Influence of artificial food supply on population parameters and dispersal in the Hakone T troop of Japanese macaques

A free-ranging troop of Japanese monkeys was observed for seven years from April 1971 to March 1978 in the Hakone area, Kanagawa Prefecture, Japan. This troop was fed artificially between 1956 and 1977. The artificial food supply was reduced by about half after 1974. The troop-size fluctuated around 100 between 1971 and 1974, but fell drastically from 91 in 1975 to 58 in 1978. Population parameters were compared between the two periods of 1971–1974 and 1975–1977. Clear differences between the two periods were found in primiparous age, ratio of non-natal resident males to all resident males, ratio of newcomers to non-natal resident males, age-specific disappearance rate, and proportion of deserters observed in the study area. A correlation existed between the number of males and females of 5 or more years of age in the troop. The numbers in the three age-sex groups (natal males, non-natal males, and females of 5 or more years of age in the troop) were closely connected with one another. The scarcity of food supply may have caused not only males but also females to disperse. The drastic decrease in troop-size after 1974 could be based on the disappearance of adult females. The cause of the dispersal of young males and adult females could have been mutual competition among the troop members for food, and that in adult males could have been competition for females.     

Subgrouping Patterns in a Group of Wild <Emphasis Type="Italic">Cebus apella nigritus</Emphasis>

Seasonal patterns of group fragmentation, including the size of subgroups and percentage of time spent in subgroups, may provide information on individual decision-making in response to resource distribution. Age-sex class composition of subgroup membership can offer insights into the social dynamics of the group as a whole. At most field sites, capuchins (Cebus spp.) form stable groups with no evidence of group fragmentation. Here I describe seasonal subgrouping patterns, including proportion of time spent in subgroups, subgroup size, age-sex membership, dyadic fidelity, stability of membership, and the effect of subgrouping on individual foraging efficiency, in a group of wild Cebus apella nigritus. From September 1996 to August 1997 the study group at the Estação Biológica de Caratinga, Brazil divided into 148 different subgroups, on 99 of 194 census days. In contrast to expectations for subgrouping patterns as a response to seasonal distribution of resources, the proportion of days spent in subgroups did not vary significantly by season. Subgroup composition was relatively fluid, with multimale multifemale subgroups the most common throughout the year. Unimale multifemale subgroups were restricted to the wet season; in contrast, all-male subgroups and unimale unifemale subgroups occurred in the dry season. For both males and females, low rank predicted membership in smaller subgroups. For males, but not females, subgrouping coincided with increased foraging efficiency, as measured by increased time spent ingesting food and decreased time spent traveling on days with subgrouping compared to days with the group in a cohesive unit.     

Seasonal Changes in Male Associative Behavior and Subgrouping of Alouatta palliata on an Island

Howler groups are usually spatially cohesive and stable in composition; however, more flexible grouping patterns occur in some social groups. We analyzed the associative and subgrouping patterns of males living in a group with fission-fusion social organization. Based on information from previous studies on Alouatta palliata and other primates and in the current socioecological models, we established initial predictions on the variations in male behavior according to several socioecological factors. We studied associative behavior via scan sampling at 15-min intervals to register the identity of males in the subgroups and the presence and number of receptive females. We calculated an association index that was then transformed into a measure of association strength. We found individual association trends, as well as important seasonal differences in the subgrouping patterns of males. During the dry season the presence of many receptive females resulted in reduced levels of association, and therefore fewer males per subgroup. The scenario changed during the wet season, when males grouped together significantly more and kinship relationships were a major determinant for individual association preferences.     

The study of vocal communication of wild mandrills in Cameroon in relation to their social structure

The vocal repertoire of the mandrill (Mandrillus sphinx), a forest living baboon, is described, and their vocal communication analyzed quantitatively. Although the vocal repertoire of mandrills corresponds well to that of savanna living baboons,Papio, some characteristics differed, such as the development of long-distance calls and differentiation of vocalizations between age-sex classes. Vocal communication within a group was closely related to changes in the spatial distribution of group members, and the two most common vocalizations, crowing and 2PG, appear to function as contact calls. Based on the wide dispersion of food trees, a group of mandrills divided into several feeding groups (subgroups). The two types of contact call were given in different and in some senses complementary contexts, and helped to facilitate and maintain group integration. According to their acoustic structure, these calls are long distance calls. Influenced by the high-level of attenuation of vocalization on the forest floor, the mandrill has developed them as contact calls, instead of using the contact “grunt,” which is common to the savanna living baboons. Comparing the patterns of vocal exchanges of mandrills with those of gelada and hamadryas baboons which have a multi-levelled society, the social structure of the mandrill is discussed. From the analysis of the spatial distribution of vocal emission, a number of clusters of vocalizations were obtained. These clusters correspond to subgroups. The frequent female-female and female-male vocal exchange between subgroups of mandrills suggest that the relationships between subgroups are less closed than between the one-male units of gelada and hamadryas baboons. Furthermore some of these clusters include more than two vocalizing adult males, while in other clusters there are no vocalizing adult males. Thus, the social structure of mandrills is suggested to be multi-male rather than a multilevelled type. The absence of contact calls specific for short distance and the functional replacement of the grunting of all group members by persistent emission of a loud call (2PG) by usually just one adult male suggests that the social structure of mandrills is not exactly equivalent to that of the multimale troop of savanna living baboons. Usually the use of 2PG is monopolized by one adult male travelling in the rear part of the group. Such monopolization of 2PG emission and the pattern of 2PG-2PG or 2PG-roar exchanges by adult males in some cases indicate the existence of strong dominance relationships among adult males, and especially the existence of a leader male within a multi-male group of mandrills.     

Frequency of aggressive behavior and a case of mortal attack in wildMacaca sylvanus in the Middle Atlas region (Morocco)

We observed a mortal attack against an adult female in a wild population ofMacaca sylvanus in the Middle Atlas Cedar forest ecosystem near the town of Azrou, Morocco. This species is generally believed to be the least aggressive in the whole GenusMacaca. We investigated the possible factors responsible for such an extreme case of increased aggression such as: 1) density of population, 2) availability of food rescues, 3) male competition for females. During a twelve month behavioral observation, we compared the hourly agesex class aggression frequency in the population where the mortal attack occurred with another macaque population living in different ecological conditions relative to density, food distribution and distance from human settlements. The pattern of age-sex seasonal distribution of aggression shows that, in the Middle Atlas, the adult female is the age-sex class most involved in aggressions and especially during food shortage and when resources are patchily distributed, as in the case were the mortal attack occurred.     

Inter-male associations in a wild Japanese macaque troop on Yakushima Island,Japan

Adult male association and its annual change were studied in a wild population of Japanese macaques (Macaca fuscata yakui) on Yakushima Island, Japan. Unlike many other Japanese macaque troops, adult troop males frequently maintained proximity and exchanged grooming with one another in both the mating and non-mating seasons, and the dominance relationship rarely appeared in such inter-male associations. The few cases of agonistic interactions occurred mostly when estrous females or food resources were immediately concerned. Although troop males were very intolerant to newly appeared solitary males (new males) during the mating season, close associations were formed between troop males and new males as soon as the mating season terminated. The consort of new males and lower-ranking troop males with estrous females was frequently disturbed, but these males could copulate no less frequently than higher-ranking males. A comparison among macaque species suggests the existence of two forms of inter-male association: (1) the frequent association based on the symmetrical exchange of social behaviors; and (2) the infrequent and asymmetrical association related to the dominance relationship. The form of inter-male association seems to be influenced by whether or not males can keep close associations with females throughout the year.     

Strategies used by bonnet macaques (Macaca radiata) to reduce predation risk while sleeping

Sleep results in a decrease in alertness, which increases an animal’s vulnerability to predation. Therefore, choice of sleeping sites would be predicted to incorporate predator-avoidance strategies. The current study, conducted in two national parks in southern India, examined the behaviors adopted by bonnet macaques (Macaca radiata) to reduce the risk of being preyed upon while sleeping. Bonnet macaques from an urban setting with a low predatory risk were included for comparison. The physical characteristics of the sleeping sites in the forest corresponded with features that were most difficult for predators to access; bonnet macaques selected emergent trees with high boles near human settlements. These trees typically overhung water. Within the canopy, individuals slept in huddled subgroups near the terminal ends of branches, preferentially selecting branches over water. Subgroups were generally composed of members of the same age and sex, which likely promoted social bonding. Adult males and females with infants selected branches higher than members of other age and sex categories. The lateral distances of individuals along branches from the main trunk were similar across demographic categories. The size of a subgroup appeared to be limited by the weight a branch could support; lateral distances were maintained by regulation of mean subgroup weight, with heavier individuals forming smaller subgroups. The urban troop slept on the top of a building. Subgroup compositions at the urban site were similar to those at the forest sites. However, subgroup size, not restricted by branch fragility, resulted in larger subgroups than those found in the forest. Our results indicate that bonnet macaques adopted a suite of behaviors that reduced their risk of being preyed upon at night by selecting sleeping sites that minimized predator encounters and by selecting the safest locations within the canopy.     

Effects of contextual and social variables on contact call production in free-ranging ringtailed lemurs (Lemur catta)

Ringtailed lemurs (Lemur catta)often emit a characteristic vocalization when resting as a troop. This “meow call” is believed to serve an intragroup contact function. I investigated the effects of behavioral context and proximity on call production and acoustic features of the vocalization in a free-ranging troop in the Berenty Reserve, Madagascar. When group members were dispersed, the meow call was given frequently, and the acoustic features of the call probably increased the locatability of the emitter. I evaluated social relationships among the troop members from grooming interactions and spacing data. I also studied the call exchange network among the troop members, the results of which indicate that calls are exchanged between the two subgroups of females, which they connect.     

Environmental and Social Factors Associated with the Occurrence of Stone-Handling Behavior in a Captive Troop of <Emphasis Type="Italic">Macaca fuscata</Emphasis>

Stone-handling, a documented behavioral tradition in Japanese macaques (Macaca fuscata), occurs in both captive and provisioned free-ranging troops. We utilize data systematically collected as part of a broader investigation of stone-handling behavior in a captive troop to elucidate the environmental and social factors responsible for its occurrence. We analyzed contexts of stone-handling over 18 mo to determine under what conditions individuals most often perform it. There is clear seasonal variation in the occurrence of stone-handling. The lowest number and shortest duration of stone-handling bouts were in winter, gradually increasing to a peak in summer, and again decreasing toward autumn. Monkeys stone-handled more on clear sunny days than on cloudy or rainy ones. They displayed the behavior less under stressful conditions caused by human intervention or by aggression among troop members. Such stressful social conditions appeared to decrease individual motivation for stone-handling. In other words, individuals most frequently performed stone-handling under more relaxed environmental and social conditions. The findings are consistent with the hypothesis that stone-handling is a form of solitary object play behavior in macaques.     

Demographic consequences of a food and water shortage to desert Chacma Baboons,Papio ursinus

The age-sex composition of a chacma baboon (Papio ursinus)population changed following a 5-month interval of extreme food and water shortages. Mortality was significantly greater among adult females, juveniles, and infants than among adult males. The probable basis of 19 of 22 deaths during the interval of food and water shortage was starvation caused by drought conditions which localized water sources, reducing access to food resources. This resulted in a long-term (> 6-year) shift in adult sex ratios within this three-troop population, from 1.04 to 1.42-1.58 adult and subadult males per adult female. Patterns of intertroop interaction were also influenced by food scarcity, which determined which troop was most seriously affected.     

Fission-fusion social organization inAteles andPan

Recent research on the ecology and behavior of free-ranging spider monkeys (Ateles paniscus chamek) allows a more detailed comparison with the chimpanzee,Pan troglodytes, than has been possible previously. Despite their distant common ancestry, chimpanzees and spider monkeys share an unusual fission-fusion social system. In this paper, I compare subgroup size and composition, social unit structure, ranging behavior, patterns of philopatry and dispersal, and social relationships in the two taxa. It is proposed that spatial and temporal patchiness in food dispersion and abundance, resulting in a high-level of feeding competition between females within a group, has been the most important ecological selection pressure leading to the evolution of fission-fusion social organization in both species.     

Analysis of population changes by measurement of body weight in the Koshima troop of Japanese monkeys

Measurements of the body weight of monkeys in the Japanese monkey troop on Koshima islet in southern Japan have been made since 1970. Population changes in the troop have been recorded since 1952. The population changes were further analyzed on the basis of the body weight changes of the troop members. The recent history of the Koshima troop can be divided into three periods differing according to conditions of artificial feeding: (1) a semi-wild period (SW Period, 1952–63); (2) an artificial feeding period (AF Period, 1964–71); (3) and a restricted artificial feeding period (Non-AF Period, 1972–77). The AF Period represented a period of population growth, whereas the Non-AF Period was a declining one when the population density of the troop was roughly ten times that of most wild troops. These population changes, i.e., changes in population parameters especially in the population declining phase, could be fairly well understood from the general features of the body weight changes of the troop members, the slow body weight growth, elevation of age at first birth, and small size of adult females. Reproduction and survival were affected by seasonal and yearly changes in body weight. The pattern of changes in body weight displayed seasonal peaks in the autumn and spring. Of these, the former suggests that fruit eating in the autumn is an important factor in the reproduction and growth of the monkeys.     

Interindividual distance and influence of dominance on feeding in a natural Japanese macaque troop

In a natural troop of Japanese macaques (Macaca fuscata yakui), the dominant-subordinate relationship restricted the feeding behavior of the subordinate in two ways: (1) the dominant drives away the subordinate through agonistic interactions; and (2) the subordinate avoids approaching the dominant without any agonistic interactions. These occurred only infrequently, and only when an interindividual distance was less than a certain distance, which is called the “tolerance/intolerance” (T/I) distance. On the other hand, the usual interindividual distance when feeding was much greater than the T/I distance. Therefore dominance has little influence on feeding in the study troop. In the study troop, the T/I distance between kin-related females was shorter than that between unrelated individuals. Although this difference may facilitate kin selection if the troop faces severe competition over concentrated food, the difference does not seem to influence survival or reproductive rate in the study troop.     

How social relationships influence a monkey's choice of feeding sites in the troop of Japanese macaques (Macaca fuscata fuscata) on Koshima islet

When the individual Japanese macaques of the Koshima troop feed on natural food, they usually feed alone. In situations where animals usually feed without other animals, there is a possibility that subordinate animals may avoid feeding sites at which dominant animals are feeding. This paper examines whether social relationships such as kinship or dominance exert any influence on an animal's choice of feeding sites, by analyzing episodes in which an animal approached and climbed into a tree where other animals were. As a result, it was found that social relationships did not influence whether an animal climbed into a tree where other animals were feeding, and that no particular age-sex pair co-fed. Agonistic interactions frequently occurred when the inter-individual distance was less than 1 m. From these findings, the feeding sites were divided into two spaces: (1) a tolerance feeding space, and (2) an intolerance feeding space. It is presumed that animals can feed without entering others' intolerance feeding spaces when food is abundant, as it was in the present study period. Thus social relationships do not influence an animal's choice of feeding sites in such a situation.     

Vocal Communication in a Fission-Fusion Society: Do Spider Monkeys Stay in Touch With Close Associates?

In fission-fusion societies, in which animals from the same group may spend long periods of time apart from each other, individuals could use long-distance vocalizations to maintain contact with others. This could be achieved with vocalizations that simply carried information about the caller's identity and location. I explored this possibility using observations and experiments from a 3-year field study of spider monkeys (Ateles geoffroyi) in Punta Laguna, México, analyzing the use of the species' most frequent vocalization, the whinny. By following 2 subgroups simultaneously, I found that subgroups that were within the active space of the whinny approached each other more often than subgroups that were farther apart. Individual adults in these subgroups also emitted more whinnies when they were within hearing range of another subgroup than when farther apart. I used a paired playback design to determine whether whinnies could influence the behavior of close associates as opposed to nonassociated individuals. Although nonassociates were as likely as close associates to respond vocally to playbacks of whinnies, only a close associate ever approached the speaker. Collectively, the results suggest that whinnies are used by spider monkeys to achieve flexibility in spacing while maintaining specific social relationships.     

Distribution and conservation of the foldback transposable element inDrosophila

Summary Foldback elements are a family of transposable elements described inDrosophila melanogaster. The members of this dispersed repetitive family have terminal inverted repeats that sometimes flank a central region. The inverted repeats of all the family members are homologous.The study of the distribution and conservation of the foldback elements in differentDrosophila species shows that this distribution is different from that of the hybrid dysgenesis systems (PM and IR). Sequences homologous to foldback elements were observed by Southern blots and in situ hybridization in all species of themelanogaster subgroup and in some species of themontium andtakahashii subgroups. The element was probably already present before the radiation of these subgroups. No evidence of horizontal transmission of the foldback element could be observed.     

Social organization of wild talapoin monkeys

A troop of wild talapoins in Cameroon had 70 members including all age-sex classes. Observed between the birth season and the next mating season, it was habitually divided into subgroups. Subgroups most commonly observed were (1) adult and large juvenile males: (2) adult females with infants, small juveniles, and large juvenile females; (3) medium sized juveniles with a single adult male. Adult females and adult males were rarely sighted together and never seen to interact. From observations of caged groups, predictions are made about the changes in this organization which might be expected during the breeding season. A possible parallel with the ecologically similar squirrel monkey is suggested.     

The behavior of white-faced capuchins (Cebus capucinus) at a dry-season waterhole

During a study of white-faced capuchins (Cebus capucinus) in Santa Rosa National Park, northwest Costa Rica, the study troop drank daily from a single terrestrial waterhole for approximately three months during the dry season. The drinking order of troop members at the waterhole was not random: adult males tended to be in the first quartile of the drinking progression, adult females generally occurred with equal frequency throughout the progression, and juveniles drank most commonly in the third quartile. There were also differences in the usual drinking ranks among individuals of the same age-sex class. It is hypothesized that those adult males which are usually first in the progression are increasing their personal fitness by reducing the risk of predation on their offspring and on potential mates. The tendency of adult females to precede juveniles may similarly reflect protection of offspring. The daily visits to the waterhole by the study troop did not appear to greatly restrict the use of their range. It is suggested, however, that the availability of standing sources of water may be an important factor affecting the local distribution and density of capuchins in seasonally and chronically dry areas.     

Ecological and demographic influences on the pattern of association in St. Kitts vervets

A group of St. Kitts vervets (Cercopithecus aethiops) were observed to have an association pattern which involved the formation of spatially separated subgroups which were unstable in composition. Five types of subgroups are described which account for 94% of the associations observed. The size of the subgroups changed when the abundance and distribution of the available resources changed. Based on this observation and on an analysis of the diurnal patterning of subgroups, we suggest that the association pattern of the vervets is a response to the distribution of food resources and that it arose under specific demographic conditions.     

Bipedal behavior of olive baboons (Papio anubis) and its relevance to an understanding of the evolution of human bipedalism

The bipedal behavior of a troop of olive baboons (Papio anubis) is described. Bipedalism is relatively rare but nevertheless occurs in a wide variety of situations, although bipedalism during feeding occurs much more frequently than in other situations. The incidence of bipedalism varies between different age-sex classes and between individuals within age-sex classes. This pattern of bipedalism occurred within an overall adaptive response, particularly in feeding behavior, which was similar to that of the gelada baboon (Theropithecus gelada). The data on bipedalism is used together with an existing model of early hominid differentiation based on T. gelada to indicate the types of bipedal behavior which might have occurred in early hominid small object feeders and to suggest how a bipedal pattern of this type might have served as a basis for the action of selection for a more committedly bipedal pattern at later stages of hominid evolution.