Hand preference by black-and-white snub-nosed monkeys (Rhinopithecus bieti) in captivity: influence of tasks and sexes.

Task complexity (Fagot & Vauclair 1991), bimanual complementary role differentiation (Uomini 2009), and the obligate use of a particular hemisphere (Rogers, 2009) have been proposed to explain why hand preferences in non-human primates are often influenced by tasks. We examined how tasks (reaching, carrying, extractive foraging, and object manipulation) and gender influenced hand preference in 11 adult black-and-white snub-nosed monkeys (Rhinopithecus bieti) out of a total of 13 known adult captive individuals of this species. A logistic regression was used to analyse 2556 bouts of binary left- vs right-hand use data. The explanatory variables are tasks, gender, and the interaction of tasks and gender. Hand preference is influenced by the task, in that subjects used the right hand significantly more often for extractive foraging and object manipulation than for reaching and carrying. We also found a significant interaction of sex and task: males used the left hand significantly more often than females for reaching and carrying, respectively, but not for extractive foraging or object manipulation. This is the first study on hand preference in R. bieti. As predicted, the hand preference in R. bieti is not a fixed property of the species or sexes but depends on the task.

Seasonal changes in body weight of Macaca thibetana at Mt. Emei, China.

This 1991-1992 study was designed to expand previous research on body weight (BW) in Tibetan macaques (Macaca thibetana) at Mt. Emei. Data on BW were collected in late autumn (LA) and late winter (LW) in groups ranging above 1,200 m. Over the winter, the BW fell significantly from a mean of 16.8 to 11.4 kg in females and from 19.5 to 17.0 kg in males. The previously reported BW means of 12.8 kg for females and 18.3 kg for males, measured in late spring, are near the center of the annual BW range for this species. In addition, with the sharper decline of female BW (-32% vs. -13% seen in males), the sexual dimorphism (M/F) in BW increased from 1.16 in LA to 1.49 in LW. This finding may be related to differential parental investment by two sexes. © 1994 Wiley-Liss, Inc.

Macaca thibetana at Mt. Emei, China: III. Group composition.

Data on group composition at the end of the 1986 birth season were collected from six groups of Macaca thibetana. All adult males, the members of group A, and some conspicuous animals were recognized individually. Fourhundred survey sessions were completed. The mean group size was 38.3 (SD = 13.8, range: 28-65); the number of adult females was the best correlate of total group size. The mean adult sex ratio (F:M) across groups was 3:1 (SD = 1.9, range: 1.5-6.5:1), which significantly deviated from 1:1. Sex ratios (F:M) in newborns, juveniles, and all members did not significantly deviate from 1. The ratio of immature animals to adults was 1.5 to 1 (average of groups); that is, 60% of the population was composed of immature animals, and the population was growing.

Macaca thibetana at Mt. Emei, China: II. Birth seasonality.

Birth censuses were conducted every 2 or 3 days for each of six groups of Macaca thibetana along trails at Mt. Emei in southwest China from March 7 to June 15, 1986. Based on direct observations and the timetable of forehead hair growth and behavior, each of 32 infants could be placed in one of sixteen 14-day periods of the 1986 birth season. The mean estimated birth date was March 27 (SD = 39 days); the median estimated birth date was March 14. Sex ratios in newborns and yearlings did not deviate significantly from 1:1. Seasonal birth timing was correlated with the altitude of the range (r = -0.84, P < .05); that is, infants were born earlier in the season at higher altitudes.

Macaca thibetana at Mt. Emei, China: I. A cross-sectional study of growth and development.

Six free-ranging groups of Macaca thibetana were studied at Mt. Emei, in southwest China. Patterns of growth and development observed during the study are described for this species for the first time. Data were collected mainly during the birth season of 1986. Food handouts made possible the measurement of body weight and sitting height. Changes in fur color and growth of forehead hair were noted. Dark hair appeared on the broad white forehead of infants at the end of the third month. A triangular patch formed about 30 days later, and full cover developed within 4.5 to 5 months. For the first 1 or 2 weeks, the fur was blackish; it then became yellow, and by the age of 3.5-4.5 months, it was brown or blackish, i.e., adult color. Growth data on body weight and sitting height for different age-sex classes were collected. For adult males, body weight was 18 kg, sitting height (SH) 55 cm, and ponderal index 33. For adult female, body weight was 13 kg, sitting height 47 cm, and ponderal index 27. Females were considered to be adult at age 5 years.

Excrement distribution and habitat use in Rhinopithecus bieti in winter.

Winter ranging patterns of Rhinopithecus bieti were determined using feces as the ranging trace. The appearance of the feces was unique in the study habitat. The sampled habitats were a well-forested area and a partly altered one. Analyses of excrement distribution showed: (1) monkeys tended to use the upper part of the forest belt, ranging between 3,900 and 4,100 m above sea level; (2) monkeys came to the ground and used the partly altered habitat, where only some forest remained; (3) the structure of resources had little influence on determining the ranging elevation; and (4) the animals spent more time in the local valley than on the local ridge, probably using the former as a sleeping site.

Sleeping sites of Rhinopithecus bieti at Mt. Fuhe, Yunnan.

Data on sleeping site selection were collected for a group of black-and-white snub-nosed monkeys (Rhinopithecus bieti; around 80) at Mt. Fuhe, Yunnan, China (99 degrees 20'E, 26 degrees 25'N, about 3,000 m asl) from November 2000 to January 2002. At the site mainly three vegetation types were present in an elevation-ascending order: deciduous broad leaf forest, mixed coniferous and broad leaf forest, and dark coniferous forest. In addition, bamboo forest presented in areas burned in 1958. Sleeping sites (n =10) were located in the coniferous forest, where trees were the tallest, bottommost branches were the highest, the diameter of crowns was the second largest, and the gradient of the ground was the steepest. Monkeys usually kept quiet during entering and staying at a sleeping site. The site choice and the quietness may be tactics to avoid potential predators. In the coniferous forest, however, monkeys did not sleep in the valley bottom where trees were the largest, but frequently slept in the middle of the slope towards the east/southeast, in the shadow of ridges in three other directions, to avoid strong wind and to access sunshine; in winter-spring, they ranged in a more southern and lower area than in summer-autumn. These may be behavioral strategies to minimize energy stress in the cold habitat. Monkeys often slept in the same sleeping site on consecutive nights, which reflected a reduced pressure of predation probably due to either the effectiveness of anti-predation through sleeping site selection, or the population decline of predators with increasing human activities in the habitat. The group's behavioral responses to interactive and sometimes conflicting traits of the habitat are site-specific and conform to expectations for a temperate zone primate.