Infanticide in gelada baboons (Theropithecus gelada)

In a captive group of geladas three cases of infanticide have been observed after replacement of the harem-leader. Two of the infants were born before the replacement, the third one 12 weeks afterwards. The possible function of infanticide is discussed. Female counterstrategies other than avoiding contact with the male were not observed.     

Coalitions among gelada baboons

Geladas spend an unusually large amount of time in quiet, mutual grooming in this captive sample, part of which is presumably due to the effects of captivity and part is a reflection of the gelada pattern of social interactions. The most frequent signals associated with threat or displacement (lid) occurs only at a rate of 5.3 times per hour. Herding and displacement activities are important, but infrequent.One-male bisexual units are extremely cohesive. A male does not tolerate the positioning of another male between himself and any of his females, and the adults of the groups react antagonistically to each other's proximity.The solitary male is not groomed by other adults, but stays withChief's group and backsChief in interactions with the other group.Chief's group is a two-male unit in some ways, but withDemon being excluded from any activity or location which interferes withChief's interactions with his group.The females inEcho's group exhibit a dominance hierarchy, as measured in displacement, or denial of desirable social space. Interactions between individuals ofEcho's group reflect strong preferences between individuals, prohibitions toward certain relationships by more dominant individuals, and the ability to enlist the support of others in coalitions. Coalitions are simply another expression of social relationships that are more frequently expressed in grooming, proximity, and displacement.     

The integration of an adult female gelada baboon (Theropithecus gelada)

An adult female gelada baboon has been integrated into an old-established group in the zoo in Rheine, West Germany. The integration took place in three steps: sight-contact, hourly meetings with the group, continuous stay in the group. Both the agonistic and the social-positive behaviour have been observed between the new female and the group-members. The integration was very difficult and lasted more than six months. The female was not really accepted, before she had not presented to the most dominant female of the one-male unit she has joined. This presenting only took place during the last part of the observations. In contrast to the adult female, the integration of juveniles occurred very quickly and nearly without any problems.     

The reproductive cycle of the gelada baboon

Changes in the visual appearance of the sexual skins of female Theropithecus gelada associated with different stages of the reproductive cycle and with age are analysed using data from a large sample of females in the wild. Changes associated with the oestrous cycle and with pregnancy and birth are confirmed by a more detailed study of particular individuals. These signals are compared with those reported for other primate species. The behaviour of females during the course of the oestrous cycle is examined and compared with that reported for other species of Papio baboons.     

Anti-predator behavior of gelada baboons

The anti-predator behavior of gelada baboons has been observed to consist of simple flight (i.e. they flee to cliffs after becoming alarmed by potential predators). However, active antipredator behavior was observed in a recently found gelada population in Arsi, Ethiopia. This population showed frequent active counter-attacks and severe mobbing at predators. Males fought domestic dogs on the plain and exhibited a systematic mobbing behavior towards a leopard on the cliff face to chase it off. These active anti-predator behaviors are the first confirmed reports on gelada baboons and may provide a useful insight for the understanding of the process of evolutionary adaptation to highland habitats by gelada baboons, as well as for the origin of this small southern population.     

Vocalizations of adult gelada baboons (Theropithecus gelada): acoustic structure and behavioural context

Vocalizations and accompanying behaviors of adult gelada baboons were studied in four one-male groups kept in large outdoor enclosures in the zoos of Stuttgart and Rheine. Twenty-two acoustically different vocal patterns were determined. According to behavioural context, they were grouped into two categories: (1) contact calls and (2) aggressive and defensive calls. Frequency of calling and the production of different vocalizations were related to social rank and to the age of the sender. Vocalizations in species of the closely related genera Papio and Macaca are compared and their evolution is discussed.     

A model of the gelada socio-ecological system

Data from three populations of gelada baboons are used to generate a model of the species' socio-ecology that relates time budget requirements to group size, day journey length, and relevant environmental parameters. The model is used to examine the range of environmental conditions under which gelada could survive. This analysis indicates that a grazing primate like the gelada would run out of available time for foraging at just above and just below the altitudes at which they are now found. This suggests that, contrary to previous supposition, gelada were not driven into a retreat habitat by more competitivePapio baboons, but rather withdrew from lower altitude habitats because they could not survive under these conditions as the climate deteriorated during the Holocene.     

Patterns of reconciliation among captive gelada baboons (Theropithecus gelada): A brief report

Animals that live in groups are frequently exposed to conflict situations and must in some way maintain group cohesion. One mechanism that appears to restore social relationships after they have been disrupted by conflict isreconciliation. This study investigated reconciliatory behavior in the gelada baboon,Theropithecus gelada. The subjects were 11 adult geladas, housed in a large outdoor enclosure at the Bronx Zoo/Wildlife Conservation Park, New York. Five-minute focal animal samples following spontaneous aggression were compared with 5-min matched-control samples. The results of this study were: (1) geladas reunited in a friendly way after aggression; (2) former opponents were attracted to one another rather than dispersed from one another after a conflict; (3) most post-conflict reunions occurred within the first 2 min of the post-conflict period; and (4) geladas do not have any specific types of behavior associated with post-conflict reunions as do chimpanzees and macaques. The results of this study support the hypothesis that gelada baboons reconcile after aggression.     

Adaptation to grass-eating in gelada baboons

Gelada faecal samples were analyzed for nutritional content and for particle size, and compared with similar data forPapio baboons, cattle, and zebra. Particle size in gelada is similar to that for zebra, larger than that for cattle and smaller than that for baboons. Gelada and baboons are less efficient than ungulates at extracting protein from their diet. The data on energy extraction are less easy to interpret and appear to be confounded by dietary and seasonal factors. It is suggested that gelada may be too large to compete effectively with ruminants in low altitude grassland habitats under the climatic conditions that have prevailed in eastern Africa since the late Pleistocene.     

The structure of social behaviour inTheropithecus gelada

Through the use of principal components analysis of the correlation matrix between excentricity quotients of intra- and inter-individual transitions between pairs of the 22 most frequent behaviour elements of male and female gelada baboons observed in captivity, the total variance could be described in terms of a low number of causal factors. In intra-individual sequences the five factors requested of the analysis explain 74 per cent of the total variance. The following intra-individual groupings were found: (I) “autostimulation”, (II) “intensive social” versus “groom”, (III) “male sexual”, (IV) “attack” versus “sexual presentation”, and (V) “greeting” versus “threat”. In inter-individual transitions, the five factors explain 68 per cent of the variance. The following communicative sets were found: (1) “female-sexual releasing”, (2) “greeting and approaching releasing” versus “groom releasing”, (3) “austostimulation releasing” versus “male-sexual releasing”, (4) “fight releasing”, and (5) “conflict”. Mimetic induction of same acts or acts within one particular intra-individual set was frequent.     

The synchronization of voices by gelada monkeys

Evidence is presented from recordings made from captive gelada monkeys (Theropithecus gelada) that these monkeys are capable of synchronizing the onsets of their own vocal sounds to the anticipated onsets of sounds produced by other gelada voices. The possibility is discussed that in order to synchronize the onsets of their own sounds to the anticipated onsets of sounds made by other voices, such gelada voices have to possess the ability to “figure out” the tempo and rhythm of the vocal strings produced by the other voices and precisely control the timing of their own voices. It is suggested that geladas do synchronize their voices by using precise temporal and rhythmical controls on the outputs of their voices that are analogous to the temporal and rhythmical abilities humans use in many of the supra-segmental aspects of speech.     

Periodic changes in the bare skin areas ofTheropithecus gelada

Daily examination of five adult female gelada baboons (Theropithecus gelada) exhibiting menstruation discharges showed noncyclic changes in the coloration of the bare areas of skin in throat, chest, and pubic areas. The intensity of red color in these areas were, on the other hand, markedly affected by the social context (bouts of threats or fights generally heighten the intensity of red) and by sickness or injury (generally lessening color intensity).The features showing most marked cyclic variations were color and degree of swellings of the cutaneous vesicles present around the chest and ventral patches, the intensity of both increasing in the middle of the menstrual cycle and descending as menstruation approaches, to gain intensity again a few days after cessation of the discharges. Of these two features vesicle color appears to be more sensitive to the hormonal changes underlying the variations.     

Blood groups of apes and monkeys. VII. The human-type A-B-H factors in gelada monkeys (Therapithecus gelada)

A series of 21 gelada monkeys (Theropithecus gelada) all showed strong reactivity of their saliva for H substance, but no reactivity for either A or B. Tests on their sera in no case showed the simultaneous presence of both the agglutinins anti-A and anti-B; instead some animals had only anti-A, others had only anti-B, while the remainder had neither anti-A nor anti-B. These findings distinguish gelada monkeys from all other species of Old World monkeys tested to date. They also provide further evidence supporting the genetic independence of the H substance and the A-B-O blood groups.     

Blood protein variation of a new population of gelada baboons (Theoropithecus gelada), in the Southern Rift Valley, Arsi Region, Ethiopia

Blood protein polymorphism of gelada baboon (Theropithecus gelada) to the south of the Rift Valley, Arsi Region, were examined for 36 genetic loci using three electrophoresis techniques for 48 blood samples from three localities, and compared with the northern geladas. New variant alleles and genetic markers of Hb-α, PA-2, and TBPA loci were detected. The distribution patterns of the variant alleles of Hb-α, PA-2, TBPA, Pi, Gc, PGM-II, and TBPA loci were localized in the geographic regions of south and north gelada populations, respectively. Genetic variability of southern geladas was estimated as P_poly=0.083 and , which was comparable to northern geladas. A remarkably high genetic differentiation between the two geographic populations was shown byNei's genetic distance=0.071 and G_ST value=0.420. Our results of genetic analysis suggest that the southern and northern gelada populations have been separated for several hundred thousand years, and gene flow between the two geographic populations is severely restricted. The southern gelada baboon may be regarded as a distinct subspecies.     

On hybridization between Theropithecus gelada and Papio anubis in the wild

Evidence is presented which suggests that Theropithecus gelada and Papio anubis may interbreed in the wild. The behavioural and ecological circumstances which give rise to this are discussed. The implications of these observations to the taxonomic status of these genera are assessed.     

Forage quality and the costs of lactation for female gelada baboons

Field studies of two species of baboons suggest that Altmann's model of maternal time budgets (1980, Baboon Mothers and Infants, Cambridge, Massachusetts: Harvard University Press) provides a good qualitative but a poor quantitative fit to observed changes in the time that mothers spend feeding across infant age. We suggest that the poor quantitative fit might be explained by the fact that food quality varies across time, so that females are forced to feed for longer to gain the same nutrient intake when quality is poor. The hypothesis was tested with data from both gelada baboons,Theropithecus gelada , and Altmann's own baboons, Papio cynocephalus, with rainfall and ambient temperature as indices of vegetation nutritional quality. The results confirm that a three-factor model incorporating infant age, rainfall in the 2 preceding months and current ambient temperature provides a significantly improved fit to the observed data. Copyright 2002 The Association for the Study of Animal Behaviour. Published by Elsevier Science Ltd. All rights reserved.     

Leopard predation on gelada monkeys at Guassa,Ethiopia

Predation is widely believed to exert strong selective pressure on primate behavior and ecology but is difficult to study and rarely observed. In this study, we describe seven encounters between lone wild leopards (Panthera pardus) and herds of geladas (Theropithecus gelada) over a 6-year period in an intact Afroalpine grassland ecosystem at the Guassa Community Conservation Area, Ethiopia. Three encounters consisted of attempted predation on geladas by leopards, one of which was successful. All three attacks occurred in low-visibility microhabitats (dominated by tussock graminoids, mima mounds, or tall shrubs) that provided leopards with hidden viewsheds from which to ambush geladas. An additional four encounters did not result in an attempted attack but still document the consistently fearful responses of geladas to leopards. In encounters with leopards, geladas typically gave alarm calls (n = 7 of 7 encounters), reduced interindividual distances (n = 5), and collectively fled towards or remained at their sleeping cliffs (n = 7), the only significant refugia in the open-country habitat at Guassa. Geladas did not engage in mobbing behavior towards leopards. Encounters with leopards tended to occur on days when gelada herd sizes were small, raising the possibility that leopards, as ambush hunters, might stalk geladas on days when fewer eyes and ears make them less likely to be detected. We compare the behavioral responses of geladas to leopards at Guassa with those previously reported at Arsi and the Simien Mountains and discuss how gelada vulnerability and responses to leopards compare with those of other primate species living in habitats containing more refugia. Lastly, we briefly consider how living in multilevel societies may represent an adaptive response by geladas and other open-country primates to predation pressure from leopards and other large carnivores.     

Facilitating play through communication: significance of teeth exposure in the gorilla play face

Primate facial expressions (FEs) likely play an important role in primate society: through facial signals, individuals can potentially send and receive information and may benefit from coordinating their behavior accordingly. Many primates use a relaxed open mouth (ROM) facial display or “play face” (PF) during play behavior, where the mouth is open but teeth are covered. In addition to this conventional PF, however, Western Lowland gorillas (Gorilla gorilla gorilla) also use a full PF where the upper teeth are exposed. As the teeth are similarly exposed in the bared-teeth expression (which is a signal of appeasement, submission and/or affiliation), the full PF may be a blend of the PF and bared-teeth face, and have a different signal function to the PF alone. Focal animal sampling of captive Western Lowland gorillas (N=10) showed that the full PF was more often observed in intense rather than gentle play, and intense play bouts that featured the full PF were longer than those that featured only the PF. Both expressions were associated with an increase in affinitive behavior between sender and receiver postplay, but only the full PF was associated with an increase higher than that of play alone. Overall, the findings suggest that the full PF has an additional role in coordinating and maintaining play, possibly though reducing uncertainty in the receiver and confirming that play is only play.