Study On The Position Behavior Pattern Of Rhinopithecus Roxellana

Positional adaptations reflect important evolutionary distinctions that primates how to exploit their environment, obtain access to food resources, and avoid predators as well as in the energetic costs of travel. Body mass plays an important role in primate positional behavior and in sexually dimorphic arboreal primate species may influence how immature and adult individuals travel through the forest canopy and access food resources. In this study, we examined age- and sex- based patterns of positional behavior and substrate utilization in wild golden snub-nosed monkeys (Rhinopithecus roxellana), an endangered species of Asian colobine.This study was conducted from November 2011 to January 2013. We choosed 34 individuals as focus animals and quantitative information on positional behavior were collected using focal-animal instantaneous sampling at one-minute intervals.20,131 behavioral records were obtained. Our results indicated that among all age and sex classes, sitting was the most common feeding and resting posture and during travel, quadrupedal walking was the dominant locomotor behavior. Despite the fact that adult male R. roxellana are reported to exhibit a body mass nearly two times that of adult females, we found no significant sex differences in the positional repertoire during feeding and traveling. In addition, we found that while infants and juveniles used similar postural and locomotor behaviors as their adult counterparts, younger golden snub-nosed monkeys more frequently engaged in risky or escape-oriented behaviors such as climbing, running, leaping, and forelimb suspension. With increasing age, the use of quadrupedal walking and dropping (downward in air displacement of body mass that does not require hindlimb propulsion) increased and the use of leaping, suspensory postures, and bridging decreased. Finally, given differences in the positional repertoire of adult and immature golden snub-nosed monkeys, we argue that studies of ontogenetic patterns of positional behavior should emphasize what it takes to survive at each life stage rather than what it takes to match an adult repertoire.Our results suggest that R. roxellana spent 19.16% time on the ground and tend to be semi-terrestrial. The time spent on the ground by R. roxellana increased with their age increasing. Adults spent significantly more time in the Lower Canopy than all other age categories. While Infants and Juveniles stayed more often in the Upper canopy. Though R. roxellana preferred to use Small and Medium substrates, Adults and Subadults spent more time on Large substrates than Infants and Juveniles. Adults and Subadults spent significantly more time feeding on the Ground than juveniles and Infants. Males were observed feeding on the Ground significantly more often than females. In contrast, Infants and Juveniles were observed to feed in the Upper canopy significantly more often than adults and Subadults. Infants and Juveniles also were observed on Terminal substrates significantly more often than Subadults and Adults. Juveniles and Infants spent more time traveling in the Upper Canopy than Adults. Infants travelled on Terminal substrates significantly more often than all other age categories. Adults travelled on Medium and Large substrates more often than Infants. Juveniles travelled on Small and Medium substrates significantly more often than Subadults but not adults. Subadults were observed to travel on Large substrates more often than Adults. Conversely, Adults were observed to travel on Small substrates significantly more often than Subadults.We recorded 11,667 locomotor behaviors using continuous sampling method, among which,11,026 bouts were under normal status and 641 were under crisis status. We measured the single gait distances of 502 and 468 leapt behavior of adult male and adult femal R. roxellana respectively.We found that the locomotor repertoire of R.roxellana was more diversified on the tree than on the ground under normal status. Though R. roxellana often use slow quadrupedalism walking in their daily activities whatever traveling on the tree or on the ground, they seem to avoid walking and prefer to leaping、running and climbing.The mean leapt distance of R. roxellana is 136.199±50.317 cm. The mean leapt distance under crisis status is larger than that under common status.The leapt distance is also infleuned by direction, support size and obliquity. Results showed leap behavior usually happened on the vertical or inclined branches. The single gait distance across and downward were longer than upward. The mean leapt distance of adult males is longer than adult females. Though they all avoid using Terminal substrates, males prefer to using Large supports, while females prefer to using Small supports.We measured the body structures of male and female R. roxellana. Results indicated that body length, body width, for-and hind-limb of adult males are all longer than adult females, but their limb proportions were similar. We considered the sex differences on leap behavior are more related to the limb length and muscle strength than limb proportions.