Positional Behavior and Support Use of the Tonkin Snub-Nosed Monkeys (Rhinopithecus avunculus) in Khau Ca Forest, Ha Giang Province, Vietnam

摘要

Studies of the positional behavior of wild primates are important for understanding relationships between ecology, behavior and morphology. The aim of this study was to examine the effects of body size, dimorphism, ontogeny and seasonal changes on positional behavior and support use of the Tonkin snub-nosed monkey (Rhinopithecus avunculus). From January 2009 to December 2010, I collected videography-based data on the positional behavior and support use via bout sampling method of R. avunculus in Khau Ca Forest, Ha Giang Province, Vietnam. I also studied the forest structure and phenology of the habitats of R. avunculus in Khau Ca Forest. Using G-tests (Row x Column statistical comparisons), I tested for significant differences in postural and locomotor profiles for associated maintenance activities, sex- and age-based differences, and seasonal changes for the Tonkin snub-nosed monkeys.First, I documented the positional repertoire of adult male R. avunculus to include nine locomotor modes (19 submodes) and six postural modes (16 submodes). Quadrupedalism was the most frequent locomotion, followed by leap, climb, drop, arm-swing, and other locomotion. Sitting was the most frequent posture, followed by stand, lie, cling and other postures.Second, I tested sex-based differences in positional behavior and support use of R. avunculus. The results showed that there were differences between adult males and females in positional behavior and support use, but these differences did not consistently follow the predictions based on body size.Third, I found there were significant age-based differences in positional behavior and support use of R. avunculus during maintenance activities. Larger-bodied adults climbed more frequently, and leapt less frequently than smaller-bodied juveniles and infants during travel. The frequency of sitting increased with age while resting and feeding. Larger-bodied adults tended to use larger supports and more flexible supports than smaller-bodied juveniles and infants.Finally, the data indicated that there were significant differences between dry/cold and wet/warm seasons in positional behavior and support use of R. avunculus. Seasonal changes in positional behavior and support use of R. avunculus might be associated with the shift of diet, foraging/feeding behavior, and ambient temperatures by seasons.