Diet and activity budget of Rhinopithecus roxellana in the Qinling Mountains, China

We collected data on diet and daytime activity budget, and investigated the phenology of food trees and food abundance for a group of Rhinopithecus roxellana on the East Ridge of Yuhuangmiao in the Qinling Mountains from November 2001 to December 2003. We calculated the seasonal activity budget using data collected by scan sampling from 84 full-day observations (winter 16, spring 18, summer 28, autumn 22 days). During scan sampling we recorded behavioral states, and the food items and species consumed. The subjects consumed 84 plant species, including trees and shrubs of 29 families, and lichens. Food species varied seasonally. The overall diet of R. roxellana consisted of 29.4% fruit/seeds, 29.0% lichens, 24.0% leaves, 11.1% bark, 4.2% buds, 1.3% twigs and 1.0% unidentified items. Because the abundance of different food items varied seasonally, the monkeys had to shift their major food items seasonally. The annual activity budget of R. roxellana was 36.2% time spent resting, 35.8% feeding, 22.9% moving, and 5.1% other behavior. Seasonal changes in activity budget were observed. R. roxellana spent more time moving in autumn, when the quality of the food might be highest, and least time moving in winter when the food quality might be lowest. Thus, this type of monkey has a passive foraging strategy.

Leaf selection by two Bornean colobine monkeys in relation to plant chemistry and abundance

Focusing on the chemical basis of dietary selection while investigating the nutritional ecology of animals helps understand their feeding biology. It is also important to consider food abundance/biomass while studying the mechanism of animal food selection. We studied leaf selection in two Bornean folivorous primates in relation to plant chemistry and abundance: proboscis monkeys inhabiting a secondary riverine forest and red leaf monkeys inhabiting a primary forest. Both species tended to prefer leaves containing higher protein levels, although more abundant plant species were chosen within the preferred species, probably to maximise energy gain per unit time. However, the two species showed clear differences in their detailed feeding strategy. Red leaf monkeys strictly chose to consume young leaves to adapt to the poor nutritional environment of the primary forest, whereas proboscis monkeys were not highly selective because of the better quality of its common food in the riverine forest.

Seed dispersal by neotropical seed predators

From a plant's perspective, the difference between a seed predator and a seed disperser should be straightforward: attract animals that will disperse seeds and defend seeds from potential predators. Unlike pulp-eating frugivores, seed predators regularly encounter diverse plant protective mechanisms. The purpose of this paper is to examine feeding constraints, morphological adaptations, and the mechanical process of seed predation. While there is evidence that some seed predators cause severe losses to seed crops, there is also evidence that seed predators enhance seed dispersal and germination. We also examine four methods by which neotropical seed predators may contribute to dispersal. 1) Seed predators examined here ingested fruit when seeds were full-sized, but not yet mature (i.e., seeds of mature fruit may be avoided by seed predators and available for dispersal by other frugivores). 2) Sympatric seed predators may ingest seeds from different plants thus reducing overall predator load on any individual plant. 3) Seed predators that manipulate seeds (e.g., remove pericarp and seed coat) may enhance germination if the prepared seeds are dropped, discarded, or buried and not ingested. 4) Small seeds may miss mastication and swallowed intact with a food bolus. The last mechanism is the most likely to contribute to seed dispersal by the widest array of vertebrate seed predators, but primate seed predators may facilitate seed dispersal using all four mechanisms. Therefore, the traditional dichotomy of seed predator vs. seed disperser oversimplifies the interactions between seed predators and plants.

Seasonal variation of diet and food availability in a group of Sichuan snub-nosed monkeys in Shennongjia Nature Reserve, China

We studied the diet and food availability of a group of Sichuan snub-nosed monkeys for 14 months (July 2003 to September 2004, except for February) in the Shennongjia Nature Reserve, China. This species is primarily a lichen eater, with lichens (Usneaceae) accounting for 43.28% of feeding records (n=3,452). Other food types in the diet were young leaves (28.71%), fruits or seeds (14.57%), buds (5.36%), mature leaves (3.51%), herbs (2.09%), bark (1.36%), and flowers (1.13%). The monkeys used 23 plant species. Their diet showed a complicated seasonal variation: the monthly diet varied from primarily lichens in November-April, to a mixture of leaves and lichens in May-July, to a mixture of fruits or seeds and lichens in August-October (the latter depended on annual fruit and seed availability). The proportion of fruits or seeds in the diet was negatively correlated with that of lichens, which suggests that the monkeys prefer fruits or seeds to lichens when all of these items are available. The fruit or seed availability varied greatly between the two study years. The proportion of lichens, young leaves, flowers, and fruits or seeds in the diet was positively associated with their availability. The monkeys appeared to be selective feeders. They preferred 10 tree species for plant parts, and nine tree species for lichens. The selection index of tree species for lichens was positively related to lichen coverage per branch on tree species, demonstrating that the monkeys preferred tree species with abundant lichens, as well as dead trees for lichens. The results suggest that dead-tree harvesting in the reserve could significantly reduce the quality of habitat for these monkeys, and should therefore be prohibited. Connus controversa, Cerasus discadenia, Salix willichiana, and Malus halliana should be conserved as top priority species because the monkeys preferred them for both their vegetative parts and the lichens that grow on them.

Parasite prevalence and richness in sympatric colobines: effects of host density

Factors that influence proximity and the number and duration of contacts among individuals can influence parasite transmission among hosts, and thus parasite prevalence and species richness are expected to increase with increasing host density. To examine this prediction we took advantage of a unique situation. Following the clearing of a forest fragment that supported red colobus (Piliocolobus tephrosceles) and black-and-white colobus (Colobus guereza), the animals moved into a neighboring fragment that we had been monitoring for a number of years and for which we had described the primate parasite community. After the animals immigrated into the fragment, the colobus populations more than doubled and colobus density became almost twice that found in Kibale National Park, Uganda. Despite this increase in host density, the richness of the parasite community did not increase. However, in both colobus species the prevalence of Trichuris sp., the only commonly occurring gastrointestinal parasite, increased. Over the next 5 years the prevalence and intensity of infection of Trichuris sp. in red colobus declined and their population numbers slowly increased. In contrast, the prevalence and intensity of infection of Trichuris sp. increased in black-and-white colobus and remained high following the immigration, and their population size declined. While Trichuris sp. infections are typically asymptomatic, we consider it a possibility that they contributed to the decline of the black-and-white colobus, and that the red colobus may be serving as a reservoir for Trichuris, thereby increasing the infection risk for black-and-white colobus.

Diet and feeding behavior of Rhinopithecus bieti at Xiaochangdu, Tibet: adaptations to a marginal environment

The diet and feeding ecology of a wild subpopulation of black-and-white snub-nosed monkeys (Rhinopithecus bieti) were studied at Xiaochangdu in Honglaxueshan Nature Reserve, Tibet. This region is climatologically harsher than any other inhabited by non-human primates. Black-and-white snub-nosed monkeys fed on 48 parts of 25 plant species, at least three species of lichens and seven species of invertebrates. The number of food items exploited varied markedly among seasons, with dietary diversity being greatest in spring and summer. In winter, black-and-white snub-nosed monkeys had to subsist on fallback foods such as dried grass and bark. Ubiquitous lichens formed a major dietary constituent throughout the year, contributing about 75% of feeding records. Even though lichens act as a staple, our findings signify that the monkeys at Xiaochangdu prefer feeding on foliage, which is higher in protein content than the former. We provide evidence that black-and-white snub-nosed monkeys are able to cope with an array of food items other than lichens and hence can be regarded as feeding generalists. We discuss the results with reference to previous studies on other subpopulations living in habitats that are floristically more diverse and offer more plant food items than the marginal habitat at Xiaochangdu.

Daily feeding rhythm in proboscis monkeys: a preliminary comparison with other non-human primates

In non-human primates, the daily feeding rhythm, i.e., temporal fluctuation in feeding activity across the day, has been described but has rarely received much analytical interpretation, though it may play a crucial part in understanding the adaptive significance of primate foraging strategies. This study is the first to describe the detailed daily feeding rhythm in proboscis monkeys (Nasalis larvatus) based on data collected from both riverbank and inland habitats. From May 2005 to May 2006, data on feeding behavior in a group of proboscis monkeys consisting of an alpha-male, six adult females and immatures was collected via continuous focal animal sampling technique in a forest along the Menanggul River, Sabah, Malaysia. In both the male and females, the highest peak of feeding activity was in the late afternoon at 15:00-17:00, i.e., shortly before sleeping. The differences in the feeding rhythm among the seasons appeared to reflect the time spent eating fruit and/or the availability of fruit; clearer feeding peaks were detected when the monkeys spent a relevant amount of time eating fruit, but no clear peak was detected when fruit eating was less frequent. The daily feeding rhythm was not strongly influenced by daily temperature fluctuations. When comparing the daily feeding rhythm of proboscis monkeys to that of other primates, one of the most common temporal patterns detected across primates was a feeding peak in the late afternoon, although it was impossible to demonstrate this statistically because of methodological differences among studies.

Learning the ropes: The ontogeny of locomotion in red-shanked douc (Pygathrix nemaeus), Delacour's (Trachypithecus delacouri), and Hatinh langurs (Trachypithecus hatinhensis) I. positional behavior

Recent studies at the Endangered Primate Rescue Center (EPRC) in the Socialist Republic of Vietnam's Cuc Phuong National Park by Byron et al. ([2002] Am. J. Phys. Anthropol. [Suppl.] 34:51) and Covert and Byron ([2002] Caring for Primates) revealed unexpected locomotor and postural behaviors in the red-shanked douc langur (Pygathrix nemaeus). This paper further elucidates the question of red-shanked douc suspensory behavior, and provides initial positional behavior data for two other rare Asian colobines, by comparing the ontogenetic positional behavior of red-shanked douc langurs, Delacour's langurs (Trachypithecus delacouri), and Hatinh langurs (Trachypithecus hatinhensis) at the EPRC. Two hundred and seven hours of positional behavior data were collected, with approximately equal amounts of data on each species, and equal amounts on adults and those less than 18 months in age. All young animals were more active than adults, used a wider repertoire of locomotor behaviors, and expressed suspensory behaviors more frequently than did the adults. Young animals also "invented" one new locomotor and two new postural behaviors. These differences are due to both play and explorative behavior, as well as to the youths' changing musculoskeletal systems. The number of positional behaviors utilized by the adults of these species is quite similar to one another (23-32), as is that utilized by the young (51-56). Douc langurs in both age categories used suspensory behaviors more frequently than did Delacour's and Hatinh langurs. Because the uniformity of enclosures offers a control, the results of this study generate hypotheses regarding adaptive radiations and niche partitioning in wild populations.

Handedness in nature: first evidence on manual laterality on bimanual coordinated tube task in wild primates

Handedness is a defining feature of human manual skill and understanding the origin of manual specialization remains a central topic of inquiry in anthropology and other sciences. In this study, we examined hand preference in a sample of wild primates on a task that requires bimanual coordinated actions (tube task) that has been widely used in captive primates. The Sichuan snub-nosed monkey (Rhinopithecus roxellana) is an arboreal Old World monkey species that is endemic to China, and 24 adult individuals from the Qinling Mountains of China were included for the analysis of hand preference in the tube task. All subjects showed strong individual hand preferences and significant group-level left-handedness was found. There were no significant differences between males and females for either direction or strength of hand preference. Strength of hand preferences of adults was significantly greater than juveniles. Use of the index finger to extract the food was the dominant extractive-act. Our findings represent the first evidence of population-level left-handedness in wild Old World monkeys and broaden our knowledge on evaluating primate hand preference via experimental manipulation in natural conditions.

Preliminary results from a field study of wild Guizhou snub-nosed monkeys (Rhinopithecus brelichi)

The Guizhou snub-nosed monkey, Rhinopithecus brelichi, is a large-bodied colobine confined to the subtropical semi-deciduous forests of Fanjing Mountain Reserve in Guizhou province, southwest China. Field work beginning in 1979 and including 10 months of intensive study in 1991 has revealed several aspects of the behavior and ecology of this species that are distinct from other colobines, including the closely related species R. roxellana and R. bieti. The Guizhou snub-nosed monkey is arboreal, traveling through the trees by quadrupedal walking, climbing, leaping, semibrachiation and (occasionally) by full brachiation. Terrestrial locomotion is use occasionally. Social organization centers around family groups of 5-10 individuals with a single adult male. Many family groups range and rest together in large, semicohesive bands. These bands may split up or coalesce temporarily to form large aggregations of over 400 animals and perhaps more. All-male groups of 2-5 adult or subadult males are found on the periphery of the bands.

Agonistic behavior and dominance relationships in female phayre's leaf monkeys - preliminary results

Socioecological theory suggests a link between the strength of competition for food/safety, rates of agonism, structure of dominance hierarchies, and dispersal among group-living females. This study presents preliminary data on agonistic behavior and dominance relationships for female Phayre's leaf monkeys (Trachypithecus phayrei), a species in which females routinely disperse. Behavioral observations were conducted on two groups (four adult females, and five adult females plus two juvenile females, respectively) at Phu Khieo Wildlife Sanctuary, northeast Thailand. Rates of agonistic behavior were analyzed from focal continuous recordings, while dominance hierarchies were constructed from all agonistic behaviors (focal and ad libitum sampling). Overall, female-female agonistic behaviors (aggression, submission, and displacements) occurred at a rate of < 0.25 interactions per hour. Agonistic interactions involving food occurred more frequently than expected based on feeding time. Females in both groups exhibited linear dominance hierarchies with some reversals, and possibly an age-inversed hierarchical structure in the larger group. The results fit well with previous results for colobine monkeys regarding frequency of interactions, displacements predominating agonistic behavior, and the possibility of an age-inversed hierarchy. The results contradict the suggested link between linearity of hierarchies and female philopatry. Future studies should consider the notion that female dispersal may coexist with linear dominance hierarchies.

Digestion of selected foods by Yunnan snub-nosed monkey Rhinopithecus bieti (Colobinae)

Three digestion trials were conducted to quantify aspects of digestive physiology in the Yunnan snub-nosed monkey Rhinopithecus bieti, a foregut fermenter that feeds primarily on lichens. Mean retention time (MRT, the average time plastic markers spent in the animal) had a mean estimate of 47 hr (n = 3) with high variability between trials (standard deviation = 17 hr). Recently captured animals, presumably with gut flora and digestive physiology close to wild animals, had a longer retention time than did long-term captives, although lack of standardization across trials (such as in activity level) confounds analysis. Apparent digestibilities for dry matter (71-80%) were in line with other studies of colobine digestion, but fall below those of ruminant ungulates feeding on lichens. Fecal analysis accurately determined the relative proportions of leaves vs. lichens in diets; mature leaves and lichens were not nutritional equivalents but appeared to be physiological equivalents in terms of digest passage. Fecal analysis does not, however, accurately determine the relative proportions of food types with different digestibilities, such as fruit vs. leaves.

The effect of forest clear-cutting on habitat use in Sichuan snub-nosed monkey (Rhinopithecus roxellana) in Shennongjia Nature Reserve, China

The habitat use of two groups of Sichuan snub-nosed monkey ( Rhinopithecus roxellana) was observed, using the focal group method, for 7 months in four seasons from June 2000 to October 2001. The habitats were classed into primary forest and three successional habitats: after clear-cutting: grassland, shrub forest and young forest. The results showed that the large group of monkeys had larger range areas than the small group in the same season. Both groups had larger range sizes in summer or autumn than in winter or spring. They spent most of their time using primary forest and young forest, rarely used shrub forest and did not use grassland. In each season, they used the habitats non-randomly and preferred primary forest. The preference order of habitats for both groups every season was the same: primary forest > young forest > shrub forest >/= grassland. The results suggested that primary forest was high-quality habitat and should be conserved as a top priority. Clear-cutting would cause habitat loss and habitat fragmentation, and should therefore be prohibited. High-quality habitat for the monkeys is difficult to restore from clear-cutting.

Seasonality of matings and births in captive Sichuan golden monkeys (Rhinopithecus roxellana)

This study, based on three years of mating behavior observations and 10 years of birth records, reveals that Sichuan golden monkeys in captivity displayed a marked seasonality of mating behavior and births. The peak of matings occurred around October, and births occurred in March-June. The birth peak followed the mating peak by six to seven months. This seasonal cycle of matings and births was similar to observations made in the wild, where both temperature and food resources were favorable in spring. The time delay between peaks of matings and births was the approximate length of gestation, which implies that mating behavior was concentrated during the period of conception. We suggest that the peak of births in captive Sichuan golden monkeys occurred during the time of year with the most favorable environmental conditions, and the peak of matings corresponded with the period of conception.

Evaluating methods for estimating home ranges using GPS collars: A comparison using proboscis monkeys (Nasalis larvatus)

The development of GPS tags for tracking wildlife has revolutionised the study of home ranges, habitat use and behaviour. Concomitantly, there have been rapid developments in methods for estimating habitat use from GPS data. In combination, these changes can cause challenges in choosing the best methods for estimating home ranges. In primatology, this issue has received little attention, as there have been few GPS collar-based studies to date. However, as advancing technology is making collaring studies more feasible, there is a need for the analysis to advance alongside the technology. Here, using a high quality GPS collaring data set from 10 proboscis monkeys (Nasalis larvatus), we aimed to: 1) compare home range estimates from the most commonly used method in primatology, the grid-cell method, with three recent methods designed for large and/or temporally correlated GPS data sets; 2) evaluate how well these methods identify known physical barriers (e.g. rivers); and 3) test the robustness of the different methods to data containing either less frequent or random losses of GPS fixes. Biased random bridges had the best overall performance, combining a high level of agreement between the raw data and estimated utilisation distribution with a relatively low sensitivity to reduced fixed frequency or loss of data. It estimated the home range of proboscis monkeys to be 24-165 ha (mean 80.89 ha). The grid-cell method and approaches based on local convex hulls had some advantages including simplicity and excellent barrier identification, respectively, but lower overall performance. With the most suitable model, or combination of models, it is possible to understand more fully the patterns, causes, and potential consequences that disturbances could have on an animal, and accordingly be used to assist in the management and restoration of degraded landscapes.

Birth seasonality and interbirth interval of captive Rhinopithecus bieti

This study, which is based on 10 years of birth records, shows that black-and-white snub-nosed monkeys (Rhinopithecus bieti) in captivity display marked birth seasonality. The birth season starts in December and ends in June, with a peak from March to May, and a median birth date of April 10. More male infants than female ones are born in captivity. More males were born at the Kunming Institute of Zoology (KIZ) than at the Kunming Zoo (KZ). Of 17 interbirth intervals (IBIs), 29% were from females that had lost an infant at <1 year of age or experienced stillbirth, and 71% were from females whose infant survived more than 1 year. The mean IBI for the former group (428+/-SD 87 days) was significantly shorter than that for the latter group (706+/-71 days), in agreement with reports of other Colobine species. Infant mortality was lower in captivity than in the field, which may reflect the relatively stable food availability and climate in captivity compared to the harsh conditions in the wild.

Examining the extinction risk of specialized folivores: a comparative study of Colobine monkeys

Species extinctions are nonrandom with some taxa appearing to possess traits that increase their extinction risk. In this study, eight predictors of extinction risk were used as independent variables to predict the IUCN category of a subfamily of specialized folivorous primates, the Colobinae. All data were transformed into phylogenetically independent contrasts and were analyzed using bivariate regressions, multiple regression, and a maximum likelihood approach using Akaike's Information Criterion to assess model performance. Once an outlier was removed from the data set, species that devote a smaller proportion of their diet to mature leaf consumption appear to be at a greater risk of extinction. Also, as female body mass increases, so does extinction risk. In contrast, as maximum latitude and the number of habitat types increase, extinction risk appears to decrease. These findings emphasize the importance of examining detailed dietary variation for predicting extinction risk at a relatively fine taxonomic scale and, consequently, may help improve conservation management.

Male cooperation for breeding opportunities contributes to the evolution of multilevel societies

A small number of primate species including snub-nosed monkeys (colobines), geladas (papionins) and humans live in multilevel societies (MLSs), in which multiple one-male polygamous units (OMUs) coexist to form a band, and non-breeding males associate in bachelor groups. Phylogenetic reconstructions indicate that the papionin MLS appears to have evolved through internal fissioning of large mixed-sex groups, whereas the colobine MLS evolved through the aggregation of small, isolated OMUs. However, how agonistic males maintain tolerance under intensive competition over limited breeding opportunities remains unclear. Using a combination of behavioural analysis, satellite telemetry and genetic data, we quantified the social network of males in a bachelor group of golden snub-nosed monkeys. The results show a strong effect of kinship on social bonds among bachelors. Their interactions ranged from cooperation to agonism, and were regulated by access to mating partners. We suggest that an 'arms race' between breeding males' collective defence against usurpation attempts by bachelor males and bachelor males' aggregative offence to obtain reproductive opportunities has selected for larger group size on both sides. The results provide insight into the role that kin selection plays in shaping inter-male cohesion which facilities the evolution of multilevel societies. These findings have implications for understanding human social evolution, as male-male bonds are a hallmark of small- and large-scale human societies.

What Hanuman langur males know about female reproductive status

In species with a high risk of infanticide, a conflict of interest exists between the sexes over the amount of paternity information that is available to males. While females are expected to keep males unaware of their reproductive status in order to confuse paternity, selection should favor those male traits that enhance the males' assessment of female status and consequently of paternity probability. In Hanuman langurs (Semnopithecus entellus), a species that is extremely vulnerable to infanticide, females have been shown to successfully conceal the exact timing of ovulation from males--perhaps because they exhibit no sexual swelling and mate during all reproductive phases, including gestation. Nevertheless, it remains unclear whether males have hitherto unrecognized information about females' reproductive condition on a broader level that could still enhance male reproductive success. We investigated male assessment of female reproductive states in a population of wild Hanuman langurs as indicated by changes in male behavior, such as rates of copulations, anogenital inspections, and consortships, in relation to different female receptive periods (pregnant, fertile-nonconceptional, and conceptional). Our data indicate that males were able to discern qualitatively distinct reproductive states. Males were more interested in fertile than pregnant females, as indicated by higher copulation rates. Based on consortships, males distinguished fertile from nonfertile phases, as well as fertile, nonconceptional receptive periods from conceptional ones. Hanuman langur males are thus not as unaware of female reproductive condition as previously thought, supporting the idea of an ongoing battle of the sexes over paternity information. However, granting some knowledge while at the same time concealing the exact day of ovulation may also reflect a pure female strategy of balancing paternity concentration with paternity confusion, which is the most likely strategy in this system with high infanticide risk and male defense of infants.

Female transfer between one-male groups of proboscis monkey (Nasalis larvatus)

Successful or unsuccessful female transfers were observed seven times during a 32-month field study of proboscis monkeys (Nasalis larvatus) inhabiting a riverine forest along a tributary of the Kinabatangan River, Sabah, Malaysia. In all cases, the females voluntarily left their own groups and immediately joined with another one. When adult females tried to shift to other groups, adult males called them back to their own groups, but appeared to be indifferent to subadult females. When the adult females returned, the males never attacked the females physically, but instead often emitted herding sounds to them. One subadult female was repelled by a resident adult female. When one adult female transferred into a new one-male group, she left her behind son in an all-male group. The number of females often fluctuated in most study groups, with this fluctuation being more prominent among subadult females than adult females. It is likely that female transfer in proboscis monkeys is not a rare occurrence and that it is especially common among sub-adult females.

Patch depletion behavior differs between sympatric folivorous primates

Food competition in group-living animals is commonly accepted as a critical determinant of foraging strategies and social organization. Here we examine food patch depletion behavior in a leaf-eating (folivorous) primate, the guereza (Colobus guereza). Snaith and Chapman (2005) studied the sympatric folivorous red colobus (Procolobus rufomitratus), which shares many food resources with the guereza. They determined that red colobus deplete the patches (feeding trees) they use, while we found contrary evidence for guerezas using the same methods. We found that the time guerezas spent feeding in a patch was affected by neither tree size, an indicator of food abundance, nor the size of the feeding group, an indicator of feeding competition. For their principal food item (young leaves), intake rate remained constant and coincided with a decrease in the distance moved to find food within a patch, implying that guerezas do not deplete patches. This points to a fundamental difference in the use of food by guerezas and red colobus, which may be linked to the large difference in their group sizes and/or to a disparity in their digestive physiologies. However, further analyses revealed that the number of feeders within a patch did not affect patch depletion patterns in either species, leaving the potential for a physiological basis as the most plausible explanation. Our research highlights the need for a more critical examination of folivorous primate feeding ecology and social behavior, as all folivorous primates are typically lumped into a single category in socioecological models, which may account for conflicting evidence in the literature.

Distribution and conservation status of Rhinopithecus strykeri in China

This paper summarizes the results of 358 interviews we conducted on Rhinopithecus strykeri in the Gaoligong Mountains, northwest Yunnan, China, between April 2011 and December 2012. Based on our interview records and selective field surveys (47 days of field survey for seven possible distribution areas), we suggest that there may be up to 10 groups of R. strykeri occurring in China between the Salween River and the border with Myanmar, and that the total population of R. strykeri in China should be between 490 and 620 animals. According to interviewees, Rhinopithecus strykeri tends to use conifer and mixed conifer-broad-leaved forest, predominantly between 2,600 and 3,100 m above sea level. To better protect this globally threatened species, classified as critically endangered by the International Union for Conservation of Nature (IUCN), we suggest extensions to current nature reserve boundaries to better include the home ranges of China's remaining population.

Phytochemicals and reproductive function in wild female Phayre's leaf monkeys (Trachypithecus phayrei crepusculus)

Female reproduction is known to be influenced by food availability and its impact on energetic status. However, emerging evidence suggests that the phytochemical content of food may also be an important factor. Here, we investigated this hypothesis, presenting 20 months of data on fecal progestin (fP) patterns in wild female Phayre's leaf monkeys (Trachypithecus phayrei crepusculus). We examined whether (a) the availability of Vitex (a plant known to contain phytochemicals) might be linked to seasonal fP levels, (b) fP levels were associated with female reproductive performance, and (c) reproductive performance might also be linked with energetic status (as measured by physical condition). We collected fecal samples (N=2077) from 10 adult females to analyze estrogen (fE) and progestin (fP) metabolites, behavioral data from 7 cycling females to determine receptivity, and monthly data on Vitex availability and female physical condition. Seasonally elevated fP levels were found in all females, with higher levels when Vitex leaves and fruits were abundant. During the period of high progestins, females had longer cycle lengths and follicular phases, while receptive periods did not change. Nevertheless, when ovulations occurred, females were more likely to conceive. On the other hand, conceptions were also more likely when physical condition was improving, suggesting that the effects of phytochemicals and energetic status on reproduction may be difficult to separate. Although our results support the predicted effects of Vitex on endocrine and reproductive function, future studies with detailed feeding data and chemical analyses of plants are needed to confirm this finding.