Humans as primates: The social relationships of Efe pygmy men in comparative perspective

The Efe are short-statured specialized hunger-gatherers living in the moist tropical forest in northeast Zaire. They live in small mobile groups averaging 18 individuals and practice viripatrilocal residence — what primatologists refer to as male philopatry and female dispersal. This study uses methods commonly employed by primatologists to study the social relationships of Efe men. It compares their association and affiliation patterns with those of two nonhuman primate species that show male philopatry and female transfer. The analyses of 376 hr of focal behavior observations on 16 Efe men reveal that the majority of their associations were with other adult men. Men associated preferentially with kin over non-kin, and with close kin more than with distant kin. Men's close relationships, or companionships,sensu Smuts' (1985) friendships among anubis baboons, were predominantly with other adult men; however, each man who cohabited with a woman had his strongestcompanionship by far with that woman. These quantitative measures of affinity are consistent with the Efe's pattern of viripatrilocal residence, where-by males remain in their natal group with their close male kin and females join or are recruited from other patriclans. The social relationships of Efe men are similar in some respects to those of hamadryas and chimpanzees; however, Efe men's social networks are larger and more fluid. We speculate that the explanation proposed for male philopatry and female dispersal among nonhuman primates also applies to the Efe.     

Demographic influences on the hunting behavior of chimpanzees

We investigated hunting in an unusually large community of wild chimpanzees at Ngogo in the Kibale National Park, Uganda. Aspects of predation were recorded with respect to the prey, the predators, and hunting episodes. During 23 months of observation, the Ngogo chimpanzees caught 128 prey items from four primate and three ungulate species. Chimpanzees preyed selectively on immature red colobus primarily during group hunts, with adult males making the majority of kills. Party size and composition were significant predictors of the probability that chimpanzees would hunt and of their success during attempts. Chimpanzees were more likely to hunt red colobus if party size and the number of male hunters were large; party size and the number of male hunters were also significantly larger in successful compared with unsuccessful hunts. The Ngogo chimpanzees did not appear to hunt cooperatively, but reciprocal meat-sharing typically took place after kills. Hunts occurred throughout the year, though there was some seasonality as displayed by periodic hunting binges. The extremely high success rate and large number of kills made per successful hunt are the two most striking aspects of predation by the Ngogo chimpanzees. We compare currently available observations of chimpanzee hunting behavior across study sites and conclude that the large size of the Ngogo community contributes to their extraordinary hunting success. Demographic differences between groups are likely to contribute to other patterns of interpopulation variation in chimpanzee predation. Am J Phys Anthropol 109:439–454, 1999. © 1999 Wiley-Liss, Inc.     

Blood,solidarity, status,and honor: The sexual balance of power and spousal abuse in Sonora,Mexico

Independent samples of 128 women and 106 men were interviewed in a study site in Hermosillo, Sonora, Mexico. Respondents were screened for involvement in a committed sexual relationship during the past year, but not with each other. Questions pertained to family structure, support, and conflict; females reported on victimization by spousal aggression and males on perpetration. Previously documented effects of their partner's mate quality (“sex”) and socioeconomic status (“money”) were cross-culturally replicated. The following family structure parameters were also measured: (1) the local density of female kin, (2) the local density of male kin, (3) the social support provided by local kin, (4) the socioeconomic status of close kin, and (5) the “culture of honor” revenge ideology of the respondents. The same interactions of local density of male kin that protected women from spousal abuse also empowered men to perpetrate it. The risk of spousal abuse was mitigated by the “sexual balance of power” between the family structures of potential victims and potential perpetrators. Evidence was also found partially supporting several alternative hypotheses tested regarding local cultural and ideological mechanisms (culture of honor and patriarchal beliefs), major dimensions of psychopathology (anxiety and depression) and substance abuse (alcohol), and indicators of general criminality (permissive and risk-taking attitudes).     

Co–Residence between Males and Their Mothers and Grandmothers Is More Frequent in Bonobos Than Chimpanzees

In long–lived social mammals such as primates, individuals can benefit from social bonds with close kin, including their mothers. In the patrilocal chimpanzee (Pan troglodytes spp.) and bonobo (Pan paniscus), sexually mature males reside and reproduce in their natal groups and can retain post-dependency bonds with their mothers, while immatures of both sexes might also have their paternal grandmothers available. However, quantitative information on the proportion of males and immatures that co-reside with both types of these close female relatives is limited for both species. Combining genetic parentage determination and group composition data from five communities of wild chimpanzees and three communities of wild bonobos, we estimated the frequency of co-residence between (1) mature males and their mothers, and (2) immature males and females and their paternal grandmothers. We found that adult males resided twice as frequently with their mothers in bonobos than in chimpanzees, and that immature bonobos were three times more likely to possess a living paternal grandmother than were immature chimpanzees. Patterns of female and male survivorship from studbook records of captive individuals of both species suggest that mature bonobo females survive longer than their chimpanzee counterparts, possibly contributing to the differences observed in mother–son and grandmother–immature co-residency levels. Taking into account reports of bonobo mothers supporting their sons'' mating efforts and females sharing food with immatures other than their own offspring, our findings suggest that life history traits may facilitate maternal and grandmaternal support more in bonobos than in chimpanzees.     

Hypothetical rankings of prospective husbands for female kin in lowland Nicaragua: consensus analysis indicates high agreement and associations with wealth and hunting skill

In preindustrial societies, kin may exert influence on the mating choices of women, but there have been few systematic studies of the preferred characteristics of husbands for female kin. In an indigenous Mayangna and Miskito community, photographs of 29 male household heads were presented to informants, who ranked the men on three characteristics: desirability as a spouse, hunting ability and wealth. For the desirability rankings, informants were asked to consider the advice that they would give to young female relatives and rank the men based on the qualities that such women should seek in a husband. Consensus analysis indicates that there is high agreement among informants on all three sets of rankings. There is no evidence that the age and sex of informants are associated with variation in evaluations of the desirability of men, which suggests that the evaluations by reproductively active women do not significantly differ from rankings by other informants. Multivariate analysis indicates that perceptions of both a man's wealth and his hunting ability are positively associated with his desirability as a prospective husband for female kin. By contrast, a strong kin-based social network, as measured by the presence of consanguineal kin in the community, seems unimportant to a man's desirability as a husband. Although it remains unclear to what extent hunting ability is a signal of phenotypic quality, these results support predictions that individuals will encourage female kin to marry men who are good resource providers. Finally, compared to a conventional reliability analysis, consensus analysis is demonstrated as a superior method for assessing both unidimensionality and subgroup variation in informant rankings.     

Genetic relatedness in groups of the humbug damselfish Dascyllus aruanus: small, similar-sized individuals may be close kin

Kin selection plays an important role in the evolution of social behaviour in terrestrial systems. The extent to which kin selection influences the evolution of social behaviour in marine systems is largely unexplored. Generally, it is considered that kin selection is irrelevant in marine systems, because it is assumed that the dispersing larval phase of marine organisms will break up kin associations. Here, we challenge this assumption and investigate the opportunity for kin selection in a coral reef fish: the humbug damselfish Dascyllus aruanus . This fish lives in groups composed of a large male and a number of smaller females and nonbreeders. We use 10 polymorphic microsatellite loci to assess the relatedness of 265 individuals from 35 groups. The mean coefficient of relatedness among group members is 0.01 ± 0.04, suggesting that individuals are not associated with close relatives. However, the distribution of pairwise relatedness of individuals within groups has an overabundance of positive values, and indicates that there might be 35 pairs of close relatives within groups. Further analyses reveal that close relatives likely are similar in size and small in size, suggesting that they might have recruited together. We conclude that it is possible for kin selection to operate in D. aruanus , but kin recognition will be a prerequisite for such selection. This study reveals that individuals can be associated with close relatives, and there is a hidden potential for kin selection, during certain parts of the life cycle of coral reef fishes.     

Bonds of bros and brothers: Kinship and social bonding in postdispersal male macaques

Group‐living animals often maintain a few very close affiliative relationships—social bonds—that can buffer them against many of the inevitable costs of gregariousness. Kinship plays a central role in the development of such social bonds. The bulk of research on kin biases in sociality has focused on philopatric females, who typically live in deeply kin‐structured systems, with matrilineal dominance rank inheritance and life‐long familiarity between kin. Closely related males, in contrast, are usually not close in rank or familiar, which offers the opportunity to test the importance of kinship per se in the formation of social bonds. So far, however, kin biases in male social bonding have only been tested in philopatric males, where familiarity remains a confounding factor. Here, we studied bonds between male Assamese macaques, a species in which males disperse from their natal groups and in which male bonds are known to affect fitness. Combining extensive behavioural data on 43 adult males over a 10‐year period with DNA microsatellite relatedness analyses, we find that postdispersal males form stronger relationships with the few close kin available in the group than with the average nonkin. However, males form the majority of their bonds with nonkin and may choose nonkin over available close kin to bond with. Our results show that kinship facilitates bond formation, but is not a prerequisite for it, which suggests that strong bonds are not restricted to kin in male mammals and that animals cooperate for both direct and indirect fitness benefits.     

On the importance of kin relations to canadian women and men

Sex differences in the salience and meaning of kin relations for contemporary Canadians were examined in two studies. In study 1, 24 opposite-sex adult sibling pairs were asked to reconstruct their kindreds as fully as possible, following a computerized menu. Sisters almost invariably recalled more relatives than did their brothers, especially living and matrilateral relatives. In study 2, a questionnaire administered to 150 female and 150 male undergraduates explored the relevance of kinship to characterizations of the self (“Who are you?”) and to nominations of one's closest social relationships. Women were much more likely than men to refer to their kinship statuses in characterizing themselves (I am a daughter, a sister, etc.), whereas 28% of men and only 8% of women mentioned their surnames (I am a Smith, Jones, etc.). Women and men were about equally likely to name a relative, as opposed to a mate or friend, as the person to whom they feel closest, but women more often nominated a parent (especially mother) and men a sibling (especially an older sister). These sex differences are discussed in relation to possible differences in how women and men make use of family ties.     

Cortisol response of wild ungulates to trauma situations: hunting is not necessarily the worst stressor

Animal welfare concerns are becoming a central issue in wildlife management and conservation. Thus, we investigated stress response of wild ungulates to potentially traumatic situations (shooting injuries, vehicle collisions, entanglement, injuries or diseases) and hunting methods (stalking, battues and hunts with dogs) by means of serum cortisol concentrations from blood collected from killed animals. Cortisol levels in roe deer ranged below and in wild boar above levels for moose, red deer and fallow deer (hence, pooled as a group “deer”). Apart from species, cortisol concentration in trauma situations was mainly explained by trauma type and presence of disturbance after the trauma event. Effect of trauma type differed significantly for “deer”, with animals caught in fences and suffering vehicle collisions experiencing higher cortisol levels than animals injured by shooting. Differences between hunting methods were observed in the cervids (“deer” and roe deer), with stalking leading to lower cortisol levels than hunts with dogs (both groups) and battues (roe deer). Events both before and after the shot, such as duration of pursuit prior to shooting, location of injury, trauma length and presence of disturbance after the shot were relevant for cortisol levels in hunted cervids. Our results indicate that search teams tracking and euthanising wounded animals should behave in a calm way to minimise disturbance. Still, it is important to acknowledge that many situations described in the literature, i.e. reindeer handling, roe deer captures and red deer yarding, seem even more stressful, beside vehicle collisions, than most hunting methods.     

Male–male relationships in chimpanzees and the evolution of human pair bonds

The evolution of monogamy has been a central question in biological anthropology. An important avenue of research has been comparisons across “socially monogamous” mammals, but such comparisons are inappropriate for understanding human behavior because humans are not “pair living” and are only sometimes “monogamous.” It is the “pair bond” between reproductive partners that is characteristic of humans and has been considered unique to our lineage. I argue that pair bonds have been overlooked in one of our closest living relatives, chimpanzees. These pair bonds are not between mates but between male “friends” who exhibit enduring and emotional social bonds. The presence of such bonds in male–male chimpanzees raises the possibility that pair bonds emerged earlier in our evolutionary history. I suggest pair bonds first arose as “friendships” and only later, in the human lineage, were present between mates. The mechanisms for these bonds were co-opted for male-female bonds in humans.     

Population Genetics,Dispersal, and Kinship Among Wild Squirrel Monkeys (Saimiri sciureus macrodon): Preferential Association Between Closely Related Females and Its Implications for Insect Prey Capture Success

Little genetic information is available to evaluate hypotheses concerning the parameters that affect population genetic structure in primate taxa that exhibit interspecific variation in social systems, such as squirrel monkeys (Saimiri). Here, we used genetic data to assess dispersal patterns, kin structure, and preferential association with same-sex kin in a wild population of Saimiri sciureus macrodon. We also analyzed behavioral data to assess whether individuals that maintain shorter interindividual distances show increased insect foraging success. If there was greater male than female dispersal, then we expected mean pairwise relatedness, F _ST values, and intragroup mean corrected assignment indices to be greater among adult females than among adult males. We also expected matrices of pairwise affinity indices (PAIs) for “association” (time spent ≤5 m) and “proximity” (time spent ≤10 m) among female dyads to positively correlate with a matrix of female pairwise relatedness. Not only did we find support for female philopatry, but we also found significant positive relationships between the relatedness matrix and each of the PAI matrices: females were more likely to be associated with (and proximal to) close female relatives than more distant relatives or unrelated individuals. Foraging analyses revealed that females had higher insect capture rates than males, and this sex difference may be related to a smaller mean interindividual distance among closely related female group members. Our result shows how estimates of genetic relatedness are useful for testing predictions regarding the evolution of sex-biased dispersal patterns, as well as potential relationships between kin-biased social behaviors and foraging success.     

Fine‐scale genetic structure and helping decisions in a cooperatively breeding bird

In animal societies, characteristic demographic and dispersal patterns may lead to genetic structuring of populations, generating the potential for kin selection to operate. However, even in genetically structured populations, social interactions may still require kin discrimination for cooperative behaviour to be directed towards relatives. Here, we use molecular genetics and long‐term field data to investigate genetic structure in an adult population of long‐tailed tits Aegithalos caudatus, a cooperative breeder in which helping occurs within extended kin networks, and relate this to patterns of helping with respect to kinship. Spatial autocorrelation analyses reveal fine‐scale genetic structure within our population, such that related adults of either sex are spatially clustered following natal dispersal, with relatedness among nearby males higher than that among nearby females, as predicted by observations of male‐biased philopatry. This kin structure creates opportunities for failed breeders to gain indirect fitness benefits via redirected helping, but crucially, most close neighbours of failed breeders are unrelated and help is directed towards relatives more often than expected by indiscriminate helping. These findings are consistent with the effective kin discrimination mechanism known to exist in long‐tailed tits and support models identifying kin selection as the driver of cooperation.     

Inbreeding avoidance in rhesus macaques: Whose choice?

Whether nonhuman primates avoid copulating with close kin living in their social group is controversial. If sexual aversion to relatives occurs, it should be stronger in females than in males because of females' greater investment in each offspring and hence greater costs resulting from less viable offspring. Data presented here show that adult male rhesus macaques breeding in their natal groups at Cayo Santiago experienced high copulatory success, but copulated less with females of their own matrilineages than with females of other matrilineages. Adult females were never observed to copulate with males of their own matrilineage during their fertile periods. Although natal males sometimes courted their relatives, examination of two measures of female mate choice showed that females chose unrelated natal males over male kin. Female aversion to male kin was specific to the sexual context; during the birth season, females did not discriminate against their male relatives in distributing grooming. Evolved inbreeding avoidance mechanisms probably produce different outcomes at Cayo Santiago than in wild rhesus macaque populations. Gender differences in sexual aversion to relatives may be partly responsible for differences between studies in reported frequency of copulations by related pairs. © 1993 Wiley-Liss, Inc.     

Enclosure utilization,activity budgets,and social behavior of captive chamois (Rupicapra rupicapra) during the rut

An observational study of chamois behavior during the rut was conducted at the Los Angeles Zoo. The herd consisted of an adult male, two adult females, two subadult females, and two kids (1.1). During the 13-week study, observers collected scan data on all animals and recorded all occurrences of selected social behaviors during interactions which involved the adult male. Scan observations showed that open areas of the enclosure close to the public were the least preferred, and areas with good rest places were used most. Overall the herd spent 73% of their time stationary, 13% foraging/feeding, 6% moving, and less than 5% each in object investigation, maintenance, play, and social behavior. The adult male rested and fed less, and stood vigilant and engaged in social behavior more frequently than the others. Nearest neighbor data showed clear patterns of kin association beyond the mother-last kid bond. The adult male interacted most often with the regular keepers, the subordinate female and the oldest subadult female. Interactions with the females consisted mostly of herding and sexual behaviors, while those with keepers were almost exclusively competitive/aggressive. While most findings paralleled those from studies of wild chamois, no study has previously reported long-lasting associations among kin.     

Kin Associations during Nest Founding in an Allodapine Bee Exoneura robusta: do Females Distinguish between Relatives and Familiar Nestmates?

True recognition of kin can have important fitness consequences in terms of directing altruistic behaviours toward close relatives (nepotism) and avoiding inbreeding. However, recent evidence suggests that some social insect species cannot or do not distinguish their closest relatives from among nestmates in important fitness-based contexts. Such findings are relevant to kin selection theories where individuals are expected to preferentially rear close relatives in order to gain inclusive fitness benefits. Here, allozyme markers are used to examine whether female Exoneura robusta individuals preferentially nest with their closest kin when given a choice of familiar previous nestmates. The results suggest these bees do not prefer kin over non-kin nestmates. Kin associations during nest founding in this species are probably due to philopatry and/or association with previously familiar nestmates.     

“KIN RECOGNITION” AMONG SPADEFOOT TOAD TADPOLES: A SIDE-EFFECT OF HABITAT SELECTION?

Many animals modify their behavior toward unfamiliar conspecifics as a function of their genetic relatedness. A fundamental problem of any kin recognition study is determining what is being recognized and why. For anuran tadpoles, the predominant view is that associating with relatives is kin-selected because these relatives may thereby accrue benefits through increased growth or predation avoidance. An alternative view is that kin associations are simply a side-effect of habitat selection and thus do not represent attempts to identify kin per se. In the laboratory, spadefoot toad tadpoles (Scaphiopus multiplicatus) preferentially associated with unfamiliar siblings over unfamiliar nonsiblings, as do other anurans. However, same age tadpoles also were more likely to orient toward unfamiliar nonsiblings reared on the same food (familiar food) than toward unfamiliar siblings that were reared on unfamiliar food. These results, together with the results of previous tadpole kin recognition studies, suggest that tadpoles orient toward cues learned early in ontogeny, regardless of the cues' source. Tadpoles that preferentially associated with cues learned from their environment at birth would tend to be philopatric. Censuses of 14 natural ponds revealed that tadpole density remained greatest near oviposition sites until four days before metamorphosis. Tadpole philopatry may be advantageous: tadpoles restricted to their natal site had greater growth and survivorship than did their siblings restricted to randomly selected sites elsewhere within the same pond. Thus kin affiliative tendency observed in the laboratory in this and perhaps other species of anurans may be a byproduct of habitat selection. Since kin discrimination in animals is most commonly assayed as orientation toward kin, it follows that many examples of “kin recognition” may not represent true attempts to identify kin as such, but rather may reflect some other recognition system that is under entirely different selective pressures.     

Changes in nearest‐neighbor associations in a captive group of western lowland gorillas after the introduction of five hand‐reared infants

The successful management of a captive gorilla population often necessitates the hand‐rearing of infants and their subsequent re‐integration into social groups of conspecifics. In the present study we quantified the changes in nearest‐neighbor associations in a group consisting of a silverback male, three adult females, and two sub‐adult females after the introduction of five hand‐reared infants. Additionally, we examined the associations among kin and non‐kin group members to determine whether genetic relatedness was a factor influencing the integration of the infants into the group and the subsequent patterns of association among infants and adults. Results showed that after the introduction, the silverback male spent >60% of his time in close proximity to an infant and 10% of his time within a “cluster” of infants. There was a significant change in a female's nearest‐neighbor associations; however, the change did not include an infant. The most significant finding among infants was a strong bias by each to associate with another infant. When the infants associated with an adult, three of the five associated most with the silverback male (P < 0.001), whereas the other two infants distributed their time among all the adults. The most significant change in behavior patterns was exhibited by one of the sub‐adult females who displayed parental behaviors 18% of the time compared to <1% for all other females. Adults and one sub‐adult female associated significantly more often with related infants compared to unrelated infants (P < 0.025), and the infants showed a bias to associate with another related infant (P < 0.0001). Results of an infant's association with an adult showed that three of the five infants preferred to associate with a related adult (P < 0.0001). An individual's age, sex, and behavioral profile may have also influenced association patterns among group members. These findings lend strong support to the importance of peer groups and the presence of a silverback male for facilitating the integration of hand‐reared infants into established adult groups. Zoo Biol 18:261–278, 1999. © 1999 Wiley‐Liss, Inc.     

Distastefulness as a defense mechanism in Aplysia brasiliana (Mollusca: Gastropoda)

An unusual courtship pattern for fiddler crabs is described from field observations in Panama. This behavior pattern, referred to here as “directing,” differs considerably from the more frequently observed communal courtship system found in close relatives of Uca deichmanni. A male involved in “directing” approaches a female and attempts to carry or maneuver her into his burrow for mating. The female usually struggles to escape from the male. This activity often attracts other males which attempt to “direct” the female if she escapes from the first male. A male is most successful in “directing” a female into his burrow if a) he is larger than the female, b) the female is wandering (a sign of physiological receptivity) prior to the “directing” attempt, and c) several males attempt to “direct” the female at once. The results suggest that females are choosing mates by inciting several males to compete for them. The males which successfully “direct” the struggling females are probably the most fit males.     

Premating Behavior in the Subgenus Limia (Pisces: Poeciliidae): Sexual Selection and the Evolution of Courtship

A three-year field-study of Richardson's ground squirrels was conducted to assess whether alarm calling functions to warn close relatives (“kin selection” hypothesis) or manipulate conspecifics (a “selfish” hypothesis). S. richardsonii had distinct calls for terrestrial and aerial predators, and the responses of squirrels varied appropriately according to the context of calls, implying that calling conveyed correct information concerning the nature of the danger. Alarm calling elicited by naturally occurring encounters with potential predators during 454 h of observation, and by a thrown frisbee in 70 experimental trials, was not equally probable for all age/sex classes. Squirrels were most likely to call when they had offspring or siblings nearby, which is supportive of the hypothesis that alarm calling is maintained by kin selection. Adult males, residing in the vicinity of either their probable progeny or their nonlittermate half-siblings, were the most likely age/sex class to call during the lactation period when young were below ground and were most vulnerable. I conclude that alarm calling by Richardson's ground squirrels is nepotistic rather than manipulative.     

Interspecific communicative and coordinated hunting between groupers and giant moray eels in the Red Sea

Intraspecific group hunting has received considerable attention because of the close links between cooperative behaviour and its cognitive demands. Accordingly, comparisons between species have focused on behaviours that can potentially distinguish between the different levels of cognitive complexity involved, such as “intentional” communication between partners in order to initiate a joint hunt, the adoption of different roles during a joint hunt (whether consistently or alternately), and the level of food sharing following a successful hunt. Here we report field observations from the Red Sea on the highly coordinated and communicative interspecific hunting between the grouper, Plectropomus pessuliferus, and the giant moray eel, Gymnothorax javanicus. We provide evidence of the following: (1) associations are nonrandom, (2) groupers signal to moray eels in order to initiate joint searching and recruit moray eels to prey hiding places, (3) signalling is dependent on grouper hunger level, and (4) both partners benefit from the association. The benefits of joint hunting appear to be due to complementary hunting skills, reflecting the evolved strategies of each species, rather than individual role specialisation during joint hunts. In addition, the partner species that catches a prey item swallows it whole immediately, making aggressive monopolisation of a carcass impossible. We propose that the potential for monopolisation of carcasses by one partner species represents the main constraint on the evolution of interspecific cooperative hunting for most potentially suitable predator combinations.