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.     

Intergroup Relationships in Western Black-and-White Colobus, <Emphasis Type="Italic">Colobus polykomos polykomos</Emphasis>

We investigated patterns of intergroup relationships in western black-and-white colobus, Colobus polykomos, in Taï National Park, Côte d'Ivoire, between 1993 and 1999. They live in one-male multifemale units, and demonstrate male dispersal and occasional dispersal by females. Solitary males and all-male bands are absent or very rare. Our aim was to investigate the function of female and male aggression during intergroup interactions. The species is particularly interesting because, in contrast to predictions from socioecological models, female aggression occurs during intergroup interactions in combination with female dispersal. Home ranges of neighboring groups overlapped considerably and groups lacked an area of exclusive access. Intergroup interactions occurred once every 6.6 observation days. Encounters were either peaceful (12%), or involved displays and threats (25%) or chases and fights (63%). Females interacted in 74% and males in 98% of aggressive intergroup encounters. We found little to no indication that male and female aggression correlated with the presence of food, importance of a location, or presence of infants or receptive females. However, females were more often aggressive during the months when the group depended strongly on seeds from Pentaclethra macrophylla. We also observed forays by males to other groups. Forays occurred on average once every 20 observation days. In 75% of the forays, the intruding male chased members of the target group. In 25% of the forays 1–3 females joined their male but females never attacked the target group. Our main study group was the target of such forays significantly more often when young infants were present in the group than when not. We conclude that female aggression between groups was related to food procurement and that male forays might be related to infanticide.     

Female sexual swellings in the Asian colobine Simias concolor

During a preliminary study of pig-tailed langurs (Simias concolor) in the Pagai Islands, Indonesia, it was discovered that females exhibited conspicuous swelling of the urogenital triangle. The pig-tailed langur is the first Asiatic colobine found to have prominent sexual swellings and the only colobine with sexual swellings that lives in one-male groups. Because all anthropoids with conspicuous sex skin typically live in groups having female-biased adult sex ratios, it is possible that females might compete amongst themselves for the male in one-male groups, or the best males in multimale groups. Sexual swellings may therefore have resulted from sexual selection for signals attractive to males in female-female competition, as suggested earlier by Bercovitch (California Anthropologist 8:9–12, 1978). Prolonged observation of recognizable individuals will be required to test this hypothesis in the pig-tailed langur and other species.     

Aggression with mixed age-sex groups of bolivian squirrel monkeys following single animal introductions and new group formations

The social organization of the Bolivian squirrel monkey (Saimiri boliviensis boliviensis) is thought to be sexually segregated, with males and females forming separate social groups during the nonbreeding season. To investigate the influence of this social order on patterns of aggression, controlled single animal introductions within established groups and establishment of new groups were studied in a systematic manner. Behavioral observations were made using an all-occurrences technique to sample all agonistic interactions. In study I, 4 animals of each age-sex class (adult males and females, juvenile males and females) were introduced one at a time into 4 different social groups composed of 1 adult male and 8 to 10 adult females. Behavioral observations were made prior to and after the introductions. Newly introduced adult males received significantly more contact aggression than other age classes. Only the adult females increased aggression after the introduction of new animals. In study II, new social groups were formed and behavioral observations were made following formation. One group was formed from 7 pairs of familiar females and an unfamiliar adult male. This group had a high frequency of aggression during the first half hour, with contact aggression rising to peaks at 3 and 5 h. The second group consisted of 10 familiar females, 2 pairs of familiar females and an unfamiliar male. There was a significant peak in contact aggression 3 h into the observation.     

Intergroup encounters in wild white-faced capuchins (Cebus capucinus)

Wrangham (1980) hypothesized that knowledge of the nature of intergroup encounters is crucial to understanding primate social relationships and social organization. I studied a single social group of wild white-faced capuchins over a period of 26 months and observed 44 encounters between social groups during 3703 hr of observation. All intergroup encounters consisted of predominantly hostile social interactions. However, nonaggressive interactions between males of different social groups occurred in a few cases. Adult males were the sole participants in 39 encounters and the primary participants in all 44 encounters. The alpha male was the most frequent participant. High-ranking females participated aggressively in five encounters, and low-ranking females never participated. There was no stable intergroup dominance hierarchy. I hypothesize that the need for male-male cooperation in intergroup aggression is an important factor influencing the quality of intragroup male-male relationships. Behavior during intergroup encounters is consistent with the idea that intergroup behavior is related to male reproductive strategies, but inconsistent with the idea that intergroup aggression is related to female defense of resources. The possibility that males are “hired guns” (Wrangham, 1980) cannot be ruled out.     

黄毛鼠婚配制度初探:熟悉性对两性间行为的影响

为探究黄毛鼠的婚配制度,通过雌雄黄毛鼠对熟悉和陌生异性鼠的选择实验和遭遇实验,分析了熟悉性对两性间行为的影响.结果发现,选择实验中雌鼠对陌生雄鼠的关注频次比对熟悉雄鼠的更多;遭遇实验中尽管雌鼠探究和自身修饰行为、雄鼠的活动和攻击行为在遭遇熟悉或陌生异性鼠时有差异,但雌雄鼠的友好行为均无显著差异,暗示黄毛鼠是多配制,但需...     

Interactions between overlapping multimale groups of black and white colobus monkeys (Colobus guereza) in the Kakamega Forest,Kenya

Sixteen out of 18 groups of black and white colobus monkeys, or guerezas (Colobus guereza), observed in the Kakamega Forest, Kenya, included more than one adult male. Each group overlapped in its home range with 4–7 other groups, and no group appeared to have exclusive access to any part of its home range. Groups were engaged in intergroup encounters one-quarter of observation time. Encounters often occurred around preferred feeding sites as different groups were attracted to such sites in their overlapping home ranges. Wins and losses during encounters were not dependent on location and a null model suggested that groups were not increasing their encounter rate to defend boundaries, further demonstrating a lack of territoriality. Although guerezas have repeatedly been described as a territorial species living in one-male groups, nonterritorial multimale groups are common in continuous forests. Territorial one-male groups may be usual in narrow riparian forests where resources are limiting, groups are small, and defendability is high, but such organization cannot be regarded as typical of the species. Habitat affects group size, as well as the potential for territoriality, and group size determines the number of adult males per group; therefore, classifying groups as one-male or multimale appears to be an artificial dichotomy. © 1996 Wiley-Liss, Inc.     

Paternity analysis of alternative male reproductive routes among the langurs (Semnopithecus entellus) of Ramnagar

Because primate males usually invest very little in offspring, male reproductive success will mainly be determined by access to fertile females with differences in access leading to differential male reproductive success. To determine the outcome of alternative male reproductive routes, we investigated a wild population of Hanuman langurs at Ramnagar, South Nepal, where groups were either one-male or multimale. Paternity was established by DNA analysis from faeces for 42 infants in five groups. In one-male groups all infants were sired by the only resident male in the group. In multimale groups the alpha male fathered significantly more infants (57%) than all other resident males. Nonresident males sired at least 21% of all infants born into multimale groups. Because of the lower mean number of infants sired by alpha males during their whole tenure as alpha compared with males in one-male groups (2.3 versus 6.8) and the higher maximum value (8.9 versus 6.0), the alpha male route is considered the riskier option. Based on demographic data we suggest that the considerable variance in short-term reproductive success might not translate to the same degree into differences in long-term reproductive success. Copyright 2001 The Association for the Study of Animal Behaviour.     

根田鼠的熟悉性及其自然动情下的配偶选择

报道了在室内雌鼠自然动情条件下根田鼠两性个体配偶选择的3种熟悉性效应的5组实验结果,包括雌性对熟悉和陌生雄鼠、配偶和陌生雄鼠、配偶和熟悉雄鼠的择偶行为实验 , 雄性对熟悉和陌生雌鼠、配偶和陌生雌鼠的择偶行为实验。在实验前, 将1对性成熟的雌雄鼠 (非亲缘关系) 每天关养8 h 共8 d 建立熟悉性; 配对雌雄鼠至少生育1胎则为配偶关系。在 Y 形迷宫内的30 min 实验中, 两个被选择鼠分别以项链拴在横跨选择箱顶端中央的一根铁丝上, 限制它们在各自箱内活动; 而允许异性选择鼠从中立箱自由进入两个选择箱。记录选择鼠对异性被选择鼠的访问、社会探究、攻击、交配和友好行为的频次和时间。经Wilcoxon 关联样本 T 检验发现, 除交配行为不显著外, 雌性根田鼠均选择熟悉性较高的雄鼠; 而雄鼠不具这种选择性。该结果提示雌雄根田鼠的不同择偶行为也许就是反映该种婚配制度特征的直接行为过程。因此, 在择偶行为中, 雌性根田鼠表现的单配性倾向和雄鼠的多配性倾向, 只能以其婚配制度为一雄多雌制的假设来解释。我们的实验还说明在多配制田鼠中, 一雄多雌制与混交制在雌鼠择偶行为上是不同的, 而与单配制的相似或相近, 故简单地比较多配制与单配制则不能反映田鼠亚科动物婚配制度的多样性。     

Reactions of adult and immature squirrel monkeys to intergroup exposure

Initial encounters between unfamiliar animals raise the practical problem of controlling aggression and provide the opportunity to examine changes in social structure that may occur as groups merge. Social interactions and spatial grouping patterns were examined in newly formed squirrel monkey groups, in which a subgroup of familiar adults was introduced to a subgroup of familiar immature squirrel monkeys. Yearlings (10–11 months) and subadults (20–50 months) generally remained spatially distinct from adults, and intergroup interactions often consisted of adult-initiated antagonism. Adults exhibited sexual segregation in their spatial grouping patterns and interactions, whereas yearlings and subadults generally showed sexual integration. These data suggest that there is considerable adult resistance to integration of unfamiliar immatures into established adult social groups. Zoo Biol 17:519–524, 1998. © 1998 Wiley-Liss, Inc.     

Individual participation in intergroup contests is mediated by numerical assessment strategies in black howler and tufted capuchin monkeys

Asymmetries in resource-holding potential between opposing groups frequently determine outcomes of intergroup contests. Since both numerical superiority and high intergroup dominance rank may confer competitive advantages, group members should benefit from assessing the relative strength of rivals prior to engaging in defensive displays. However, differences in individual assessment may emerge when cost–benefit trade-offs differ among group members. We examine the influence of numerical superiority and intergroup dominance relationships on individual participation in intergroup encounters in black howler monkeys (Alouatta pigra) and tufted capuchin monkeys (Sapajus nigritus). Black howlers responded with longer vocal displays during encounters with neighbours with an equal number of resident males, while tufted capuchins increased their participation with increasing relative male group size. Within each species, males and females responded similarly to varying numerical odds, suggesting that despite pay-off asymmetries between males and females, both sexes were similarly influenced by numerical asymmetries in deciding to participate in collective group defence. Whereas the outcome of contests among tufted capuchins was determined by relative male group size, reflected in a pronounced intergroup dominance hierarchy, the absence of dominance relationships among black howler groups may have provoked prolonged vocal displays in order to assess rival groups with matching competitive abilities.     

Group extinction and fusion in free-ranging vervet monkeys

Three cases of group fusion were observed among vervet monkeys in Amboseli National Park, Kenya, during the 1984 drought. In all cases, group fusion involved the migration of at least two females into a small neighboring group. Following migration, the females' natal groups ceased to exist. Although migrants initially assumed low ranks, none received high rates of aggression, and two rose in rank 6 months after their arrival. Migrant females appeared to employ a number of “strategies,” including grooming, allomothering, participation in intergroup encounters, and the formation of coalitions against males and each other to hasten integration. Results suggest that the causes of male and female migration differ fundamentally, and that group fusion occurs primarily in response to the inability of small groups of females to compete successfully with other groups for resources.     

Integration of New Males into Four Social Groups of Tufted Capuchins (Cebus apella)

We examined how aggressive, affiliative, and sexual behavior function to integrate male capuchins (Cebus apella) into a new social group. Nine males were exchanged among four social groups. We performed instantaneous scans and all-occurrence sampling during baseline, introduction, and follow-up periods. The study included three different introduction situations: 1) males familiar to one another were introduced to a group with no other adult male, 2) males unfamiliar to one another were introduced to a group with no other adult male, and 3) males familiar to one another were introduced to a group with an existing elderly, resident male. Severe aggression occurred in situations 2 and 3, but the introductions were peaceful in situation 1. In all cases proceptive females were among the first individuals to affiliate with the males, and males did not appear to compete for access to proceptive females. Following their period of proceptivity, the females that had cycled remained preferred social partners for the males. Immature animals also quickly affiliated with the new males, and the males tolerated the attention from immatures. Affiliative relationships between the males and nonproceptive females developed slowly, and while male-female aggression was mild, aggression among adult males (familiar and unfamiliar) had the potential to be severe.     

One-male groups and intergroup interactions of mountain baboons

The behavioral ecology of mountain baboons, Papio ursinus,cuts across the traditional dichotomy between savannah and desert baboons, providing fresh opportunities to examine socioecological relationships. Mountain baboons were studied at a site where covariation in altitude and group size helps to clarify the influence of ecology on social behavior. One-male groups and lone males were regularly found in the highest-altitude zones. In encounters with multimale groups, a one-male group retreated; the group’s single male attacked his females, herding them far away from the multimale group. The male himself then approached and watched (and often loud-called at) this group. In a two-male group, the younger male herded the females, while the older sometimes defended the group. One-male groups did not show regular, stable aggregations, but two such groups seasonally coordinated their ranging “in tandem.” Ecological explanations for these behaviors and their relationship to the behavior of hamadryas baboons are evaluated, and a new theory of the origin of one-male groups in baboons is developed.     

Increased Frequency of Intergroup Encounters in Wild Bonobos (<Emphasis Type="Italic">Pan paniscus</Emphasis>) Around the Yearly Peak in Fruit Abundance at Wamba

Intergroup interactions in primates vary from nonagonistic to severely aggressive. Food resources and fertile females cause intergroup aggression when groups defend resources and mates from other groups. Peaceful intermingling during intergroup encounters is rare but has been reported in several primates, including bonobos (Pan paniscus). Although intergroup encounters in bonobos occur at both nonprovisioned and provisioned sites, provisioning may be one factor responsible for frequent intergroup encounters. We studied intergroup encounters between one bonobo group (PE) and its neighboring groups, one semihabituated and two habituated groups, under nonprovisioned conditions in 2010–2015 at Wamba, Democratic Republic of Congo. We examined whether fruit abundance and females with sexual swellings influenced encounter frequency. PE group encountered the other groups on 7.1 days (mean, range: 0–19) per month. Up to four different groups met simultaneously at one location. Encounter frequency was highest around the yearly peak in fruit abundance, suggesting that reduced food competition is linked to increased encounter frequency. During periods of relatively low fruit abundance, the probability of an encounter was higher when a higher number of adult females with maximum sexual swellings were present, suggesting that the attractiveness of females with sexual swellings promoted group encounters during periods of relatively low fruit abundance. These findings suggest that both competition for food and the availability of females with sexual swellings influence encounter frequency in bonobos.     

Social organization in the dusky-footed woodrat (Neotoma fuscipes): A field and laboratory study

The dusky-footed woodrat has been characterized as solitary and asocial. In this research I sought to determine some of the parameters of woodrat social organization. In the field, I live trapped, marked and released members of a distinct group of woodrats at bi-weekly intervals from February to June. Twenty-two residents were identified and 21 out of 34 houses were found to be occupied. Visiting occurred regularly, most often at non-occupied houses. Males were unlikely to be visited at their house and were more likely to visit occupied houses than females. Females were visited at home and visited each other. In June the population was removed to the laboratory where paired encounters with familiar and unfamiliar woodrats were used to examine the effect of sex and familiarity on social interactions. Both females and males interacted little with familiar same sex conspecifics, with the behaviour of one member of such pairs being very inhibited. Females with strange females were more interactive and spent more time in contact. Neither sex clearly differentiated between familiar and strange conspecifics of the opposite sex. Males were agonistic or affiliative in encounters with females. The type of response was consistent for a given male, and females responded differently to the two types. It is concluded that woodrats differentiate between same sex conspecifics and show sufficient individual variability to make individual recognition possible and adaptive.     

The effects of familiarity and group size on mating preferences in the guppy,Poecilia reticulata

Abstract In recent years, it has become evident that frequency dependence in the attractiveness of a particular phenotype to mates can contribute to the maintenance of polymorphism. However, these preferences for rare and unfamiliar male phenotypes have only been demonstrated in small, controlled experiments. Here, we tested the preference for unfamiliar mates in groups of six to 96 individuals over 13 days, in the guppy (Poecilia reticulata). We observed individual behaviour in situ to test whether fish discriminate two unfamiliar individuals among many familiar ones. We found that unfamiliar males and females were preferred over the familiar fishes in all groups and that this effect decayed over time. Increasing group sizes and levels of sexual activity did not hamper the preference for unfamiliar mates, providing further support for the role of frequency dependent mate choice in the maintenance of trait polymorphism in natural populations.     

Male dispersal in a provisioned multilevel group of Rhinopithecus roxellana in Shennongjia Nature Reserve, China

Most Old World monkeys show male-biased dispersal. We present the first systematic data on male dispersal in a provisioned multilevel group of Rhinopithecus roxellana, based on 4.5 years of field observations in Shennongjia National Nature Reserve, China. We evaluated both ultimate (inbreeding avoidance and male mating competition) and proximate (food availability and predation risk) factors influencing male dispersal. The focal group contained 34-53 individuals, in 3-4 one-male units (OMUs) and 1 all-male unit (AMU). We observed 37 dispersal events involving 10 of 11 adults, 7 of 8 subadults, and 7 of 15 juveniles. Most interunit transfers within the focal group occurred around the months of mating season. Adult males competed for the leader positions of OMUs mainly through aggressive takeovers, and young males transferred from the OMUs to the AMU at the median age of 41 months, forced out by leader males. No young males older than 4 years remained in natal or non-natal OMUs. The male mating competition hypothesis was supported. The young males emigrated voluntarily from the focal group at the average age of 58.6 months, and no young emigrating male was observed to return, suggesting inbreeding avoidance also played a role in the dispersal of young males. Most emigration/immigration events were parallel dispersal and occurred during intergroup encounters, suggesting increased predation risk during the dispersal period. Males were more likely to emigrate/immigrate during the months when preferred foods were most available. We compared the dispersal patterns in R. roxellana with those in gelada baboons and hamadryas baboons, both living in multilevel societies. Similar to R. roxellana, young male geladas disperse at puberty, but they may return and breed in their natal groups. Males in hamadryas also disperse, but much less commonly than in R. roxellana. Provisioning may have influenced results, and confirming studies on unprovisioned groups would be valuable.     

Responses to Femoral Gland Secretions by Visually Adept Male and Female Collared Lizards

Although visually transmitted social signals are well documented in many diurnal iguanians, including collared lizards, secretory femoral glands also suggest a role of chemical signals in intraspecific communication. We conducted laboratory trials to test the extent to which male and female collared lizards responded by tongue‐flicking femoral gland secretions, neutral (water), and odoriferous (cologne) control substances, males distinguished self‐secretions from those produced by unfamiliar rival males, and females distinguish secretions from unfamiliar vs. familiar males. Both males and females spent similar amounts of time in four arena quadrants each with a Petri dish treated with one of the four test compounds. Males gave more tongue flicks/trial to secretions produced by unfamiliar rivals and cologne than they tongue‐flicked their own secretions and water. By contrast, the number of tongue flicks by females on control substances and familiar and unfamiliar males was similar. Results support the hypothesis that femoral gland secretions function in intrasexual signaling among male collared lizards, perhaps allowing them to distinguish unfamiliar rivals. Females tongue‐flicked secretions from familiar and unfamiliar males with similar frequency that was high relative to that of males, suggesting a possible role of secretions in assessment of males. Ours is the first evidence of a signaling role of femoral gland secretions in collared lizards and adds to a growing body of evidence that chemical signaling has evolved in diurnal lizards that also have highly developed visual‐based signaling.     

Ethological study of the social behavior of hybrid baboons betweenPapio anubis andP. hamadryas in free-ranging groups

The male-female and male-male interactions of hybrid baboons betweenPapio anubis andP. hamadryas were analyzed quantitatively in two free-ranging groups in the Awash Valley, Ethiopia. Morphologically, one group (the Kerrayu group) was closer to hamadryas, while the other (the Gorge group) was closer to anubis. The adult males were classified into four categories; i.e., leaders of one-male units, males in pair units (both in the Kerrayu group), males with a closer appearance to hamadryas, and males with an anubis-like appearance (both in the Gorge group). These categories coincided with the morphological gradient from hamadryas to anubis. Social behavior was described in terms of 53 kinds of behavioral elements identified. In both groups, the closer a male was to being hamadryas in morphology, the more frequent was the aggressive behavior it tended to address toward partner females. The patterns of male-female interactions were compared between one-male units and pair units in the Kerrayu group. In one-male units, females responded immediately with obedient behavior to the males' behavior of directing visual attention toward them. In pair units, females responded with affinitive or avoiding behavior to physical contact by males. The flow of male social behavior was resolved into transitions from one behavioral element to another, and the succession rates for all the observed transitions were independently computed within each male category. By comparing the principal pathways of the behavioral sequences between male categories, 31 “basic pathways” were identified, which were presumed to be common to bothP. anubis andP. hamadryas. The basic pathways were composed of four main behavioral categories, i.e.,Contact, Visual-spacing, Aggressive behavior toward females, andAppeasing behavior toward males. In one-male units, transitions fromVisual-spacing toAggressive behavior were clearly recognized, whereas the principal pathways in pair units lacked such transitions. The frequency distributions of behavioral elements among the above behavioral categories were compared among the four male categories. The more prevalent anubis characters were in morphology, the larger was the proportion thatContact behavior occupied in the total amount of social behavior. The more prevalent hamadryas characters were, the larger was the proportion thatVisual-spacing behavior occupied. The leaders of one-male units showed a higher percentage ofAggressive behavior than did males of the other three categories. A conspicuous difference was observed in the percentage ofAppeasing behavior between the Gorge and Kerrayu groups. It appeared that the high frequency ofAppeasing behavior among males in the Kerrayu group contributed to the spatial cohesion of this group. The similarities of morphology, principal pathways, and frequency distribution of behavior were calculated for every combination of the four male categories. The morphological similarities correlated best with the similarities of principal pathways. It is concluded that the sequential structure of the male social behavior was strongly correlated with the genetic background, while the frequency of social behavior itself was subject to factors other than innate behavioral tendencies, such as the characteristics of the social environment and social context.