Carolyn L. Ehardt

The influence of kinship and socialization on aggressive behaviour in rhesus monkeys (Macaca mulatta)

Abstract Among the 100 rhesus monkeys living in a social group studied over a period of 17 months, group members showed disproportionately more aggression to kin than non-kin. Mothers were particularly likely to show aggression towards offspring. The more extreme forms of response involving contact aggression were most often directed towards kin, particularly younger kin. Aggression received from kin declined as animals matured; the decline was more rapid for males than females. By adolescence, males no longer received disproportionately more aggression from kin and, as adults, natal males received significantly less aggression from kin. The forms of agonistic expression directed toward kin did not include mobbing a defeated victim or joining the aggression of another group member against kin. Females of all ages directed their agonistic behaviour disproportionately more often toward kin, whereas the relative frequency of male agonistic involvement with kin deceased with age. These data support the hypothesis that aggression is used as one of the mechanisms in socialization and that matrilines are particularly active in the socialization of immature rhesus monkeys.

Age-sex differences in the expression of agonistic behavior in rhesus monkey (Macaca mulatta) groups

Both age and sex influence rhesus monkey agonistic behavior. In intragroup episodes, submission was most frequent in juveniles, but aggression increased steadily with age, albeit much more sharply in females. As infants, males were more often involved in agonistic behavior than were females, but this sex difference reversed with age. A notable change in the frequency and forms of agonistic expression occurred in adolescent males. By the time they became adults, their participation in agonistic episodes was silent and brief and rarely involved biting. Adolescent males received high frequencies of aggressive responses, and this is hypothesized to account for the marked shift in adult male patterns of participation in intragroup agonistic interactions, as relative to females whose basic pattern of agonistic expression does not change with age.

Demographic variation among Udzungwa red colobus in relation to gross ecological and sociological parameters

We evaluated variation in group size and composition of Udzungwa red colobus (Procolobus gordonorum) in relation to gross-habitat and sociological parameters. The endangered species is endemic to the Udzungwa Mountains and nearby forests in the Kilombero Valley of south-central Tanzania. We counted 63 groups in 10 forests, ranging in altitude from 250 to 1,800 m. Group size ranged from 7 to 83 (x = 36.3) individuals and adult sex ratios (females/male) ranged from 1.5 to 7.3 (x = 3.5), excluding solitary individuals. Group size was influenced by several habitat parameters, including tree density, degree of deciduousness, and forest size. Groups were largest in large blocks of mature, moist, mixed evergreen and semideciduous forests, but group size is not correlated with altitude. Groups in a highly degraded forest appeared to have fission-fusion societies. The effect of habitat quality on age-sex composition of groups was most apparent in natality and less so in survivorship of adult females and juveniles. The number of adult males in groups accounted for 50% of the variance in group size and 34–39% of the variance in numbers of adult females in groups. Habitat quality affects natality more than demographic parameters do. Groups with a low proportion of adult females had greater juvenile survivorship, perhaps because of lower food competition between these two classes. We proffer hypotheses based on our study and previous intertaxonal comparisons to explain cause and effect relationships between habitat quality and demography. Finally, our study demonstrates the importance of large blocks of old-growth forest to the conservation of Udzungwa red colobus, and we make recommendations for conservation and research.

Matrilineal overthrows in rhesus monkey groups

Between January 1976 and February 1983, there were four overthrows of the highest-ranking matriline in a group of rhesus monkeys. The overthrows were the result of members of multiple mainlines jointly attacking the adult female and adolescent members of the ranking matrilines. In three cases, the next-ranking matriline assumed highest position, while the surviving members of the deposed matrilines fell to the bottom of the hierarchy. Dominance relationships among other group members remained stable. High-ranking adult males vigorously defended the victims, but their efforts were ineffective. Unlike other members of the matrilines, adolescent males were not cohesive with their relatives during the overthrows and did not defend them. These young males were attacked by some adult and adolescent males. These incidents demonstrate the aggressive potential of females and underscore the importance of baboon and macaque females as the enduring and stable core of their social organization. The lack of effective participation by adult males demonstrates the independent functioning of this female core. These overthrows were similar in structure to incidents reported for other captive rhesus colonies and feral baboons, but no explanatory hypothesis posed accounts for all the data. Overthrows may be examples of opportunistic female behavior producing rapid changes in the normally stable female dominance system. Even if such events are rare, the deaths and reproductive failures within deposed matrilines may drastically affect inclusive fitness, counteracting the reproductive advantages of several years of dominance for a matriline.

Protective status, ecology and strategies for improving conservation of Cercocebus sanjei in the Udzungwa Mountains, Tanzania

Sanje mangabeys (Cercocebus sanjei), first described in 1981, are among the most endangered primates in the world. They are endemic to the Udzungwa Mountains of Tanzania, in a biogeographic region designated one of the world’s biodiversity hotspots. Conservation research since 1997 has documented the presence of the mangabey in only 3 of the relict montane forest blocks of the Udzungwas. The total population, possibly < 1,500 animals, is fragmented and not adequately protected. A substantial proportion (perhaps 40%) live in forest reserves outside the protective confines of the Udzungwa Mountains National Park, and they are affected by habitat loss and hunting. Efforts to improve their conservation status include assessment of distribution, relative abundance, and habitat quality, and initiation of observational research with habituated individuals to acquire critically important data on their habitat requirements, diet, movement patterns, socioecology, and community ecology. These interrelated research activities should contribute to effective management for conservation, provide baseline information to support current efforts to expand the boundaries of the national park, and guide potential future establishment of corridors between the major forests known to support mangabey groups.

Selective interference in rhesus monkey (Macaca mulatta) intragroup agonistic episodes by age−sex class

Adult male interference in agonistic episodes is strongly biased against adolescent and adult male participants, whereas adult female interference is biased in favor of kin and in support of younger animals against older animals. Although natal males also are biased in favor of their kin, their selective targeting of sexually mature males is independent of kinship. Adolescent males target adult males, but only in defense of kin. This selective interference against adolescent and adult males by adult males has the potential to profoundly modify male agonistic participation in intragroup encounters after puberty. Because female support is influenced primarily by kinship, females less consistently interfere against male agonistic participants. Adult males may therefore play an important role in the socialization of male agonistic expression.

The Recently Described Highland Mangabey, Lophocebus kipunji (Cercopithecoidea, Cercopithecinae): Current Knowledge and Conservation Assessment

Abstract The highland mangabey (Lophocebus kipunji), described and named in 2005, is the first monkey to be discovered in Africa since 1984. This species, endemic to Tanzania, was independently discovered by two research groups, one working in Ndundulu Forest in the Udzungwa Mountains, the other ∼350 km to the southwest in the Rungwe-Livingstone Forest in the Southern Highlands. Lophocebus kipunji is an arboreal omnivore with a morphology and vocal repertoire distinct from other mangabeys (Lophocebus spp. and Cercocebus spp.). Although few data are available, studies of its molecular biology, ecology, behavior, and conservation status are underway. Lophocebus kipunji is Critically Endangered as a result of hunting and loss of habitat, which have produced small and fragmented populations. Efforts to improve the conservation status of both Ndundulu Forest and Rungwe-Livingstone Forest are ongoing, as well as augmentation of community-based conservation programs with expanded law enforcement. Research, long-term monitoring, effective law enforcement, and additional conservation projects are all essential to the long-term survival of L. kipunji.

Birth-season interactions of adult female Japanese Macaques(Macaca fuscata) without newborn infants

The affiliative interactions of 11 adult female Japanese macaques that did not deliver an infant during the 1981 birth season of the Arashiyama West troop were examined. Consideration was given to the effects of kinship as a structuring element in these birth-season interactions and to the degree of association with various categories of troop members based on age, sex, and (in the case of adult females) whether or not the females were new mothers. Females without infants interacted predominantly with their yearling off-spring, although it was the behavior of the offspring that precipitated the interaction. These females were active in soliciting affiliation with nonkin new mothers, whereas female matrilineal relatives with new infants approached and remained in proximity to them more than did nonrelated new mothers. Females without newborns groomed and approached nonkin infants more than infants within their own matriline, and these infants were predominantly those of females in the highest-ranking matriline of the troop. Adult males were responsible for 40% of all grooming received from nonkin by the females without newborns, and these males approached them significantly more than did other adult females without infants. These patterns demonstrate that the structure of social relationships is influenced by the particular dynamics of troop contexts such as birth seasons, as well as by enduring, broad-based affinities which are less affected by cyclic changes in troop context.