This cross-sectional study investigates metabolic bone disease and the relationship between age and bone mineral density (BMD) in males and females of a large, well-documented skeletal population of free-ranging rhesus monkeys (Macaca mulatta), from the Caribbean Primate Research Center Museum collection from Cayo Santiago, Puerto Rico. The sample consists of 254 individuals aged 1.0-20+ years. The data consist of measurements of bone mineral content and bone mineral density, obtained from dual-energy X-ray absorptiometry (DEXA), of the last lumbar vertebra from each monkey. The pattern of BMD differs between male and female rhesus macaques. Females exhibit an initial increase in BMD with age, with peak bone density occurring around age 9.5 years, and remaining constant until 17.2 years, after which there is a steady decline in BMD. Males acquire bone mass at a faster rate, and attain a higher peak BMD at an earlier age than do females, at around 7 years of age, and BMD remains relatively constant between ages 7-18.5 years. After age 7 there is no apparent effect of age on BMD in the males of this sample; males older than 18.5 years were excluded due to the presence of vertebral osteophytosis, which interferes with DEXA. The combined frequency of osteopenia and osteoporosis in this population is 12.4%. BMD values of monkeys with vertebral wedge fractures are generally higher than those of virtually all of the nonfractured osteopenic/osteoporotic individuals, thus supporting the view that BMD as measured by DEXA is a useful but imperfect predictor of fracture risk, and that low BMD may not always precede fractures in vertebral bones. Other factors such as bone quality (i.e., trabecular connectivity) should also be considered. The skeletal integrity of a vertebra may be compromised by the loss of key trabeculae, resulting in structural failure, but the spine may still show a BMD value within normal limits, or within the range of osteopenia.

Pendular motion during brachiation of captive Lagothrix lagothricha lugens and Ateles fusciceps robustus was analyzed to demonstrate similarities, and differences, between these two closely related large bodied atelines. This is the first captive study of the kinematics of brachiation in Lagothrix. Videorecordings of one adult male of each species were made in a specially designed cage constructed at the DuMond Conservancy/Monkey Jungle, Miami, FL. Java software (Jandel Scientific Inc., San Rafael, CA) was used for frame-by-frame kinematic analysis of individual strides/steps. Results demonstrate that the sequence of hand and tail contacts differ significantly between the two species with Lagothrix using a new tail hold with every hand hold, while Ateles generally utilizes a new tail hold with only every other hand hold. Stride length and stride frequency, even after adjusting for limb length, also differ significantly between the two species. Lagothrix brachiation utilizes short, choppy strides with quick hand holds, while Ateles uses long, fluid strides with longer hand holds. During brachiation not only is Lagothrix's body significantly less horizontal than that of Ateles but also, within Ateles, there are significant differences between steps depending on tail use. Because of the unique nature of tail use in Ateles, many aspects of body positioning in Lagothrix more closely resemble Ateles steps without a simultaneous tail hold rather than those with one. Overall pendulum length in Lagothrix is shorter than in Ateles. Tail use in Ateles has a significant effect on maximum pendulum length during a step. Although neither species achieves the extreme pendulum effect and long period of free-flight of hylobatids in fast ricochetal brachiation, in captivity both consistently demonstrate effective brachiation with brief periods of free-flight and pendular motion. Morphological similarities between ateline brachiators and hylobatids are fewer and less pronounced in Lagothrix than in Ateles. This study demonstrates that Lagothrix brachiation is also less hylobatid-like than that of Ateles.

No abstract

This article describes the dental eruption patterns, dentition, and dental wear, including tooth loss and breakage, of the free-ranging population of rhesus monkeys (Macaca mulatta) on Cayo Santiago (CS), Puerto Rico, ranging from 24 hr to 25 years old. Of the 694 monkeys on the island in the year 1985, 688 (99.1%; 366 males, 322 females) were captured and the dentition of 685 subjects (98.7% of the total population; 366 males, 319 females) was examined. Animals ranged in age from less than 24 hr to 331 months (27.58 years), encompassing the entire life span of the CS macaques. Results demonstrated that the first deciduous teeth appeared as early as the third day of life and that the sequence of dental eruption was comparable to the pattern observed in laboratory rhesus. However, there were slight differences in the age of eruption of individual teeth. For example, the canines and third molars erupted about a year later in the CS macaques compared to some laboratory rhesus. Overall, CS rhesus had good oral health and dental condition although tooth wear, loss, and breakage were common in aged animals, especially in males. This report, combined with earlier studies on morphological characteristics and skeletal remains of the CS macaques, provides the basis for further studies on the biology, genetics, life history, and effects of the environment on rhesus monkeys.

One contribution of 17 to a discussion meeting issue 'Major transitions in human evolution'. Homo erectus was the first hominin to exhibit extensive range expansion. This extraordinary departure from Africa, especially into more temperate climates of Eurasia, has been variously related to technological, energetic and foraging shifts. The temporal and regional anatomical variation in H. erectus suggests that a high level of developmental plasticity, a key factor in the ability of H. sapiens to occupy a variety of habitats, may also have been present in H. erectus. Developmental plasticity, the ability to modify development in response to environmental conditions, results in differences in size, shape and dimorphism across populations that relate in part to levels of resource sufficiency and extrinsic mortality. These differences predict not only regional variations but also overall smaller adult sizes and lower levels of dimorphism in instances of resource scarcity and high predator load. We consider the metric variation in 35 human and non-human primate 'populations' from known environmental contexts and 14 time-and space-restricted paleodemes of H. erectus and other fossil Homo. Human and non-human primates exhibit more similar patterns of variation than expected, with plasticity evident, but in differing patterns by sex across populations. The fossil samples show less evidence of variation than expected, although H. erectus varies more than Neandertals.This article is part of the themed issue 'Major transitions in human evolution'.