Affiliation among Females in Wild Hamadryas Baboons (Papio hamadryas hamadryas)

Previous studies of hamadryas baboons have described a “star-shaped” sociogram, whereby the strongest social bonds within hamadryas one-male units are those between a leader male and his females and bonds among females are weak by comparison. This type of social organization has also been called “cross bonding” to distinguish it from the “female bonding” found in most papionin monkeys. Models of female primate socioecology have suggested that hamadryas baboons lack female bonding due to their reliance on scarce, widely-dispersed food resources. Here I report observational data from a wild population of hamadryas baboons in Ethiopia indicating that, while females varied widely in their frequency of social interaction with other females, most females spent about as much social time with other females as they did with their leader male and some females even crossed unit boundaries to interact with one another. The size of a unit was positively correlated with the tendency of its females to interact with other females and negatively correlated with the tendency of its females to interact with their leader male. Females were equally likely to spend social time with other females whether or not their leader male was available for social interaction at the time. Overall, this study suggests that a star-shaped sociogram does not necessarily characterize all hamadryas baboons and that female hamadryas may be, to some extent, female-bonded as well as cross-bonded. The lack of more pronounced female bonding in hamadryas is probably due to the behavior of males rather than to ecological factors

Patterns of reconciliation among captive gelada baboons (Theropithecus gelada)

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 is reconciliation. 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 rain 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

Ranging Behavior, Group Size, and Behavioral Flexibility in Ethiopian Hamadryas Baboons (Papio hamadryas hamadryas).

This study reports group size, home range size, daily path lengths, seasonal effects on ranging behavior and qualitative information on diet for a population of hamadryas baboons inhabiting the lowlands of the northern Rift Valley in central Ethiopia. The minimum home range size and daily path length for this population are similar to those reported for other populations of hamadryas baboons in Ethiopia and Saudi Arabia. Group sizes, however, are much larger than those in most other hamadryas populations for which published data are available. The large group sizes in this area may be related to the abundance of one food resource in particular, doum palm nuts. Overall, this study suggests that hamadryas baboons may be more flexible in some aspects of their behavioral ecology (e.g. group size) than in others (e.g. ranging behavior)

Two Takeovers in Wild Hamadryas Baboons

Hamadryas baboons exhibit a multi-level social structure in which several one-male units, each consisting of a ‘leader’ male and one or more females, comprise a band’ and two or more bands comprise a troop. Cohesion of each one-male unit is maintained by aggressive herding by its leader male [1]. Here I describe the consequences of 2 takeovers in a band of wild hamadryas baboons. I report evidence of infant mortality following takeovers, changes in female reproductive condition within 2 weeks after takeovers, and the reacquisition of a female by a deposed leader male, none of which has been previously reported for wild hamadryas baboons

Infant Mortality after Takeovers in Wild Ethiopian Hamadryas Baboons

In this paper, we report the first observational evidence of infanticide in wild hamadryas baboons. The study group inhabits the lowlands of the northern Rift Valley in Ethiopia and has been under observation for over 1200 hours, on and off, since October 1996. Here we report observations from August and September 2002 of the consequences of two takeovers of known females with black infants. After the first takeover, the respective infant disappeared and was presumed dead within eleven days of the takeover. After the second takeover, the infant incurred repeated severe aggression from its mother’s new leader male and eventually died four days after the takeover. We interpret these findings as support for the sexual selection hypothesis for the occurrence of male infanticide. We suggest that hamadryas leader males usually protect infants born into their units but may withhold this protection – or even directly attack and kill infants – after takeovers

The Fourth Level of Social Structure in a Multi-level Society: Ecological & 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]. Abegglen [1984] observed a 4th 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 2 observation periods this band comprised 2 large clans ranging in size from 7 to 13 OMUs. All band fissions occurred along clan lines, and most takeovers involved 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

30 Days in the life: daily nutrient balancing in a wild chacma baboon

For most animals, the ability to regulate intake of specific nutrients is vital to fitness. Recent studies have demonstrated nutrient regulation in nonhuman primates over periods of one observation day, though studies of humans indicate that such regulation extends to longer time frames. Little is known about longer-term regulation in nonhuman primates, however, due to the challenges of multiple-day focal follows. Here we present the first detailed study of nutrient intake across multiple days in a wild nonhuman primate. We conducted 30 consecutive all day follows on one female chacma baboon ( Papio hamadryas ursinus ) in the Cape Peninsula of South Africa. We documented dietary composition, compared the nutritional contribution of natural and human-derived foods to the diet, and quantified nutrient intake using the geometric framework of nutrition. Our focus on a single subject over consecutive days allowed us to examine daily dietary regulation within an individual over time. While the amounts varied daily, our subject maintained a strikingly consistent balance of protein to non-protein (fat and carbohydrate) energy across the month. Human-derived foods, while contributing a minority of the diet, were higher in fat and lower in fiber than naturally-derived foods. Our results demonstrate nutrient regulation on a daily basis in our subject, and demonstrate that she was able to maintain a diet with a constant proportional protein content despite wide variation in the composition of component foods. From a methodological perspective, the results of this study suggest that nutrient intake is best estimated over at least an entire day, with longer-term regulatory patterns (e.g., during development and reproduction) possibly requiring even longer sampling. From a management and conservation perspective, it is notable that nearly half the subject's daily energy intake derived from exotic foods, including those currently being eradicated from the study area for replacement by indigenous vegetation

Use of Palm Trees as a Sleeping Site by Hamadryas Baboons in Ethiopia

Hamadryas baboons sleep on cliffs throughout their range, and this can be attributed to the safety cliffs provide against predators in the absence of tall trees. In this paper, we report the first documented occurrence of hamadryas baboons sleeping in doum palm trees rather than on cliffs. Data derive from a study of hamadryas baboons at the Filoha site in lowland Ethiopia. During all-day follows, data were collected on travel patterns, band activity, and location. Variation in the baboons’ home range was characterized using vegetation transects. We discovered that one band in this population, Band 3, occasionally slept in doum palm trees (Hyphaene thebaica). The palm tree sleeping site differed from other palm fragments in the baboons’ home range in that it contained a higher density of palm trees. Possible factors influencing this unique use of palm trees as a sleeping site include access to palm fruit, avoiding contact with Afar nomads, avoiding sharing sleeping cliffs with other bands, protection from predators, and the lack of cliffs in a section of the baboons’ home range. Evidence from this study suggests that the palm tree sleeping site is used because it affords better protection from predators than other palm fragments in an area of the band’s home range that does not contain cliffs