Wild Mountain Gorillas Research Articles

Post‐conflict Social Events in Wild Mountain Gorillas (Mammalia, Hominoidea). I. Social Interactions between Opponents

AbstractResearchers have documented elevated rates of affinitive interaction between opponents shortly after aggressive conflicts, or reconciliation, in many primate species. Reconciliation may ameliorate the immediate negative effects of aggression by reducing the chance of further aggression between opponents and thus reducing tension, and may avert or repair damage to long‐term social relationships important to the animals' fitness. Data on post‐conflict interactions between opponents in two groups of wild mountain gorillas(Gorilla gorilla beringei)fail to show reconciliation after conflicts between females, between males, or between immatures, but females seem to commonly reconcile themselves with males after receipt of male aggression. Females and subordinate males often avoid same‐sex opponents after conflicts. Females commonly retaliate against female aggressors, and post‐conflict rates of aggression between females are higher than baseline levels. Females may not need to achieve reconciliation with each other because relationships between co‐resident relatives are resiliant, while those between non‐relatives are mostly neutral to antagonistic. Males are, however, important social partners and protectors of females, and female transfer is common. Thus, the results strongly support the ‘important relationships’ hypothesis for the function of reconciliation.

Post‐conflict Social Events in Wild Mountain Gorillas. II. Redirection, Side Direction, and Consolation

AbstractInevitably, members of primate groups sometimes have aggressive contests with each other. Targets of aggression can engage in several types of interaction with third parties to ameliorate its adverse effects. They can redirect aggression, which may reduce the risk of further aggression from the initial opponents and reduce tension, or they can initiate affinitive interactions with third parties, in order to seek protection or reassurance. They can also receive reassuring acts from them (‘consolation’). Researchers have documented high levels of redirection in many primate species, but consolation is thus far known only in chimpanzees. Data on post‐conflict social interactions between targets of aggression and third parties in two groups of wild mountain gorillas (Gorilla gorilla beringei) show that immatures and subordinate males, but not females, redirect aggression at high rates. Furthermore, immatures seek affinitive interactions with their mothers, and adult females seek them with adult males, at elevated rates. Affinitive interactions between females and males seem mainly to have a protective function and are associated with decreased risks of further aggression between female opponents. Redirection by females after female‐female conflicts may be uncommon because targets commonly retaliate against aggressors. Males may offer females protection and consolation as services, and the results support the argument that such services are important when dominance relationships between females are often undecided and retaliation between opponents is common.

Evidence for an a‐herpesvirus indigenous to mountain gorillas

Sera from wild mountain gorillas were screened for antibodies reactive with primate alpha-herpesviruses. Four of seven individuals tested (58%) were positive. In all four sera the highest titers were to HSV-2 followed by HSV-1 and SA8. Immunoblot analysis confirmed a preferential reactivity with HSV-2 antigen. Further analysis by competition ELISA indicated that these gorillas had experienced infection with a virus antigenically similar but not identical to HSV-2. These results represent the first evidence for an alpha-herpesvirus indigenous in a free ranging, nonhuman anthropoid species.

Reproductive intervals in captive female western lowland gorillas with a comparison to wild mountain gorillas.

A wide disparity between parturition and the resumption of sexual behavior in two captive female western lowland gorillas prompted an investigation of interbirth intervals (IBIs) in captive western lowland gorillas that had reared their infants. To determine reproductive intervals, a questionnaire was sent to 30 institutions (19 in North America and 11 in Europe) that maintained captive females who had previously reared or were currently rearing their offspring. Information compiled relates to the length of reproductive intervals, including lactational anestrus, estrous behavior to conception and from parturition to conception, and IBIs. These data are compared with studies published on wild mountain gorillas. The median IBI for 16 mothers still rearing infants when their next conception occurred was 4 years (range 2.33-6.42 years, N = 16). Twenty-one percent of the 52 mothers in this study are no longer reproducing. The mean time without reproduction since separation from their last offspring was 5.43 years. This study indicates that the length of IBIs, lactational anestrus, and intervals from parturition, separation, and estrous behavior to conception compare closely with findings for wild populations. Incompatibility between partners may be a factor limiting further reproduction in some captive mothers in this study.

Sexual initiation in wild mountain gorillas

A field study of wild mountain gorillas was conducted to elucidate details of sexual initiation required for an interpretation of the increased frequency of copulation during the menstrual cycle, in comparison to the wild, that occurs when this species is tested in traditional laboratory pair tests. Although females in the wild played a clear role in establishing and maintaining proximity to the male and assertively presenting for copulation, all female presenting was preceded by some form of behavior by the male. Of particular relevance were several components of the male’s chest-beat display that had been observed at much higher frequencies in the laboratory tests. Although originally described as male aggression in the laboratory tests, such behavior now appears to be male sexual initiative, elicited by female proximity. The exaggerated form and frequency of the display in the laboratory, and the increased copulation during the cycle that ensued, are likely due to (1) placing females in proximity to a male daily, rather than on 2–3 days of estrus as occurs in the wild, and (2) the inability of the female in the laboratory to withdraw from male proximity during pair tests in a single cage. In addition to clarifying the data on laboratory pair tests, the data on wild gorillas have relevance to the captive breeding of gorillas.

Sex-related behavior of immature wild mountain gorillas.

Sex-related behavior in immature wild mountain gorillas consisted primarily of genital stimulating episodes in which one animal thrusted against the body of another. Whereas the immature males used the D-V position predominantly, a single immature female that performed as an actor used the V-V position exclusively. All episodes of genital stimulating behavior originated in the context of play and most actors were older (and larger) than recipients of such behavior. The data support the findings of earlier research but suggest that genital stimulating behavior among immature gorillas occurs more frequently than previously thought. These results in conjunction with comparable data on pygmy and common chimpanzees and orangutans suggest that genital-stimulating behavior by immature individuals is a species-typical phenomenon in the behavioral development of the great apes.

Composition and variability of mountain gorilla diets in the Central Virungas.

Data are presented here on the feeding ecology of wild mountain gorillas (Gorilla gorilla beringei) which were observed for approximately 2,400 hours over a 17-month period in the Parc National des Volcans, Rwanda. Aspects of the relationship between the composition, diversity, and temporal consistency of the gorillas' diet and spatial and temporal variability in food distribution patterns are described. Mountain gorillas are folivores that show considerable specialization on plant parts, species and families. This pattern is facilitated by the general richness of their habitat. Their environment is heterogeneous, and spatial variability in food distribution is more pronounced than temporal variability. The gorillas rely almost completely on perennially available foliage of herbs and vines. Their diet varies little in association with seasonal factors but varies markedly in space in association with variability in the vegetational composition of the habitat. Individuals in the main study group shared basically similar patterns of food choice. Different groups also shared a similar general pattern, although there were differences in detail that apparently resulted largely from vegetational contrasts between home ranges. The gorillas' behavioral responses to environmental complexity lend general support to recent ideas concerning the evolution of their social system.

Reproduction among free-living mountain gorillas

The current status of wild gorilla populations and observations of reproductive behavior in wild mountain gorillas are described. The entire world population of gorillas is now less than 12,000, of which about 500 are in captivity. Only about 3,000 wild gorillas live in conservation areas. There are 9,000-10,000 lowland gorillas, about 400 eastern lowland gorillas, and only about 220 mountain gorillas. The author observed mountain gorillas for 13 years in the Virunga Volcano region of Zaire, Rwanda, and Uganda. Among adult gorillas, 580 copulations were observed. Most of these were initiated by females. Details of sexual behavior and development in free-living gorillas are presented.

Chimpanzees, Tools, and Termites: Another Example From Tanzania

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Social relationships between adult male and female mountain gorillas in the wild

Social relationships between adult males and females in two groups of wild mountain gorilla are described. Each group contained about five, largely unrelated sub-adult and adult females, a peripheral near-adult male, and one fully mature male. Females were clearly attracted to the dominant male, and those with young offspring spent the most time near him. Also, when a female came into oestrus her time near the dominant male increased temporarily. Not all females engaged in grooming with this male, and those that did were judged to have the less stable, i.e. less potentially long-lasting, relationships with him. The relevance of affinitive behaviour to acquisition of benefits and to establishment and maintenance of relationships, plus the influence of competition on maintenance of relationships are discussed.

The FPS Mountain Gorilla Project—a Report from Rwanda

In February 1978 the story broke in Europe and America of the killing of Digit, a wild mountain gorilla known by millions outside Rwanda through his appearance on television with Dr Dian Fossey, the American zoologist who has been studying gorillas in the Virunga Volcanoes for eleven years. FPS immediately set up an appeal for funds, to protect the gorillas. This was promoted by the Sunday Times and collected nearly £8000, some from school conservation clubs sending all their savings. Encouraged by this splendid response FPS decided to launch a major Mountain Gorilla Project to help Rwanda to guard the gorillas and the Parc National des Volcans. The goal is £50,000.But before this could be launched, FPS, working in close association with WWF, needed up-to-date information on the situation in Rwanda and decided to send a small mission to report. The members were Professor Kai Curry-Lindahl, FPS Vice President, world-renowned scientist and conservationist who has worked in the Virungas at intervals since 1952 and knows the problems, especially on the Zaire side; Dr A.H. Harcourt, Coordinator of the Mountain Gorilla Project, who studied gorillas for two years in the Virungas and knew Digit well, and Brian Jackman, whose story in the Sunday Times on the death of Digit was mainly responsible for the money so far donated. They arrived in Rwanda in early August to be greeted with the news that two more gorillas of Dian Fossey's study groups, including “Uncle Bert”, had been killed. They spent a week on their mission, and extracts from their report to FPS are printed below. Since Sabena Airlines very generously backed the mission, travel expenses were minimal and none came out of the Mountain Gorilla Fund. The following are extracts from the Mission's report.

Coprophagy by wild mountain gorilla

Coprophagy by wild mountain gorilla

Activity Periods and Patterns of Social Interaction: a Neglected Problem

AbstractAnimals tend to divide their days into longish periods of different predominant maintenance activities, such that, for instance, early morning and late afternoon feeding periods are clearly separated by a midday rest period. Frequencies of social behaviour are known to change with change in the predominant activity. As an obvious example, grooming tends to be more frequent during rest periods than when the animals are moving and feeding. However, the possibility that patterns, as opposed to frequencies, of social interaction could change through the day has rarely been mentioned, let alone considered in detail. Data from a two-year field study of wild mountain gorilla, show that patterns of social interaction do indeed change with the predominant maintenance activity : neglect of such variation can lead to, at best, ignorance of interesting facets of behaviour and, at worst, misleading conclusions about the social relationships of the study animals.

The birth of a wild mountain gorilla (Gorilla gorilla beringei)

The live birth of a wild mountain gorilla is described. Details of the birth process are given along with the mother’s periparturitional behaviour and the responses of others to the birth. The mother, a multiparous female, gave no observable indication that birth was imminent, and delivered her infant quickly and easily. During parturition, a subadult male showed interest in the proceedings. Following delivery, several animals approached the mother, who then left the birth site. The mother cleaned her infant and by two hours postpartum had established ventro-ventral contact and, possibly, nursing. These data are related to relevant observations from the literature and unpublished data on other animals from this study.

Male emigration and female transfer in wild mountain gorilla

IN many group-living primates, males leave their natal group and transfer to other groups far more commonly than do females (for example, refs 1–4). For only one species—the chimpanzee—is there good evidence that females leave their natal group and transfer more commonly than do males5,6, but little information has been available on the movements in and out of gorilla groups. The structure of the gorilla population in the Virunga Volcanoes of Zaire and Rwanda7,8 and elsewhere9 indicates that males at least leave their natal group: there are a number of lone males; and many groups contain only one fully adult male, but a number of adult females. Schaller9 implied that males transferred between groups more often than did females. The few data in ref. 10 indicate, however, that only females transfer between groups, although both males and females leave groups. Incorporating data for 8.5 yr from the Karisoke Research Centre in the Virunga Volcanoes (ref. 10 and unpublished results), this paper provides the first extensive evidence that both male and female gorillas leave their natal group, although some sons may remain; that males that leave initially travel alone; and that only females transfer.

Can the Mountain Gorillas Be Saved?

Previous articleNext article No AccessCan the Mountain Gorillas Be Saved?Raymond A. DartRaymond A. Dart Search for more articles by this author PDFPDF PLUS Add to favoritesDownload CitationTrack CitationsPermissionsReprints Share onFacebookTwitterLinkedInRedditEmail SectionsMoreDetailsFiguresReferencesCited by Current Anthropology Volume 1, Number 4Jul., 1960 Sponsored by the Wenner-Gren Foundation for Anthropological Research Article DOIhttps://doi.org/10.1086/200117 Views: 8Total views on this site Citations: 6Citations are reported from Crossref Copyright 1960 Wenner-Gren Foundation for Anthropological Research, Inc.PDF download Crossref reports the following articles citing this article:G. Štrkalj, P.V. Tobias Raymond Dart as a pioneering primatologist, HOMO 59, no.44 (Sep 2008): 271–286.https://doi.org/10.1016/j.jchb.2008.06.002Amanda Rees Reflections on the Field, Social Studies of Science 37, no.66 (Jun 2016): 881–907.https://doi.org/10.1177/0306312707077368Amanda Rees A place that answers questions: primatological field sites and the making of authentic observations, Studies in History and Philosophy of Science Part C: Studies in History and Philosophy of Biological and Biomedical Sciences 37, no.22 (Jun 2006): 311–333.https://doi.org/10.1016/j.shpsc.2006.03.008PHILLIP V. TOBIAS, JOHN E. COOPER The mountain gorilla: A little known chapter of pioneering studies, Transactions of the Royal Society of South Africa 58, no.11 (Jan 2003): 75–77.https://doi.org/10.1080/00359190309519936Goran Strkalj Where was Raymond Dart wrong?, African Studies 57, no.11 (Feb 2007): 107–111.https://doi.org/10.1080/00020189808707888Masao Kawai, Hiroki Mizuhara An ecological study on the wild mountain gorilla (Gorilla gorilla beringei), Primates 2, no.11 (Mar 1959): 1–42.https://doi.org/10.1007/BF01666109