The order of movement of yellow baboons (Papio cynocephalus).

The spatial organization of progressing baboons is thought to serve a protective function considered important in their adaptation to a terrestrial existence. Progression positions of identified black infants, adult males, and other yellow baboons were determined from repeated samples of troop movements. Spatial positioning by demographic class was similar to that previously found for three troops of anubis baboons living in two different habitats. Such consistency across species and habitats seems unlikely unless it arises from a common genetic background or common ontogenetic stabilizing mechanism.     

Intragroup Social Relationships of Male Alouatta palliata on Barro Colorado Island,Republic of Panama

We examined social and spatial relations of adult males in one group of mantled howling monkeys (Alouatta palliata) on Barro Colorado Island (BCI) in central Panama to document patterns of association. Beyond the existence of an alpha male, we could not distinguish any linear dominance hierarchy among the 6 study males. All males copulated with estrous females. Our findings contrast with reports of intragroup male behavior in Costa Rican howlers. Study males engaged in little or no affiliative or agonistic behavior with one another, but engaged in significantly more such interactions with females. The alpha male, the oldest male and a younger male were most frequently in association with females. Of group males, the oldest male associated significantly more with other males. Overall, male behavior in mantled howling monkeys on BCI generally followed the van Hooff and van Schaik (1994) model of male relationships. The low incidence of intragroup social interactions of any type in the focal males may reflect the energetic costs of social behavior. We suggest that intragroup social relationships among mantled howler males are structured by more subtle means than overt physical interactions, possibly including vocal communication, relationships with individual group females, and kinship.     

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.     

Population structure of olive baboons (Papio anubis (J. P. Fischer)) in the Laikipia District of Kenya

A study of the population structure of olive baboons {Papio anubis (J. P. Fischer)) was conducted near Rumuruti and Nanyuki in the Laikipia District of Kenya during 1969. The overall male: female ratio was 96:100 for all animals captured. The sex ratio of immature baboons favoured males, while adult females outnumbered adult males. Male baboons demonstrated an increased mortality during the juvenile stage primarily due to exploratory behaviour. Female baboons demonstrated an increased mortality incurred during the first pregnancy or birth early in the adult stage. About 50 % of adult females had an infant offspring, while about 75% had a juvenile offspring. Adult female baboons in their native environment produce an offspring every 2.5-3.0 years. No birth peak was discernable and births occurred throughout the year.     

Effects of group composition on agonistic behavior of captive pigtail macaques,Macaca nemestrina

We surveyed agonistic behaviors of 20 captive groups of pigtail macaques (Macaca nemestrina) housed under identical spatial conditions. Fifteen groups contained one male each; the other five groups contained no adult males. Groups included six to twelve adult females, some of which had infants with them. We found no relationship between social density of groups and incidence of agonistic behavior, but significantly more contact aggression (grab, hit, push, bite) and noncontact aggression (chase, open-mouth “threat,” bark vocalization) occurred among females in groups containing no males than in those containing one male each. Apparently, males played an important role in the inhibition of intragroup conflict. We also found that females in groups containing males exhibited less noncontact aggression if infants were present than if no infants resided in their groups. Thus, competition of females over infants must not have been an important constituent of intragroup conflict under the conditions of this survey.     

Anatomically orthogonal QRS electrocardiogram of the baboon (Papio hamadryas) and the macaque (Macaca mulatta). Sex and species differences.

Peak amplitudes of the QRS complex were evaluated in 28 adult macaques (Macaca mulatta) and 28 adult baboons (Papio hamadryas), using two anatomically orthogonal lead systems. The anteroposterior (z) and the transversal (x) component of the cardiac electric field was smaller in females than in males. Comparison of QRS amplitudes in baboons and macaques indicates that the loop of the spatial vectorcardiogram is situated further ventrally and to the right in the former. The relationship between ventrally and dorsally oriented cardiac vectors, in both baboons and macaques, displays a prevalence of ventrally oriented vectors compared with man, in whom this type of relationship is normally not found after the second year of life.     

The comparative psychology of primates]

The comparative study of cognitive activity of primates was carried out during individual and group training. In macaques, capuchins, and chimpanzees was studied the function of abstraction during the recognition of complex visual images and the transition from 2-dimensional plane images to 3-dimensional volume objects. Common features and distinctions were revealed for intellectual characteristics of different species of primates. The formation of intragroup competitive behaviour was observed in marmosets, macaques, and baboons in the process of training.     

Teeth emergence in wild olive baboons in Kenya and formulation of a dental schedule for aging wild baboon populations

Teeth emergence schedules are presented from analysis of 95 wild olive baboons Papio anubis (age range 2–120 months) and compared to recently published results for wild and captive yellow baboons (P. cynocephalus; Phillips-Conroy and Jolly: American Journal of Primatology 15:17–29, 1988). Age at emergence of M1 (20.5 months males, 19.5 months females), I1 (32.5 and 33.5 months) and I2 (40.0 and 39 months) of olive baboons was earlier than in the wild yellow baboons and similar to captive yellow baboons. However, the later emerging teeth were delayed considerably relative to the captive animals and were similar in age of emergence to those of wild yellow baboons. Considerable variation in age of emergence occurred in the later emerging teeth especially among males. Regression analysis of dental scores with age demonstrated differences between olive baboons and captive yellow baboons but not between olive baboons and wild yellow baboons. Combined data on dental scores for wild yellow, olive, and hamadryas baboons provide schedules of AGE (months) = {SCORE – 11.79} ÷ 0.4405 and AGE (months) = {SCORE – 11.24} ÷ 0.4797 for males and females, respectively, which may be used for aging wild baboons. Full permanent dentition in wild baboons is predicted to occur over 1 year later than in captive animals.     

Intergroup affiliative interactions and intergroup transfer of young male Japanese macaques (Macaca fuscata)

The social interactions between young male Japanese macaques (Macaca fuscata) and members of two adjacent groups were studied. Young males usually associated with members of a single group. Although some young males occasionally interacted with members of the neighboring group, the frequency of their intergroup affiliative interactions was much lower than that of their intragroup interactions. The intergroup affiliative interactions were less symmetrical than the intragroup interactions. Three- or four-year-old males who remained in their natal group interacted with males of the neighboring group, whereas males over 5 years old did not. Young males revealed a dramatic change in their association partners from males in one group to those in another during the course of their intergroup transfer. Males who remained in their natal group did not attempt to interact with females of the neighboring group. In contrast, males who had transferred to a non-natal group interacted with females in their natal group. It is suggested that intergroup affiliative interactions and intergroup transfer of young male macaques are influenced by close associations between males. The immediate motivation for transfer of young natal macaques may be some attraction to males outside their group rather than sexual attraction to unfamiliar females.     

Age at maturity in wild baboons: genetic, environmental and demographic influences

The timing of early life-history events, such as sexual maturation and first reproduction, can greatly influence variation in individual fitness. In this study, we analysed possible sources of variation underlying different measures of age at social and physical maturation in wild baboons in the Amboseli basin, Kenya. The Amboseli baboons are a natural population primarily comprised of yellow baboons (Papio cynocephalus) that occasionally hybridize with anubis baboons (Papio anubis) from outside the basin. We found that males and females differed in the extent to which various factors influenced their maturation. Surprisingly, we found that male maturation was most strongly related to the proportion of anubis ancestry revealed by their microsatellite genotypes: hybrid males matured earlier than yellow males. In contrast, although hybrid females reached menarche slightly earlier than yellow females, maternal rank and the presence of maternal relatives had the largest effects on female maturation, followed by more modest effects of group size and rainfall. Our results indicate that a complex combination of demographic, genetic, environmental, and maternal effects contribute to variation in the timing of these life-history milestones.     

Ecology and sociality in a multilevel society: ecological determinants of spatial cohesion in hamadryas baboons

The multilevel society of hamadryas baboons, consisting of troops, bands, clans, and one-male units (OMUs), is commonly perceived to be an effective means of adapting to variable food availability while allowing spatial cohesion in response to predator pressure. The relationship between these variables, however, has never been tested quantitatively. The Filoha site in Awash National Park, Ethiopia is ideally suited to such an investigation as it contains nutrient-dense palm forests in addition to the Acacia scrublands typical of hamadryas distribution elsewhere, allowing comparisons of spatial cohesion across habitat types. Here, we use observations over a 1-year period to examine the relationship between resource availability, perceived predator pressure, and spatial cohesion in a band of wild hamadryas baboons at Filoha. Our results demonstrate that the band was more likely to break into OMUs when foraging in habitats with lower food availability, and that the band fissioned into independent clans more often when preferred resources were not available. Furthermore, the baboons remained in larger aggregations for longer periods of time (i.e., prior to embarking on their daily foraging route) on mornings after predators were heard in the vicinity, and increased cohesion in response to encounters with people who may have been perceived as predators. These results support the notion that hamadryas baboons change their social groupings in response to both food availability and predation risk and that the ability of hamadryas bands to cleave and coalesce in response to changes in these factors underlies the evolution of the hamadryas modular social structure.     

Male rank and reproductive activity in Savanna baboons

Access to sexually receptive baboon females has been linked to male dominance rank. An intensive 19-month field study of mate choice and mate competition among savanna baboons was undertaken in order to elucidate those factors influencing mating success. During this study, male agonistic rank was not correlated with male mating success among adult males. However, the inclusion of adolescent males into the analysis yielded significant correlations between rank and mating success. Examination of prior fieldwork revealed that no baboon field study has conclusively demonstrated a significant correlation between male rank and reproduction among adult males. Most studies reporting a correlation between male rank and reproduction have included subadult males in the analysis. It is concluded that male rank is an unreliable predictor of male reproductive activity among adult male baboons. A low agonistic rank need not reduce male mating success because adult male baboons utilize a variety of reproductive tactics in gaining access to consort females.     

A comparative analysis of subgroup structure and spatial relationships in captive baboons and squirrel monkeys

Subgroup structure, spacing patterns, and the relationship between spatial and behavioral interations were compared for captive baboons and squirrel monkeys. Analysis of the structure, intensity, and permanence of subgroups revealed that the baboons formed low intensity, overlapping subgroups which were relatively flexible while the squirrel monkeys segregated into permanent, high intensity, mutually exclusive cliques. Clique associations and social proximity relationships were found to be better predictors than dominance rank of the nature and frequency of behavioral interactions in the two colonies.     

Life history of hamadryas baboons: Physical development,infant mortality,reproductive parameters and family relationships

Demographic and life history parameters were estimated for a band of free-ranging hamadryas baboons, observed for 5.5 years in Ethiopia. Age-related changes in body weight and dentition were found to be delayed relative to laboratory-reared baboons. On the average, females reached menarche at 4.3 years of age and had their first infant at the age of 6.1 years. The mean interbirth interval was 24 months if the infant survived this period. The survival of infants and juveniles was higher compared to Amboseli yellow baboons, but somewhat lower than in gelada baboons in the Simen Mountains. Males acquired their first juvenile or adult female at the age of 8.5 to 11 years. Male-female pair-bonds lasted several years in most cases. The Cone Rock baboons were organized in a four-level social structure. The troop could split into bands, bands were divided into clans, and clans into one-male units with bachelor followers. The exchange of individuals between social units predominantly occurred within the band. All males of known origin became adult members of their presumed natal clan. Most females transferred also within clans, and juvenile females tended to remain in their natal clan. Females lost by one male to several rivals tended to reassemble in the same new one-male units later on.     

Population genetic insights into the social organization of Guinea baboons (Papio papio): Evidence for female‐biased dispersal

Sex differences in philopatry and dispersal have important consequences on the genetic structure of populations, social groups, and social relationships within groups. Among mammals, male dispersal and female philopatry are most common and closely related taxa typically exhibit similar dispersal patterns. However, among four well‐studied species of baboons, only hamadryas baboons exhibit female dispersal, thus differing from their congenerics, which show female philopatry and close‐knit female social relationships. Until recently, knowledge of the Guinea baboon social system and dispersal pattern remained sparse. Previous observations suggested that the high degree of tolerance observed among male Guinea baboons could be due to kinship. This led us to hypothesize that this species exhibits male philopatry and female dispersal, conforming to the hamadryas pattern. We genotyped 165 individuals from five localities in the Niokolo‐Koba National Park, Senegal, at 14 autosomal microsatellite loci and sequenced a fragment of the mitochondrial hypervariable region I (HVRI) of 55 individuals. We found evidence for higher population structuring in males than in females, as expected if males are the more philopatric sex. A comparison of relatedness between male–male and female–female dyads within and among communities did not yield conclusive results. HVRI diversity within communities was high and did not differ between the sexes, also suggesting female gene flow. Our study is the first comprehensive analysis of the genetic population structure in Guinea baboons and provides evidence for female‐biased dispersal in this species. In conjunction with their multilevel social organization, this finding parallels the observations for human hunter‐gatherers and strengthens baboons as an intriguing model to elucidate the processes that shaped the highly cooperative societies of Homo. Am. J. Primatol. 77:878–889, 2015. © 2015 The Authors. American Journal of Primatology Published by Wiley Periodicals Inc.     

Male investment under changing conditions among chacma baboons at Suikerbosrand.

Male investment in infant baboons was measured by frequency of carrying from 1978 through 1985. A series of hypotheses was generated and tested with the carrying data, based on the assumptions that: male baboons have some capacity to estimate likelihood of paternity; where paternity probability is greater, males will invest more, where potential benefits to males or infants are higher, males will invest more. Carrying was affected by probability of paternity, availability of estrous females, season of conception and season of carrying, infant age, subtrooping, and predation risk. Infants were carried by probable fathers, siblings, mothers' siblings, and unrelated "suitors." Male investment increased female reproductive fitness: carried infants were more likely to survive, and mothers of carried infants had shorter interbirth intervals. Males appeared to estimate paternity both by observed copulations by other males and by the likelihood that copulations could have occurred without being observed. Male care of infant baboons may also be affected by female choice among males, the distribution of probable infants in time, male tenure at alpha rank, the number of males per troop, the probability of infanticide, and energy demands. Subtrooping seems to be historically crucial, by initially creating a situation in which some males have high paternity certainty.     

The fourth level of social structure in a multi‐level society: ecological and social functions of clans in hamadryas baboons

Hamadryas baboons are known for their complex, multi‐level social structure consisting of troops, bands, and one‐male units (OMUs) [Kummer, 1968. Social organization of hamadryas baboons. Chicago: The University of Chicago Press. 189p]. Abegglen [1984. On socialization in hamadryas baboons: a field study. Lewisburg, PA: Bucknell University Press. 207p.] observed a fourth level of social structure comprising several OMUs that rested near one another on sleeping cliffs, traveled most closely together during daily foraging, and sometimes traveled as subgroups independently from the rest of the band. Abegglen called these associations “clans” and suggested that they consisted of related males. Here we confirm the existence of clans in a second wild hamadryas population, a band of about 200 baboons at the Filoha site in lowland Ethiopia. During all‐day follows from December 1997 through September 1998 and March 2005 through February 2006, data were collected on activity patterns, social interactions, nearest neighbors, band fissions, and takeovers. Association indices were computed for each dyad of leader males, and results of cluster analyses indicated that in each of the two observation periods this band comprised two large clans ranging in size from 7 to 13 OMUs. All band fissions occurred along clan lines, and most takeovers involved the transfer of females within the same clan. Our results support the notion that clans provide an additional level of flexibility to deal with the sparse distribution of resources in hamadryas habitats. The large clan sizes at Filoha may simply be the largest size that the band can split into and still obtain enough food during periods of food scarcity. Our results also suggest that both male and female relationships play a role in the social cohesion of clans and that males exchange females within clans but not between them. Am. J. Primatol. 71:948–955, 2009. © 2009 Wiley‐Liss, Inc.     

The Function of Howling in the Ring-Tailed Lemur (Lemur catta)

Long calls are sex-specific vocalizations used for mate attraction or mate defense in many animal species. Ring-tailed lemurs (Lemur catta), female-dominant strepsirrhines, have a male-specific long call termed a howl, with proposed functions that have never been empirically tested. I aimed to investigate why ring-tailed lemur males howl and to test whether the mate defense and mate attraction hypotheses for long-calling were applicable to this species. From March to July 2010, I collected 600 h of focal data on 25 males aged ≥3 year at Beza Mahafaly Special Reserve, Madagascar. I observed each male continuously for 30 min at a time and noted all agonism using one–zero sampling at 2.5-min intervals. I calculated male dominance rank from these data. I recorded days when female estrus occurred and noted howling and intergroup encounters using all-occurrences sampling. Howling rate was not significantly related to female estrus or male dominance rank, providing no support for the mate attraction hypothesis or the intragroup mate defense hypothesis. In contrast, the intergroup mate defense hypothesis was strongly supported. During intergroup encounters, male howling rate significantly increased compared to howling rate at times without other groups present, and a greater number of males participated in multimale howling choruses when compared to times without nongroup members present. My results suggest that male ring-tailed lemurs howl to advertise their presence and location to other groups, but not to male or female members of their own group. Howling could discourage male immigration by advertising the number of males already present in a group. Long calls are used for similar mate defense purposes during intergroup encounters by other primates, including Thomas langurs (Presbytis thomasi) and chacma baboons (Papio ursinus).     

Experimental evidence for limited vocal recognition in a wild primate: implications for the social complexity hypothesis

Although monitoring social information is a key aspect of the social complexity hypothesis, surprisingly little work has compared social knowledge across different species of wild animals. In the present study, I use playback experiments to test for individual recognition in wild male geladas (Theropithecus gelada) to compare with published accounts of social knowledge in chacma baboons (Papio ursinus). Geladas and baboons are closely related primates living in socially complex groups that differ dramatically in group size—geladas routinely associate with more than 10 times the number of conspecifics than do baboons. Using grunts from non-rival males to simulate approaches, I examined the strength of a subject male''s response when the ‘approach’ was from the direction of (i) non-rival males (control), or (ii) rival males (a more salient stimulus if playback grunts are not recognized by the subject). I compared responses separately based on the degree of social overlap between the caller and the subject. Responses indicate that male geladas, unlike baboons, do not use vocalizations to recognize all of the individuals they regularly encounter. This represents, to my knowledge, the first documented evidence of ‘missing’ social knowledge in a natural primate population. The sharp distinction between baboons and geladas suggests that geladas are either unable or unmotivated to keep track of the individual identity of other males in their multi-level society—even males with whom they have a large degree of social overlap. Thus, these results are consistent with the central assumption of the social complexity hypothesis that social cognition is costly.