Showing papers in "Primates in 2007"

Chimpanzees (Pan troglodytes) learn to act with other individuals in a cooperative task

Abstract: We presented two chimpanzees with a task in which they were required to pull each end of a rope simultaneously to drag blocks supporting food into reach. The chimpanzees did not succeed in initial tests. They did not immediately understand the necessity for cooperation, and they did not adjust their behavior to work with the partner. However, the frequency of success gradually increased as the number of sessions increased and the task was varied. They began to look at the partner frequently, wait if the partner was not holding the rope, and pull the rope in synchrony with the partner. However, they did not use interactive behaviors or eye contact to synchronize their behavior. One chimpanzee was then paired with a human partner in the same situation. After initial failures, the chimpanzee began to solicit the human partner for cooperation: looking up at his face, vocalizing, and taking the partner's hand. When this chimpanzee was again paired with the chimpanzee partner, no soliciting behavior was observed. Thus, the chimpanzees could learn to coordinate their behavior through trial and error. Communicative behavior emerged during the task, but the communication differed according to the identity of the partner.

Do age- and sex-related variations reliably reflect body size in non-human primate vocalizations? A review

Abstract: In vocal communication, the mechanisms of sound production are well understood. The length of the vocal folds determines the minimum fundamental frequency, while the size and the shape of the vocal tract affect its filtering characteristics and hence, the resonant frequencies. Both measures—vocal fold length and vocal tract length—are related to body size and therefore, acoustic features are expected to vary with body size. Because direct measures of body size are difficult to obtain from free-ranging animals, age and sex have often been used as proxies. We surveyed studies which included direct measures of size or weight, and also studies in which only age and/or sex differences were examined. The main purpose was to examine whether age- and sex-related variations in acoustic features meet the predictions generated from our knowledge about sound production. Our survey revealed that compared to smaller animals, larger animals utter longer calls, with a lower fundamental frequency, with smaller formant dispersion, and with the energy concentrated in lower frequencies. Age and sex reliably reflect the influence of body size on acoustic features when gross size differences are examined. However, within age- and sex classes, this relationship may break down. In addition to body size, other factors such as internal state or social context may also influence the structure of vocal signals and highlight the richness of information in calls that is potentially available to listeners.

Variation in diet and ranging of black and white colobus monkeys in Kibale National Park, Uganda.

Abstract: Recently, considerable intraspecific variation in the diets and ranging behavior of colobine monkeys has been described, although in most cases this has involved documenting variation between, not within, sites. Some African colobines, such as guerezas (Colobus guereza), are relatively abundant in disturbed habitats that are very heterogeneous, raising the intriguing possibility that even groups with overlapping home ranges may exhibit large behavioral differences. If such differences occur, it will be important to understand what temporal and spatial scales adequately portray a species’ or population’s diet and ranging behavior. This study documents within-site variation in the diet and ranging behavior of guerezas in the habitat types in which they are described to be most successful—forest edge and regenerating forest. We collected data on eight groups of guerezas with overlapping home ranges for 3–5 months each in Kibale National Park, Uganda. The guerezas were highly folivorous, with leaves constituting 78.5–94.0% of the groups’ diets. The percentage of mature leaves and fruit in the diet varied widely among and within groups. We show that differences among groups in the intensity with which they fed on specific tree species were not just related to phenology, but also to differences in the forest compositions of groups’ core areas. Range size estimates varied more than fivefold among groups and the minimum distance from groups’ core areas to eucalyptus forest (which all groups regularly fed in) was a better predictor of range size than was group size. These results reveal considerable variation in the diet and ranging behavior among groups with overlapping ranges and have implications for comparative studies, investigations of within- and between-group feeding competition, and the potential for populations to adapt to anthropogenic or natural environmental change.

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

Abstract: 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.

Evidence of cave use by savanna chimpanzees (Pan troglodytes verus) at Fongoli, Senegal: implications for thermoregulatory behavior.

Abstract: Much attention has been paid to how humans both adapt and acclimate to heat stress, primarily due to the relevance of these issues to hominid evolution in open Plio-Pleistocene environments. However, little is known about the responses of human's closest living relative, the chimpanzee (Pan troglodytes), to similar environmental stressors. In southeastern Senegal, one of the hottest and driest habitats that chimpanzees (P. t. verus) live in today, apes rely on behavioral mechanisms of dealing with ther- mal stress. Chimpanzees' use of caves was based primarily on indirect evidence (feeding traces, feces, and hairs) gathered from one cave from January to December 2004, but data from observational records collected from May 2001 through March 2006 supplement these data. The hypothesis that chimpanzees' use of caves is a response to heat was tested by collecting data on temperatures within the largest cave and in different habitats used by chim- panzees, such as gallery forest and woodland. Results indicate that chimpanzees primarily use caves as shelters during the hottest times of year and that caves are consis- tently and significantly cooler than open habitats. Insight into the way that chimpanzees in Senegal cope with ex- treme temperatures may help us to better understand the behavior of early hominids in such an environment.

Movement and resource use by a group of Alouatta pigra in a forest fragment in Balancán, México.

Abstract: Uncommonly observed behaviors were systematically recorded in a troop (n = 9 individuals) of black howler monkeys (Alouatta pigra) inhabiting a small forest fragment (17 ha) in Leona Vicario, Balancan, Tabasco, Mexico Between February 2002 and January 2003 (n = 499 h), we observed behaviors such as ground travel (85 occasions, total = 269 min/108% of total locomotion time), ground foraging (eight occasions, total = 50 min/084% of total feeding time) and drinking water pooled in tree holes (20 times, total = 93 min/031% of total activity time) Total time (412 min) for these non-resting behaviors (feeding and locomotion on the ground) is almost equivalent to time devoted to social activities (420 min) These behaviors indicate that howler monkeys may be responding to pressures imposed by the small size of the fragment by adopting diverse strategies to cover their basic nutritional needs in this environment They accomplish this while exposing themselves to potential predation by coyotes (Canis latrans), as was observed once during the study It is likely that these behaviors are occurring at an increasing rate among monkeys in fragmented landscapes

Postglacial population expansion of Japanese macaques (Macaca fuscata) inferred from mitochondrial DNA phylogeography

Abstract: We investigated the diversity and phylogeography of mitochondrial DNA (mtDNA) in Japanese macaques (Macaca fuscata), an endemic species in Japan that has the northernmost distribution of any non-human primate species. DNA samples from 135 localities representing the entire range of this species were compared. A total of 53 unique haplotypes were observed for the 412-bp partial mtDNA control region sequence, with length variation distinguishing the two subspecies. Clustering analyses suggested two putative major haplogroups, of which one was geographically distributed in eastern Japan and the other in western Japan. The populations in the east showed lower mtDNA diversity than those in the west. Phylogeographical relationships of haplotypes depicted with minimum spanning network suggested differences in population structure. Population expansion was significant for the eastern but not the western population, suggesting establishment of the ancestral population was relatively long ago in the west and recent in the east. Based on fossil evidence and past climate and vegetation changes, we inferred that the postulated population expansion may have taken place after the last glacial period (after 15,000 years ago). Mitochondrial DNA showed contrasting results in both variability and phylogenetic status of local populations to those of previous studies using protein variations, particularly for populations in the periphery of the range, with special inference on habitat change during the glacial period in response to cold adaptation.

Sympatry between Alouatta caraya and Alouatta clamitans and the rediscovery of free-ranging potential hybrids in Southern Brazil

Abstract: Records of sympatry between Alouatta caraya and A. clamitans are rare despite their extensive range overlap. An example of their current sympatry and the rediscovery of free-ranging potential hybrids of A. caraya and A. clamitans in the forests of the Upper Parana River, Southern Brazil, are reported in this paper. Eight groups were observed in the study area: five monospecific groups of A. caraya, two of A. clamitans, and a group containing two adult males and two adult females of A. caraya and a sub-adult male and two adult females identified as Alouatta sp. The color of the last three individuals was a mosaic between the two species; this is consistent with previously described variations in museum specimens collected in the Parana River in the 1940s that had been identified as potential hybrids. The results from this study emphasize the need for scientific studies in the region of the Ilha Grande National Park, one of the few regions in the Parana River that currently harbors both howler species.

Chimpanzee grouping patterns and food availability in Mahale Mountains National Park, Tanzania.

Abstract: The aim of this study was to test for a correlation between party size and food (fruit) availability among the M group chimpanzees (Pan troglodytes) in the Mahale Mountains, Tanzania. Chimpanzee unit groups (or communities) show fission–fusion grouping patterns and form temporal parties. Fruit availability is assumed to be one of the important limiting factors in relation to the size of these parties. Different methods have been proposed to measure party size, but they all appear to focus mainly on two aspects of grouping phenomena. In “face-to-face parties”, party size is measured by scan sampling, whereas in “nomadic parties”, all members observed during a specific time period are counted. The mean monthly group size resulting from these two measures was compared with fruit availability, i.e. fruiting plant density and mean potential patch size. Nomadic party size was correlated with both values. Thus, party formation at this level was considered to be sensitive to overall fruit availability in the habitat. On the other hand, face-to-face party size remained stable and showed weak or no correlations with density and potential patch size. Although large patches are available during the peak fruiting season, Mahale chimpanzees depend on the liana species Saba comorensis, which, when fruiting, encourages individuals to spread out to eat. Thus, the lack of correlation between face-to-face-party size and fruit availability was attributed to the influence of physical limitations countervailing the fluctuation in fruit availability. Maximum face-to-face party size relative to unit-group size, regarded as the cohesiveness of a unit group, was compared among sites. The values differed largely: Mahale groups M and K, Bossou, and, in some years, Budongo, showed high cohesiveness, while others remained low. Thus, the distribution of the most important food during the fruiting season in each study site may be a crucial factor in the grouping phenomena of chimpanzees.

Bed and bed-site reuse by western lowland gorillas ( Gorilla g. gorilla ) in Moukalaba-Doudou National Park, Gabon

Abstract: In this paper we describe bed (nest) and bed-site reuse by western lowland gorillas (Gorilla g. gorilla) in Moukalaba-Doudou National Park, south-eastern Gabon. During an eight-month study 44 bed sites and 506 beds were found. Among these, 38.6% of bed sites and 4.1% of beds were reused. We analyzed the monthly frequency of bed-site reuse in relation to rainfall, fruit abundance, and fruit consumption by the gorillas. The different frequency of bed-site reuse in the rainy and dry seasons was not significant. More bed-site reuse was observed during the fruiting season than during the non-fruiting season. Results from fecal analysis suggested that gorillas ate more fruit in the fruiting season than in the non-fruiting season. The frugivorous diet of western gorillas may possibly cause gorillas to stay in some areas and, consequently, reuse their bed sites. Reuse of bed sites by gorillas suggests their frequent return to an area where preferred fruit is readily available. A higher percentage of arboreal beds may also affect bed-site reuse, because of the shortage of bed material.

Ant fishing by wild chimpanzees is not lateralised.

Abstract: Right-dominant handedness is unique and universal in Homo sapiens, suggesting that it is a highly derived trait. Our nearest living relations, chimpanzees, show lateralised hand preference when using tools, but not when otherwise manipulating objects. We report the first contrary data, that is, non-lateralised tool-use, for ant fishing as done in the Mahale Mountains of Tanzania. Unlike nut cracking, termite fishing, and fruit pounding, as seen elsewhere, in which most individuals are either significantly or wholly left- or right-biassed, ant fishers are mostly ambilateral. The clue to this exception lies in arboreality; all other patterns of chimpanzee elementary technology are done on the ground. Arboreal tool use usually requires not only that one hand be used to hold the tool, but also that the other hand gives postural support. When the supporting hand is fatigued, then it must be relieved by the other. Terrestrial tool use entails no such trading off. To test the hypothesis, we compared frequency of hand changing with the incidence of major hand support, and found them to be significantly positively correlated. The evolutionary transition from arboreality to terrestriality may have been a key enabler for the origins of human laterality.

Copulation behavior within one-male groups of wild Rhinopithecus roxellana in the Qinling Mountains of China

Abstract: This study was conducted using focal animal sampling on the west ridge group of the Sichuan snub-nosed monkey (Rhinopithecus roxellana) located in the Zhouzhi National Nature Reserve on the north slope of the Qinling Mountains, from 8 July 2003 to 24 May 2004. The difference in the average frequency of copulations for each focal male for each month was significant (F = 3.068, P = 0.016, one-way ANOVA test) with the majority of copulations occurring between September and November. Duration of intromission ranged from 2 to 39 s, with a mean of 16.0 ± 0.4 s. Females initiated 627 courtship attempts (96.2%), while males only initiated 3.8%. Both adult females (72.8%) and sub-adult females (27.2%) were involved in sexual interference acts. Females who gave birth in 2004 performed more sexual interference acts than would be expected by chance in the reproductive period of 2003 (X 2 = 13.73 > X 2 0.005,2, df = 2, P < 0.005). Male response to female interference was equally divided into “solicitor mounting” and “interrupter mounting”. The resident males of one-male units were not observed to mount both the solicitor and the interrupter or mount neither following female solicitation interruptions. Three post-conception copulations were also observed in this study. These results suggest a skewed sexual competition, with multiple females competing for a single male, which was shown by courtship attempts and female interference.

Visual search for orientation of faces by a chimpanzee (Pan troglodytes): face-specific upright superiority and the role of facial configural properties.

Abstract: A previous experiment showed that a chimpanzee performed better in searching for a target human face that differed in orientation from distractors when the target had an upright orientation than when targets had inverted or horizontal orientation [Tomonaga (1999a) Primate Res 15:215–229]. This upright superiority effect was also seen when using chimpanzee faces as targets but not when using photographs of a house. The present study sought to extend these results and explore factors affecting the face-specific upright superiority effect. Upright superiority was shown in a visual search for orientation when caricaturized human faces and dog faces were used as stimuli for the chimpanzee but not when shapes of a hand and chairs were presented. Thus, the configural properties of facial features, which cause an inversion effect in face recognition in humans and chimpanzees, were thought to be a source of the upright superiority effect in the visual search process. To examine this possibility, various stimuli manipulations were introduced in subsequent experiments. The results clearly show that the configuration of facial features plays a critical role in the upright superiority effect, and strongly suggest similarity in face processing in humans and chimpanzees.

The breeding system of wild red ruffed lemurs ( Varecia rubra ): a preliminary report

Abstract: Captive studies have shown that ruffed lemurs (Varecia) have an unusual suite of reproductive traits combined with extremely high maternal reproductive costs. These traits include the bearing of litters, nesting of altricial young, and absentee parenting. To characterize the breeding system of this enigmatic lemur, reproductive traits must be contextualized in the wild. Here, I provide a preliminary report of mating and infant care in one community of wild red ruffed lemurs (Varecia rubra). Observations span a 15-month period covering two birth seasons and one mating season on the Masoala Peninsula, Madagascar. Factors that are not possible to replicate in captivity are reported, such as mating pattern, natality and mortality rates, the location of nests within the home range, and the structuring of infant care within a natural community. V. rubra at Andranobe have a fission-fusion, multifemale-multimale grouping pattern and a polygamous mating system. They do not mate monogamously or live strictly in family-based groups as suggested by previous workers. During the first 2 months of life, nests and infant stashing localities are situated within each mother’s respective core area, and inhabitants of each core area within the communal home range provide care for young. As part of their absentee parenting system, infants are left in concealed, protected, and supportive spots high in the canopy, while mothers travel distantly. This practice is termed ‘infant stashing’. Alloparenting appears to be an integral part of V. rubra’s overall reproductive strategy in the wild, as it was performed by all age-sex classes. Among the alloparental behaviors observed were infant guarding, co-stashing, infant transport, and allonursing. Alloparenting and absentee parenting may mitigate high maternal reproductive costs. Furthermore, V. rubra may have a breeding system in which genetic partners (i.e., mating partners) do not always correspond to infant care-providers. Combined with recently available information on the behavioral ecology of wild ruffed lemurs, this preliminary report suggests directions for in-depth studies on Varecia’s breeding system.

Leaf-swallowing in Nigerian chimpanzees: evidence for assumed self-medication

Abstract: A field study in Gashaka, Nigeria, adds the fourth subspecies of chimpanzee, Pan troglodytes vellerosus, to the list of African ape populations in which leaf-swallowing occurs. Unchewed herbaceous leaves of Desmodium gangeticum (Leguminosae-Papilionoideae) were recovered in 4% of 299 faecal samples of wild chimpanzees and clumps of sharp-edged grass leaves in 2%. The ingestion is believed to serve self-medicatory purposes because the leaves had a rough surface or were sharp-edged (which could be related to parasite control through a self-induced increase of gut motility), were not chewed, were excreted whole (indicating that they were not ingested for nutritional purposes), leaf-swallowing was restricted to the rainy season (during which time parasite re-infections are more common), and parasitic worms (Oesophagostomum stephanostomum) were found together with the leaves.

Wild chimpanzee infant urine and saliva sampled noninvasively usable for DNA analyses.

Abstract: In many genetic studies on the great apes, fecal or hair samples have been used as sources of DNA. However, feces and hairs are difficult to collect from chimpanzee infants under 3 years of age. As alternative DNA sources, we investigated the efficiency of collecting urine samples from infants compared with fecal samples, as well as the validity of the DNA extracted from urine and saliva samples of well-habituated M group chimpanzees (Pan troglodytes schweinfurthii) in the Mahale Mountains National Park, Tanzania. We collected 40 urine and 3 fecal samples from 10 infants under 3 years. Compared with feces, the urine samples were relatively easy to collect. The saliva of infants, which remained on the twigs sucked by them, was collected using cotton swabs. The average amounts of DNA extracted from the 40 urine and 6 saliva samples were 3,920 and 458 pg/μl, respectively. The rate of positive PCR was low and the allelic dropout rate was high when using less than 25 pg of template DNA in the PCR mixtures. Based on the amounts of DNA, 50% of the urine samples and 100% of the saliva samples were judged usable for accurate microsatellite genotyping. For infant chimpanzees in particular, collecting urine and saliva as an alternative to fecal and hair samples can reduce the effort invested in collection in the field.

Non-reproductive copulation behavior among Tibetan macaques (Macaca thibetana) at Huangshan, China

Abstract: Non-reproductive copulation, which takes place outside of the mating season and does not result in conception and birth, was studied in a free-ranging group of Tibetan monkeys (Macaca thibetana) at Mt. Huangshan, China, in the birth seasons of 1992 and 1997. We employed all occurrence and focal animal samplings to record sexual and related behaviors and affiliation interactions, respectively. Compared with sexual behavior in mating season, non-reproductive copulation occurred at a lower frequency, with less frequent ejaculation, less harassment, shorter mount duration, and an absence of pause with vocalization. It often took place in a situation in which non-lactating females were involved in social conflict or approached males for mating. Neither pregnant nor lactating females were observed to mate in the birth seasons. Copulation during the birth season did not increase a sexually receptive female’s delivery the next year, nor was it associated with increased proximity, grooming, or agonistic aid for the mating pair. However, copulated pairs spent more time co-feeding, presumably reflecting an increased tolerance on the part of the male. Adolescent males, who rarely copulated in the mating season, engaged in mating activity in birth seasons as well. Therefore, though birth-season copulation had no reproductive functions, it may have fulfilled social functions for females, such as post-aggression appeasing by males or gaining access to resources. This also offered good opportunities for adolescent males and females to develop their sexual skills for later competition.

Terrestriality and tree stratum use in a group of Sichuan snub-nosed monkeys

Abstract: Morphological characters allow the Sichuan snub-nosed monkey (Rhinopithecus roxellana) to use multiple tree levels, but very few studies have quantified the terrestriality and tree stratum use of the species. I investigated the terrestriality and tree stratum use in a group of the monkeys from July 2003 to September 2004 (except February) in the Qianjiaping area of Shennongjia Nature Reserve, China. I collected data on the vertical position of individual monkeys in forest in relation to behavior types, diet, age/sex classes, vegetation types, tree height, and distribution of predators. The monkeys were much more arboreal than they were thought to be. They spent 97.1% of their time in trees (n = 21,234 records) and 2.9% on the ground, and mainly used the middle (74.4%) and upper strata (17.4%). The monkeys displayed all behavioral types except searching in the middle and upper strata. The percentage of use of a stratum (except the low stratum) varied among months, and there was a difference in the percentage of use of a stratum among age/sex classes and between vegetation types. Approximately 94.2% of trees used by the monkeys were >6 m tall. They mainly fed on lichens, young leaves, mature leaves, flowers, fruits or seeds, and buds in the middle and upper strata, bark in the low and middle strata and herbs on the ground. Wolf (Canis lupus), leopard (Panthera pardus), and golden eagle (Aquila chrysaetos) are predators threatening the survival of individual monkeys in the study site. The results suggested that the seasonal vertical distribution of food items eaten in forest, predators, and vegetation types had important effects on the terrestriality and tree stratum use of the monkeys.

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

Abstract: 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.

Interactions between tayras (Eira barbara) and red-handed howlers (Alouatta belzebul) in eastern Amazonia.

Abstract: Two tayras (Eira barbara) were observed attacking an infant red-handed howler (Alouatta belzebul) on an island in eastern Brazilian Amazonia, as a nearby adult male watched passively. In a separate incident, four tayras were seen attacking a subadult female on the ground. Tayras were also observed in the vicinity of the two howler study groups on a number of occasions over a 9-month period. During this same period, the two groups lost a third of their members, including infants and subadults, and the remains of six animals were found at the study site. While tayras were the only predators seen attacking the howlers, it remains unclear to what extent they were responsible for apparently high mortality rates in this high-density, isolated howler population.

High population density of black-handed spider monkeys (Ateles geoffroyi) in Costa Rican lowland wet forest.

Abstract: The main objective of this study was to estimate the population density and demographic structure of spider monkeys living in wet forest in the vicinity of Sirena Biological Station, Corcovado National Park, Costa Rica. Results of a 14-month line-transect survey showed that spider monkeys of Sirena have one of the highest population densities ever recorded for this genus. Density estimates varied, however, depending on the method chosen to estimate transect width. Data from behavioral monitoring were available to compare density estimates derived from the survey, providing a check of the survey’s accuracy. A combination of factors has most probably contributed to the high density of Ateles, including habitat protection within a national park and high diversity of trees of the fig family, Moraceae. Although natural densities of spider monkeys at Sirena are substantially higher than those recorded at most other sites and in previous studies at this site, mean subgroup size and age ratios were similar to those determined in previous studies. Sex ratios were similar to those of other sites with high productivity. Although high densities of preferred fruit trees in the wet, productive forests of Sirena may support a dense population of spider monkeys, other demographic traits recorded at Sirena fall well within the range of values recorded elsewhere for the species.

Ranging behavior of the François’ langur (Trachypithecus francoisi) in the Fusui Nature Reserve, China

Abstract: Data on activity budgets and ranging patterns were collected from March to December 2001 for one group of Francois’ langurs (Trachypithecus francoisi) inhabiting a forested part of the Fusui Nature Reserve, Guangxi province, China. Our results indicate that the total size of the home range of the study group during the study period was 19 ha. The majority of their activities (52%) occurred within a small area, 22%, of their home range, and was concentrated in or near quadrats containing their sleeping sites, which may reduce the time and energetic cost of travel. The extent of the ranging behavior varied between months, with the smallest, 7 ha, recorded in July and the largest, 13.5 ha, in November. There was no significant difference between seasons. The monthly mean daily path lengths varied from 341 to 577 m. The daily path lengths showed significant seasonal changes: the path lengths were longer during the dry season than in the rainy season, which may be related to the scarcity of preferred food resources during the dry season.

Effects of male group size, parity, and cycle stage on female chimpanzee copulation rates at Ngogo, Kibale National Park, Uganda

Abstract: Chimpanzees have complex and variable mating strategies, but most copulations occur when females with full sexual swellings are in parties with multiple males and mate with most or all of those males. Daily copulation rates for fully swollen females vary at different times of a female's cycle, among females, and across communities and populations. Variation in female age, parity, and cycle stage underlie some of this variation, but possible demographic effects on copulation rates have not been systematically investigated. Demographic variation can affect many aspects of behavior and ecology, including the frequency and success of different mating tactics. Analysis of data from the unusually large chimpanzee community at Ngogo produces two results that are consistent with the hypothesis that demographic variation affects female copulation rates. Copulation rates were high compared with those reported from other research sites, where females had fewer potential mates available. Daily copulation rates of fully swollen females were also positively related to the number of males with whom they associated. Ngogo data also re-confirm results from other studies, of both wild and captive populations, showing that female copulation rates increase during periovulatory periods. This is consistent with the hypothesis that sexual swellings and extended receptivity and proceptivity help to protect females against infanticide by helping to ensure they mate with all potential sires. As at some other sites, parous females at Ngogo copulated at higher rates than nulliparous females. Possible effects of demography on sexual behavior should be considered in assessments of differences between chimpanzees and bonobos and of variation across chimpanzee populations.

The influence of snowfall, temperature and social relationships on sleeping clusters of Japanese monkeys during winter in Shiga Heights.

Abstract: We studied Japanese monkeys (Macaca fuscata) of the Shiga A(1) troop at their sleeping sites in Shiga Heights, Japan, for 41 nights during 3 winters. Monkeys chose their sleeping sites in Japanese cedars and in deciduous broad-leaved forests on non-snowing nights and in Japanese cedar forests on snowing nights. We counted 399 sleeping clusters in which 2 or more monkeys remained in physical contact through the night and 43 solitary sleeping monkeys, though monkeys did not maintain physical contact with others in the daytime. We found 397 clusters on tree branches and 2 clusters on rocks. The mean size of huddling clusters was 3.06+/-1.22 SD. The cluster size (3.17+/-1.26 SD) at lower ambient temperatures between -7 and -4 degrees C was larger than that at higher temperatures between -2 and 4 degrees C (cluster size 2.88+/-1.13 SD). Most clusters were composed of kin. Females kept close to related females in the daytime and huddled with them at night. The highest-ranking male mainly huddled with his kin and his familiar females. Other males kept farther apart from each other in the daytime, probably to avoid social conflicts. Through cold winter nights, however, such males reduced inter-individual distances and huddled with other males. Japanese monkeys appear to recognize three types of inter-individual distances: an intimate distance less than 1 m, a personal distance of 1-3 m and a social distance of 3-20 m; they change their inter-individual distances according to social and ecological circumstances.

Femur length, body mass, and stature estimates of Orrorin tugenensis, a 6 Ma hominid from Kenya.

Abstract: To understand the palaeobiology of extinct hominids it is useful to estimate their body mass and stature. Although many species of early hominid are poorly preserved, it is occasionally possible to calculate these characteristics by comparison with different extant groups, by use of regression analysis. Calculated body masses and stature determined using these models can then be compared. This approach has been applied to 6 Ma hominid femoral remains from the Tugen Hills, Kenya, attributed to Orrorin tugenensis. It is suggested that the best-preserved young adult individual probably weighed approximately 35-50 kg. Another fragmentary femur results in larger estimates of body mass, indicative of individual variation. The length of the femur of the young adult individual was estimated, by using anthropoid-based regression, to be a minimum of 298 mm. Because whole-femur proportions for Orrorin are unknown, this prediction is conservative and should be revised when additional specimens become available. When this predicted value was used for regression analysis of bonobos and humans it was estimated to be 1.1-1.2 m tall. This value should, however, be viewed as a lower limit.

Sniffing behaviors in Mahale chimpanzees

Abstract: Although it is difficult for observers to determine how non-human primates use olfaction in a natural environment, sniffing is one clue. In this study, the sniffing behaviors of wild chimpanzees were divided into six categories, and sex differences were found in most categories. Males sniffed more frequently than females in sexual and social situations, while females sniffed more often during feeding and self-checking. Chimpanzees sniffed more frequently during the dry season than during the wet season, presumably due to the low humidity. This suggests that the environment affects olfactory use by chimpanzees and that chimpanzees easily gather new information from the ground via sniffing.

The distributions of howling monkeys (Alouatta pigra and A. palliata) in southeastern Mexico and Central America.

Abstract: We compared the distributions of Alouatta palliata and A. pigra in southeastern Mexico and Central America with geographic and ecological features to infer current barriers and ecological preferences. Distribution data were obtained from museum specimen localities, study sites, historic records and field surveys and integrated into digital elevation and ecosystem maps using GIS. A. pigra evidently occurs at a number of sites above 2,000 m, where temperatures can even drop below zero on some days of the year, thus indicating a broader ecological tolerance than previously reported. Both species occupy a number of vegetation types and can be found in seasonal and nonseasonal forests. We identified the highland massif of northern Central America and its associated coniferous and subalpine vegetation as a geographic barrier that separates the species. In the past, distribution maps for these species have indicated adjacent contiguous ranges, but we propose that they are largely separated by these mountains. There are two contact zones: a broad area of sympatry north of the highland massif in Mexico and a narrow zone in eastern Guatemala where parapatry is maintained by a river barrier and where only A. pigra occurs in the high elevations and cooler habitats inland. We explore an alternative biogeographic scenario for the split of the two species that accounts for the current distribution and differences in elevation and cold tolerances.

Self-anointing behavior in free-ranging spider monkeys (Ateles geoffroyi) in Mexico.

Abstract: During 250 h of observation, a total of 20 episodes of self-anointing, that is, the application of scent-bearing material onto the body, were recorded in a group of free-ranging Mexican spider monkeys (Ateles geoffroyi). The animals used the leaves of three species of plants (Brongniartia alamosana, Fabaceae; Cecropia obtusifolia, Cecropiaceae; and Apium graveolens, Umbelliferae) two of which have not been reported so far in this context in any New World primate species. The findings that only two males displayed self-anointing, that only the sternal and axillary regions of the body were rubbed with the mix of saliva and plant material, and a lack of correlation between the occurrence of self-anointing and time of day, season of the year, ambient temperature or humidity do not fit the hypothesis that this behavior functions in repelling insects and/or mitigating topical skin infections in this species. Rather, the data and the observation that the leaves of all three plant species spread an intensive and aromatic odor when crushed, support the hypothesis that self-anointing in A. geoffroyi may play a role in the context of social communication, possibly for signaling of social status or to increase sexual attractiveness.

Development of the visual preference of chimpanzees ( Pan troglodytes ) for photographs of primates: effect of social experience

Abstract: In a study by Tanaka (2003) five captive chimpanzees preferred photographs of humans to those of chimpanzees. All the subjects were raised by humans and lived in captivity for many years. This suggests their preference might have developed through social experience. In this study examined this hypothesis by using three young chimpanzees raised by their mothers in a captive chimpanzee community. The young chimpanzees were tested four times before six years of age. I also tested eight adult chimpanzees that had been in captivity for more than 20 years. Each subject was presented with digitized color photographs of different species of primates on a touch-sensitive screen. The subjects received a food reward when they touched a photograph, irrespective of which photograph they touched. All the adult chimpanzees touched photographs of humans more frequently than those of any other species of primate. Two of the young chimpanzees showed no species preference before reaching 5 years of age, when they started to show preference for humans. The remaining young chimpanzee consistently preferred chimpanzees. These results suggest that development of visual preference of chimpanzees is affected by social experience during infancy.

Description of joint movements in human and non-human primate locomotion using Fourier analysis.

Abstract: To describe and help interpret joint movements in various forms of primate locomotion, we explored the use of Fourier analysis to represent changing joint angles as a series of sine and cosine curves added together to approximate the raw angular data. Results are presented for four joints (shoulder, elbow, hip and knee) with emphasis on the shoulder, and for five types of locomotion (catarhine primate quadrupedal walking, human hands-and-feet creeping and hands-and-knees creeping, and human walking and running). Fourier analysis facilitates functional interpretation of the angles of all four joints, by providing average joint angles and an indication of the number of peaks and troughs in the angular data. The description of limb movements also afforded us the opportunity to compare human and other catarhine joint angles, and we interpret the Fourier results in terms of locomotor posture and type. In addition, the shoulder data are useful for determination of some aspects of interlimb coordination. Non-human primates walking quadrupedally and humans creeping on hands and knees generally evince diagonal couplets interlimb coordination, in which the hand on one side strikes the substrate at about the same time as the contralateral foot or knee. Furthermore, human walking and running seem to follow a similar pattern, as indicated by Fourier analysis. From our data it is concluded that human bipedal gaits are qualitatively similar to diagonal couplets gaits in other primates, but quite different from the lateral couplets gaits used by many non-primate mammals. A number of other benefits of Fourier analysis in primate locomotion studies are also discussed. These include the ability to make statistical comparisons among various types of limb movements in a wide variety of species, a simple archival technique for limb movement data, and a greater understanding of the variability of locomotor movements.