Movement patterns of yellow baboons (Papio cynocephalus): Central positioning of walking infants

According to DeVore and Washburn's protection theory of the spatial organization of moving baboon troops, walking infants, which are among the most vulnerable and least self-sufficient of all troop members, should tend to occupy the troop's center. The protection theory is an ultimate hypothesis from which persistently recurring behavior is expected. Two troops living in Mikumi National Park, Tanzania, were compared with troops studied at other locations. Walking infants tended to occupy the center of their troop and to be underrepresented primarily in the frontal portion of progressions and secondarily in the rear. The lead position of progressions was analyzed using 82 walking infants, 11 troops, three locations, two species, and three studies involving eight or more observers employing somewhat different procedures at the different study sites. Despite so many opportunities for variation, 1,317 observations from these 11 troops did not produce a single instance in which a walking infant led the troop and very few in which one was in the frontal twelfth.     

Movement patterns of yellow baboons (Papio cynocephalus): Sex differences in juvenile development toward adult patterns

Age-sex differences in the sociospatial positioning of progressing baboon troops have been postulated as an important, protective aspect of baboon adaptation to a terrestrial existence. The protection theory is an ultimate hypothesis which can be disproven by showing that the postulated age-sex positioning fails to occur. Alternatively, confidence in the protection theory can be increased if the postulated positioning persists across several troops despite significant opportunities for variation, and if progression order is shown to be linked to biological phenomena such as sex differences in physical maturation. Data from 73 individually identified, free-ranging juveniles of both sexes were compared with previous findings. Small juveniles of several troops were more centrally located than large juveniles. Large juveniles males were more toward the front than were large juvenile females. As male walking infants and juveniles aged, a change in positioning (i.e., location) occurred: males were located increasingly toward the front of progressions. Comparable data from females suggest that the adult female pattern had begun to form among large juveniles. Data are consistent with an ultimate protection theory.     

Progressions of adult male chacma baboons (Papio ursinus) in the moremi wildlife reserve

It has been suggested that the sociospatial organization of baboon progressions has a protective function in which the most physically powerful troop members, the adult males, play a key role. This theory implies regularities in adult male progression order for different species of savannah baboons with similar social systems. Quantitative progression data are available from two such similar baboon species, olive and yellow, but not from the third, chacma. The order of movement of 15 adult male chacma baboons was determined from 40 progressions observed at the Moremi Wildlife Reserve, Botswana. The chacma males were most often found in the front sixth of progressions, next most often in the second sixth, and about equally often from there to the rear. As expected from the protection theory, this frontal positioning is consistent with available quantitative data from other species of savannah baboons.     

The waning of dependence in infant free-ranging yellow baboons (Papio cynocephalus) of Mikumi National Park

Development toward independence during the early years of baboon life is reflected in the infant's transition from riding on its mother to walking on its own during progressions from one location to another. This transition was studied during the first year of life in 55 infants from two differently sized troops living in Mikumi National Park, Tanzania. There was a nearly linear transition in the first year from almost 100% ventral riding to almost 100% walking. The amount of dorsal riding started near zero, reached a plateau lasting from about the 15th to the 26th wk of life, and then gradually declined to zero. Dorsal riding did not replace ventral; rather, dorsal riding increased in frequency until it occurred about as often as ventral riding. Prolonged ventral riding by infants of the smaller of the two troops may have been due to spacing differences or to greater nervousness among members of the smaller troop. There were no significant differences in riding or walking associated with the time of day or the infant's sex. The rate of transition from riding to walking was greatest from about the fifth to the seventh months, which may be especially significant time in the early development of independence.     

New evidence from observations of progressions of mandrills (Mandrillus sphinx): a multilevel or non-nested society?

African papionins are well known for the diversity of their social systems, ranging from multilevel societies based on one-male-multifemale units (OMUs) to non-nested societies. However, the characteristics of Mandrillus societies are still unclear due to difficult observational conditions in the dense forests of central Africa. To elucidate the characteristics of mandrill societies and their social systems, I analysed the age–sex compositions, behaviours, and progression patterns of their horde/subgroups using videos of them crossing open places. The progressions were very cohesive, and the very large aggregations (169–442 individuals) had only 3–6 adult males (1.4–1.8 % of all individuals) and 11–32 subadult males (6.5–7.2 %). No herding behaviours were observed in the males, and most of the small clusters within the progressions were not analogous to the OMUs of a multilevel society but instead consisted of only adult females and immatures. The progressions of alert mandrills showed patterns similar to those observed in a non-nested social system: females with dependent infants were concentrated toward the rear and adult and subadult males toward the front. These results suggest that cohesive aggregations and a female-biased sex ratio are common characteristics of mandrill species. Mandrills may form female-bonded and non-nested societies, although their fission–fusion dynamics may be different from those typical of savannah baboons.     

The variable social organization of hanuman langurs(Presbytis entellus), infanticide,and the monopolization of females

Data from 24 wild populations of hanuman langurs (Presbytis entellus)in south Asia are used to test hypotheses seeking to explain variation in troop structure and the incidence of infanticide. The occurrence of infanticide is associated with a one-male troop structure and not with a high density. The density, predation, and economic-advantage hypotheses, as explanations for the occurrence of one-male and multimale troops, are not supported by the review. However, the monopolization hypothesis is not contradicted; the number of adult males per troop is significantly correlated with troop size and with the number of adult females per troop. Therefore it is suggested that a one-male troop structure will arise if a male is able to monopolize a group of females, a multimale troop if he cannot. One-male troops may predispose to infanticide because of high variance in male mating success and high intermale competition between groups rather than within troops. If female dispersion determines troop structure, it is speculated that females could manipulate males to form a multimale society if the advantages in terms of infant survival and intertroop conflict exceeded the costs in terms of not producing infanticidal “sexy sons.”     

Comparative study of grooming relationships among wild Japanese macaques in Kinkazan A troop and Yakushima M troop

The influences of socionomic sex ratio (SSR; adult males/adult female) and troop size upon male-male, female-female, and male-female grooming relationships were examined and compared between two wild Japanese macaque troops (Kinkazan A and Yakushima M troops) in Japan. The Yakushima M troop was smaller and had a higher-SSR than the Kinkazan A troop. Between the troops, (1) the male-male grooming frequency and number of partners were greater in the Yakushima M troop than in the Kinkazan A troop; (2) the female-female grooming frequency and number of partners were not different; and (3) the male-female grooming frequency and number of partners were not different. Based on these features, the patterns of female-female and male-female grooming relationships appear to be independent of SSR and troop size variations. In contrast, male-male grooming relationships are influenced by both factors, especially SSR. Frequent grooming interactions among males may be useful for the continued coexistence of relatively many males especially in a higher-SSR troop.     

Social interactions among adult male langurs (Presbytis entellus) at Rajaji Wildlife Sanctuary

A population of langurs (Presbytis entellus)at the Rajaji Wildlife Sanctuary in northern India was investigated for 1820 hr throughout a 10-month period in 1978. Data were collected from four bisexual troops and the adult males that ranged outside of bisexual troops. Most (60%) of the observation hours occurred with a main study troop from which social and ecological data were collected. The langur population at Rajaji shows pronounced birth and mating seasons. The population density is high (ca. 80/km ²), with about 75% of the adult males living outside of bisexual troops, which typically are large and multimale. Males outside of bisexual troops occur in small all-male bands or as isolates. Relations between bisexual troops and all-male bands are characterized by relatively low levels of aggression, and members of all-male bands are able to associate with bisexual troops for prolonged periods during the mating season. As a result of these associations, nontroop males are about as successful as troop males in achieving reproductive access to troop females. These associations between bisexual troops and all-male bands occurred with a minimal amount of agonistic behavior and without mortality or injury to troop females or immatures.     

Changes in dominance rank and division of a wild Japanese monkey troop in Arashiyama

This article forms the second report on the Arashiyama troop of Japanese monkeys and concerns a troop division which took place in June, 1966, and various problems of rank and consanguinity which accelerated the division. (1) The hypothesis advanced in the first report has been verified; (2) at the time of troop division, several consanguineal groups formed one unit; (3) among 16 consanguineal groups, those from 1st to 7th in rank joined the A troop, while those from 8th to 16th joined the B troop; (4) dominance relation between the two division troops was B troop>A troop, reflecting the former ranking between the leader males of the two troops; (5) shifting of monkeys from one troop to the other after division occurred frequently, but males began to make their own movements when they attained 4 or 5 years of age and rarely moved together with their mothers or other consanguineous-relatives; (6) monkeys which were continuously in the same troop after division almost always obtained higher ranks than did monkeys who frequently shifted from one troop to the other; (7) after division, some males joined neither of the two division troops but formed a group, a so-called all-male group or male party, and moved about independently.     

Intermale relations and troop male membership changes in langurs (Presbytis entellus) in Nepal

Data on intermale social relations and troop membership changes in one Nepalese high-altitude population of free-ranging langurs (Presbytis entellus)are reported here. Data were collected from six troops by three observers and cover 32 months of observations. The predominantly multi-male troops indicate an alternating pattern of exclusions and introductions with gradual adult male replacement. Takeovers and infant killing were not observed. Analysis of adult social behavior records show qualitative and quantitative differences in intrasexual relations, with primarily agonistic social contacts occurring between males. Agonistic encounters between females and between males differ in frequency of occurrence, types of be-haviors used, cause, and consistency in direction of threats between individuals. Individual adult male frequency of interaction with females and immatures varied significantly, with the majority of these interactions occurring between the dominant troop male and other troop members. Data indicate that intermale dominance is a major factor in determining male access to fertile females: This appears to be achieved by either directly excluding males from the troop or effectively “controlling” their inter-actions with troop females. Data from these studies are compared with data from other Presbytis entellusinvestigations. Review of these data suggests that intraspecific variability in intermale social dynamics and type of troop male membership change are correlated with the percentage of nontroop males. It is suggested that environmental pressures resulting in social crowding can be critical in determing the occurrence of takeovers in some populations of Presbytis entellus.     

Intertroop Transfer and Dominance Rank Structure of Nonnatal Male Japanese Macaques in Yakushima, Japan

We examined the interaction between intertroop transfer and male dominance ranks in a wild population of Japanese macaques (Macaca fuscata yakui) in Yakushima using data collected over 15 years. Intertroop transfer tended to maintain a linear, stable, and age-graded dominance rank order among nonnatal males irrespective of variation in troop size or composition. All males that joined a troop at the top of the rank order were prime adults. Among males joining at lower ranks, entry at the most subordinate position in the hierarchy was common. Males joining at lower ranks tended to join troops in which all other resident males were the same age or older. Adult males tended to join troops with few or no males. Young males tended to join troops with many resident males, and in which a relatively large proportion of males was other young ones. Intertroop transfer was responsible for most rank changes of resident males. The most common cause of males rising in rank was the emigration or death of a higher-ranking male. Males fell in rank most frequently as a result of a new male joining the troop at the top of the hierarchy. Rank reversals among resident males were rare. The cumulative effects of male transfers produce sociodemographic variation within a troop over time and sociodemographic diversity among troops in a local population. A key feature of intertroop diversity is that larger troops have a significantly greater proportion of young males than smaller troops. This diversity also creates the potential for intertroop variation in the severity of male competition and provides a range of options for transferring males.     

Solitary male chacma baboons in a desert canyon

Solitary and paired adult (nine) and subadult (one) male chacma baboons, Papio ursinus, were observed over a period of years living in part of a wooded desert canyon not used by adjacent troops. These extratroop males were silent when alone and gave only one alarm vocalization, the “wa-hoo” call, when paired. The space occupied by them is unsuitable for use by troops according to criteria for adequate sleeping sites and access to water. But the foods available to them, especially figs, but also other fruits and fresh acacia seeds, were abundant. These foods are more highly preferred by baboons than those foods available to troop members. Troop members deplete these resources and shift to less preferred foods with lower water content and longer processing times. All of the adult members of the troop adjacent to these isolated males were infected with a skin disease. Isolated males were not so afflicted and so cannot have originated from, or ever been a part of, this troop. They probably moved to the space where they were observed from other inland troops, traveling to their current home range along the narrow canyon river course.     

Five natural troops of Japanese monkeys on Shodoshima Island: II. A comparison of social structure

The results of a comparative study of five natural troops of Japanese monkeys living on Shodoshima Island are as follows. (1) When troops were feeding at the feeding places, various cases, such as individuals spaced out dispersively or close by in a gregarious state, were observed. (2) Differences were also observed among the troops at the feeding place; some troops always fed in a dispersive state, on the whole, while others fed in a gregarious state with small distances between individuals. (3) Differences of social structure were observed among the five troops: differences of the number of classes and sub-classes in males and females, of the relation between classes and their age distribution in males, of the proportion of individuals who intruded into the central part of the troop or who made it their core area of activity to the total male population, etc., and it was also assumed that some troops were integrated more strictly, while others were integrated loosely. (4) These differences of social structure among the troops were assumed to be closely related to the gregariousness or dispersiveness of the each troop at feeding time. From these facts several decisive factors of social structure were considered.     

Consortship and Mating Success in Chacma Baboons (Papio cynocephalus ursinus)

Chacma baboons (Papio cynocephalus ursinus) show a lower consortship take‐over rate and longer consortship duration than the other savannah baboons ( Bulger 1993 ). It has been argued that researchers have focused on atypically small troops with few adult males, resulting in low competition for access to oestrous females. Consortship data from two mountain baboon troops containing seven and four males, respectively, were analysed to determine whether the troop with the greater number of males showed a weaker correlation between mating success and rank due to an expected higher consortship take‐over rate. No consort take‐overs were observed in either study troop and mating success in both troops was correlated strongly with male rank. The distribution of days spent in consortship amongst the males could be explained by the priority‐of‐access‐model. The degree of cycle overlap determined the number of males observed consorting oestrous females, whereas the number of males did not influence the relationship between rank and consorting activity.     

Some aspects of infanticide and intermale competition among langurs,Presbytis entellus,at Dharwar,India

Conspecific infanticides by male langurs depresses population growth in their densely populated habitats. An infanticidal model developed from demographic parameters obtained in the Dharwar study area predicts an almost stable population. On the other hand, a non-infanticidal model predicts a population growth by 2.6% per year. The effect of frequent troop usurpation and infanticide on the control of population growth must be strong if the natality rate is high. For subadult and juvenile surplus males, it must be difficult to survive and to mature in the all-male party in its poor habitat. However, from calculations for living adult males and the number of troops at Dharwar, most adult males are thought to be able to obtain a troop within five years of first challenge of usurpation. Dominant males do not always take over a troop containing more females than do subordinate males. These simple assessments require further intensive field studies to determine the precise differences between infanticidal and non-infanticidal populations and whether or not dominant males make a greater genetic contribution than subordinate males to subsequent generations.     

The social organization of forest hanuman langurs(Presbytis entellus)

The social organization of hanuman langurs (Presbytis entellus;Colobinae) was studied in Kanha Tiger Reserve, Central Indian Highlands, for 2300 hr (1980–1985), in a mosaic of moist deciduous forest and anthropogenic meadow. The langur population density was 46.15/km ² and the mean troop and band sizes were 21.7 and 14.0, respectively. Of 14 troops, 13 were one-male and 1 was trimale. The population adult sex ratio was 1:2.5. The majority of female sexual solicitations was directed toward the harem male. The birth season was December to May, with an estimated gestation of 171–224 days. A review of langur reproductive seasonality suggests that breeding throughout the year is confined to those populations able to exploit human food sources. Mortality during the first year of life was 40%, including infanticide. A significant positive correlation was found between the age of an infant at death or disappearance and the mother’s subsequent interbirth interval. Five cases of social change are described, including female transfer, one-male to multimale change, troop formation, and gradual and rapid replacement of troop males. Takeover-associated infant killing by band males, in an undisturbed moderate-density population, supported the sexual-selection/infanticide hypothesis but not the social-pathology hypothesis. However, it could not be directly confirmed that an invading infanticidal male gains a reproductive advantage. The male tenure of harems was estimated to be 45 months.     

Secondary sex ratio and maternal dominance rank among wild yellow baboons (Papio cynocephalus) of Mikumi National Park,Tanzania

The Trivers and Willard model predicts that offspring of dominant mothers will be biased toward males and offspring of subordinate mothers towards females, whereas a local-resource-competition hypothesis predicts the reverse. Available data bearing upon these alternative predictions are inconsistent. It has been suggested that the local-resource-competition hypothesis will predominate when resources are scarce, and the Trivers-Willard hypothesis when resources are abundant. The relationship between maternal dominance and secondary sex ratio for 214 offspring of 61 females was examined using four troops of wild yellow baboons living in Mikumi National Park, where the population was increasing in a resource-rich habitat. For all troops combined, no significant relationship was found between offspring sex ratio and maternal rank. The four troops separately showed inconsistent trends, and in no case did the relationship reach conventional levels of statistical significance. In contrast, the local resource-competition hypothesis was supported by a study of yellow baboons done with one troop and 80 offspring in Amboseli National Park, where a massive population decline had occurred. The contrasting Amboseli and Mikumi results may be due to differences in resource-competition at the two study sites, or to stochastic variation. © 1992 Wiley-Liss, Inc.     

Population organization of wild pig-tailed macaques (Macaca nemestrina nemestrina) in West Sumatra

A field study on wild pig-tailed macaques was conducted in West Sumatra, Indonesia, during three periods from January 1985 to February 1987. During the nine months of the first two periods, unprovisioned monkeys were traced and observed. During the eight months of the last period, monkeys were provisioned and observed mainly at baiting sites. Three troops and ten solitary males appeared at the two baiting sites. Some males immigrated into and emigrated from the troops. The troops had a multi-male multi-female composition. The size of the various troops was 74, 49, and 81 individuals, respectively, and the mean adult sex ratio in the troops was 1:6.3; that is, markedly biased towards females. The home ranges of two of the troops overlapped considerably. When the troops encountered each other at the baiting sites, a clear dominance relationship was recognized. The troops differed in their integration as ranging units: two of the troops did not form subgroups (temporary fission and fusion of each troop), while the other troop frequently split into subgroups. Recent field studies on pig-tailed macaques have suggested a multi-leveled society with harem-type unit groups. However, in the present study, the troops observed had neither a substructure similar to harem-type groups nor a superstructure that emerged as a result of fusion of the troops. The unit group of the pig-tailed macaques appears to be a multi-male, matrilineal group.     

Long distance mobility of male Japanese macaques evidenced by mitochondrial DNA

A 487-nucleotide sequence in the polymorphic D-loop region of matrilineally inherited mitochondrial DNA was compared in samples from 14 (9 adult males and 5 females or young) Japanese macaques (Macaca fuscata fuscata) of two troops at Gagyusan in Takahashi City, Okayama Prefecture, Japan. The majority (7 out of the sampled 9) of the adult males associated with the troops had nucleotide sequences of six distinct types, all of which were different from that of the Gagyusan troop females, whereas two young solitary males shared the same sequence. The present study exemplified a case in which the majority of adult males immigrated from outside the local population. Notably, two of the males were revealed to share the same sequence determined for a matriline 45 km away. Electronic Publication