Captive Lowland Gorillas Research Articles

Cardiac disease is linked to adiposity in male gorillas (Gorilla gorilla gorilla).

Cardiac disease is a major cause of morbidity and mortality for adult gorillas. Previous research indicates a sex-based difference with predominantly males demonstrating evidence of left ventricular hypertrophy. To evaluate these findings, we analyzed serum markers with cardiac measures in a large sample of gorillas. The study sample included 44 male and 25 female gorillas housed at American Association of Zoo and Aquariums (AZA)-accredited zoos. Serum samples were collected from fasted gorillas during routine veterinary health exams and analyzed to measure leptin, adiponectin, IGF-1, insulin, ferritin, glucose, triglycerides, and cholesterol. Cardiac ultrasonography via transthoracic echocardiogram was performed simultaneously. Three echocardiographic parameters were chosen to assess cardiac disease according to parameters established for captive lowland gorillas: left ventricular internal diameter, inter-ventricular septum thickness, and left ventricular posterior wall thickness. Our data revealed that high leptin, low adiponectin, and lowered cholesterol were significantly and positively correlated with measures of heart thickness and age in males but not in females. Lowered cholesterol in this population would be categorized as elevated in humans. High leptin and low adiponectin are indicative of increased adiposity and suggests a potential parallel with human obesity and cardiovascular disease in males. Interestingly, while females exhibited increased adiposity with age, they did not progress to cardiac disease.

ASSESSMENT OF SERUM 25-HYDROXYVITAMIN D CONCENTRATIONS IN TWO COLLECTIONS OF CAPTIVE GORILLAS (GORILLA GORILLA GORILLA)

Serum 25-hydroxyvitamin D concentrations were assessed in subadult to adult captive lowland gorillas ( Gorilla gorilla gorilla) (n = 26) at two institutions with different husbandry and management practices. Serum 25-hydroxyvitamin D (25[OH]D) concentrations for gorillas managed predominantly indoors was low (14.2 ± 5.9 ng/ml), despite consuming commercial biscuits fortified with vitamin D3. Concentrations of 25(OH)D in gorillas with near daily outdoor access were significantly higher than gorillas managed indoors, although many individuals still had serum values below concentrations recommended for adult humans. Consideration should be given to assessing 25(OH)D concentrations in all captive gorillas and providing specific supplementation, particularly to juveniles without access to direct sunlight.

Benefits of training/playing therapy in a group of captive lowland gorillas (Gorilla gorilla gorilla)

AbstractAnimal well-being and enrichment continue to gain importance in the maintenance of primates living in captivity. Positive reinforcement training (PRT) and/or playing interaction have been shown to be effective in improving the well-being of several species of primates. This research study evaluated the effects of applying a combination of these two techniques (training/playing therapy) on a group of lowland gorillas(Gorilla gorilla gorilla). The effects of this combination on the behaviour of captive primates have been given very little attention to date. The behaviour of a group of seven females was recorded in two different phases at Barcelona Zoo: before (periods 1 and 2) and after (periods 3 and 4) a series of changes were made to the composition of this social group. In each period, two phases were distinguished: i) baseline condition, after the subjects became used to the researcher, focal recordings were made of the group's regular behaviour and, ii) experimental condition, the training and playing sessions (‘gorilla play’) with two specific subjects began one hour before the group went to the outdoor facility. The frequency and duration of the behaviour observed in each of the recording conditions were compared. The results showed positive changes in the gorillas’ behaviour: stereotypies, interactions with the public, aggression between subjects and inactivity were all reduced, while affiliative behaviour and individual and social play-related behaviour increased. Moreover, the benefits of this therapy were observed in trained individuals and the rest of the gorillas in the group, which would seem to indicate that training/playing can be used to create a more relaxed atmosphere, reducing social tension and improving the well-being of all the subjects involved.

Peaceful Post‐Conflict Interactions between Aggressors and Bystanders in captive lowland gorillas (Gorilla gorilla gorilla)

We observed a colony of lowland gorillas in order to assess the occurrence of Peaceful Post-Conflict Interactions between Aggressors and Bystanders (PPIAB). We compared the dynamics of PPIAB with those of Peaceful Post-Conflict Interactions between Victims and Bystanders (PPIVB), which are directed toward victims. We confirmed the occurrence of PPIAB (mean Triadic Contact Tendency: 41.7%+/-16.2% SEM) at frequencies comparable to PPIVB. Immature gorillas were responsible for most PPIAB. PPIAB occurred when the bystander was unrelated to either the aggressor or the victim, and when it was a relative of the aggressor. However, affinitive contact rates were higher in the former case. Unlike PPIVB, PPIAB significantly reduced the likelihood of further aggressions within the group, suggesting that they work at an immediate level. Our data also suggest that bystanders decide when a peaceful contact may be too risky; in fact, neither PPIAB nor PPIVB occurred after high-intensity aggressions.

Response of captive lowland gorillas (Gorilla gorilla gorilla) to different housing conditions: Testing the aggression-density and coping models.

Several studies have suggested that primates react differently to spatial reduction. In this article, the authors tested some general hypotheses on primate response to spatial reduction by studying the Apenheul lowland gorillas (Gorilla gorilla gorilla; Apeldoorn, the Netherlands). The frequency of conflicts did not greatly change between the 2 housing settings, thus not supporting the density- aggression model. Indoor, gorillas performed touching behavior more often and increased their level of reconciliation. These findings support the coping model. Indoor, the gorillas also maintained broader interindividual distances by increasing the levels of sitting alone, avoidance, and dismissing behaviors. In conclusion, the Apenheul gorillas modified selectively the distribution of some patterns typical of their behavioral repertoire in response to a high-density condition. Both avoidance and coping tactics were used, thus revealing high levels of behavioral flexibility in this species.

A preliminary behavioral comparison of two captive all-male gorilla groups.

Gorillas live in polygamous harem groups, generally composed of one male, several adult females, and their offspring. With an equal numbers of male and female gorillas born in captivity, however, housing gorillas in social breeding units inevitably means that some males will not have access to female social partners. Thus, the future of the captive gorilla population depends on the collective ability of zoos to house equal numbers of males and females. This study examined the behavioral profiles of two all-male groups of captive lowland gorillas (Gorilla gorilla gorilla) to provide information on this type of housing situation. One group consisted of three subadult individuals, while the other consisted of two subadults and a silverback. Data were collected during two 6-month intervals, for a total of 284 hr. The behavioral profiles of the animals were stable over the course of the study but proximity patterns changed. Differences in feeding, solitary play, and object-directed behavior were found between groups, while no significant differences were observed in affiliative or agonistic social behavior. At both institutions, group cohesion appeared to be high, particularly between subadults; these individuals spent approximately 10% of their time engaging in social behavior and 25-50% of their time in close proximity (within 5 m). However, the Zoo Atlanta males spent significantly more time within 1 m and 5 m of each other than the Santa Barbara males, which may reflect a higher level of cohesiveness among members of the Zoo Atlanta group. The behavioral profiles of the animals in this study were similar to those found in bachelor groups of wild mountain gorillas. One notable exception was the absence of homosexual behavior between the silverback and subadults in Santa Barbara and the low frequency of this behavior between subadults in both groups. Although more longitudinal data are needed, these data suggest that all-male groups can be a feasible housing strategy for males at certain periods of their life span. Zoo Biol 20:27-40, 2001. Copyright 2001 Wiley-Liss, Inc.

Reproductive monitoring of free-ranging female mountain gorillas by urinary hormone analysis.

Frequent urine samples from three habituated free-ranging adult female mountain gorillas were collected during a four-week period in order to characterize, by analysis of urinary hormones, their ovarian cycle, and to diagnose pregnancy. A conceptive cycle and two cycles that did not result in full term pregnancy were monitored. Behavioral and physiological observations of mating and labial swellings were correlated to urinary hormone results. Mating occurred on days with elevated estrogens. Labial swelling was maximum near or at peak estrogen levels. Pregnancy was diagnosed at the field site by measurement of chorionic gonadotropin using commercially available human pregnancy detection kits. In one pregnancy, gestation length was 254 days. The pregnanediol glucuronide concentrations of the mountain gorilla did not change during the nonconceptive cycle. During the conceptive cycle, the concentrations did not increase until the approximate time of implantation. This finding suggests marked differences in steroid production or metabolism between the mountain gorilla and the captive lowland gorilla.

Body mass in lowland gorillas: a quantitative analysis.

Body proportions and tissue composition (e.g., relative contributions of muscle, skin, bone, and adipose to total body mass) were determined through dissection of four adult captive lowland gorillas. The relative contribution of bone varies little among the four animals (10.2-13.4%) despite considerable range in body weights (99.5-211 kg). In tissue composition, three animals have on average 37.3% muscle relative to body mass. Maximum estimates of body fat range between 19.4-44%. Differences in age, sex, and life history events partially explain the observed variation in body proportions and tissue composition among the four animals. Although gorillas are considered extremely sexually dimorphic in body weight and canine size, differences in tissue are not as dramatic as body mass differences suggest. This study found sex differences mostly in the upper body; males have relatively heavier forelimbs, including heavier deltoid, trunk-binding, and deep back muscles compared to the younger female. The old, obese female had one half the muscle tissue of the other three animals (16% vs. 37.3%), and twice the body fat (44%); forelimbs and upper body musculature were relatively well-developed to compensate for the restricted hip-joint movement due to arthritis. Data on the variation in tissue composition and body proportions in gorillas provide a basis for comparison with other hominoids, including humans. For example, compared to highly dimorphic orangutans, gorillas have more muscle, less adipose tissue, lighter forelimbs and heavier hindlimbs. Such analyses complement studies of the skeleton and contribute to our understanding of human evolution and adaptation.

A review of nutritional and motivational factors contributing to the performance of regurgitation and reingestion in captive lowland gorillas ( Gorilla gorilla gorilla)

Regurgitation and reingestion (R/R) is a common phenomenon in captive lowland gorillas ( Gorilla gorilla gorilla), but it has never been reported in wild populations. Although changes in diet have been shown to reduce the behavior, little is known about the underlying mechanisms that lead to its development and maintenance. In this paper, a comparative analysis of ruminatory behavior in humans and stereotypic behavior in captive, domesticated animals reveals several nutritional and motivational factors that may contribute to the sustained performance of this behavior in captive gorillas. Additional research is needed to evaluate temporal, seasonal, gustatory, social, individual, and medical influences on this behavior.

Paternity determination in captive lowland gorillas and orangutans and wild mountain gorillas by microsatellite analysis

Paternity exclusion studies provide useful information for testing certain theories of behavioral ecology and for the management and conservation of both wild and captive populations of endangered species. This study used eight human nuclear microsatellite loci, in the absence of species-specific PCR primers, to genetically identify the sires of 12 captive lowland gorillas (Gorilla gorilla gorilla) and 2 captive orangutans (Pongo pygmaeus pygmaeus andPongo p. abelii). Parentage assignments were confirmed by excluding all except a single potential sire for each offspring with the least two loci. Sire-offspring relationships were verified in 12 of the 14 cases, and reassigned in the case of two gorilla offspring. The orangutan paternity typing was supplemented by DNA fingerprinting. Additionally, five of the eight microsatellite loci, in conjunction with behavioral data, were used for a non-exhaustive set of paternity exclusions for five wild mountain gorillas (Gorilla g. beringei). The eight loci described in this study should be useful additions to the tools available for the study of genetics in the great apes.

Representation of Action Through Iconic Gesture in a Captive Lowland Gorilla

Alors que l'on dit souvent que seuls les chimpanzes ont un langage gestuel, l'etude des gestes iconiques (mouvement d'un individu suscitant l'action d'un second individu selon la volonte du premier) chez les gorilles du zoo de San Francisco revele neuf types de gestuelles : le toucher a proximite, la petite tape, le mouvement de tete, tapoter la poitrine, balancer les bras sous soi, serrer les bras sont des gestes silencieux exigeant l'attention preexistante de l'« interlocuteur » alors que frapper la poitrine ou tout autre objet sont produits pour attirer l'attention. Ces gestes ont ete analyses en fonction des contextes

Behavioral effects of changing group membership among captive lowland gorillas

Group membership was modified among 4 gorilla groups at Zoo Atlanta in an attempt to increase compatibility and sexual behavior. The modifications ultimately moved 7 adult females among the groups. The moves were made by individually introducing the new group members to the old members, resulting in 18 total introductions. Several individual and social behaviors differed in the two conditions. The most obvious change was a temporary increase in aggressive display behaviors, as well as an increase in contact and social examination, in the postmovement condition. Additionally, the individual behaviors of travelling and eating increased after the introductions, while resting decreased. Other self-maintenance behaviors did not change. Finally, there was an increase in time mothers and offspring spent closer to one another following the moves. Previous research and anecdotal evidence suggest that gorillas respond to changes in group membership with aggression; these data support and extend those data to different age/sex groups, postmovement trends in behavior, and other aspects of gorilla behavior. © 1996 Wiley-Liss, Inc.

Behavioral effects of changing group membership among captive lowland gorillas

Group membership was modified among 4 gorilla groups at Zoo Atlanta in an attempt to increase compatibility and sexual behavior. The modifications ultimately moved 7 adult females among the groups. The moves were made by individually introducing the new group members to the old members, resulting in 18 total introductions. Several individual and social behaviors differed in the two conditions. The most obvious change was a temporary increase in aggressive display behaviors, as well as an increase in contact and social examination, in the postmovement condition. Additionally, the individual behaviors of travelling and eating increased after the introductions, while resting decreased. Other self-maintenance behaviors did not change. Finally, there was an increase in time mothers and offspring spent closer to one another following the moves. Previous research and anecdotal evidence suggest that gorillas respond to changes in group membership with aggression; these data support and extend those data to different age/sex groups, postmovement trends in behavior, and other aspects of gorilla behavior. © 1996 Wiley-Liss, Inc.

A preliminary study of the effects of ecologically relevant sounds on the behaviour of captive lowland gorillas

This exploratory study evaluated the effects of ecologically relevant sounds on captive lowland gorillas ( Gorilla gorilla gorilla), housed in the night quarters adjacent to their new exhibit at the San Diego Zoo. The behaviour of four western lowland gorillas was sampled using remote videotaping under each of four noise conditions associated with captive housing (quiet, ventilation on, bonobo vocalization playbacks and caretaker sounds) and each of two sound conditions (rain forest sounds ‘off’, rain forest sounds ‘on’). Significant differences in behaviour across noise conditions were found; these differences were ameliorated for infants, but only partially for adults by the rain forest sounds. The two adults responded to the rain forest sounds with increased agitation. The preliminary nature of these results is discussed.

Preference for structural environmental features in captive lowland gorillas (Gorilla gorilla gorilla)

AbstractIncreased interest in the behavioral effects of captive environments and advances in zoo design have resulted in a proliferation of “naturalistic” animal habitats. Although scientists have demonstrated that such exhibits have some positive effects on behavior, very little is known about the complex relationships between these specialized environments and behavior. This study sought to determine preferences for structural environmental features, such as slope and trees, exhibited by captive lowland gorillas (Gorilla gorilla gorilla). An average of 496 location scans were collected on each of 23 gorillas, housed in 6 groups. The results indicate that enclosure usage was significantly associated with the features of slope, nearness to holding facility, and presence of environmental components additional to substrate (e.g., tree or rock). In particular, areas with flat ground that were near the holding building and that included at least one component additional to substrate were preferred by all animals. © 1993 Wiley‐Liss, Inc.

Deception and hiding in captive lowland gorillas (Gorilla gorilla gorilla)

Deception and hiding are described for a group of captive lowland gorillas comprising two adult males, one female, and her infant. The males repeatedly interacted with the infant, and their interest was repeatedly thwarted by the mother. As in other social situations in which one animal controls access to an object desired by another, deceit was used to thwart the other's control. Either one or both males at times concealed their actions toward the infant, inhibited their attention to the infant, created a neutral image to get the infant, or interacted with the infant to tease the mother.

Handedness for Eating in Gorillas

Observations of spontaneous reaching for food in 31 captive lowland gorillas found a full range of hand preferences between strong left and strong right, with most animals showing intermediate levels of preference. There was a high degree of consistency between observa tions made on different occasions for the same animal, showing that degrees of relative preference tend to be stable in individuals. The findings agree with the majority of previous studies of apes and other primates in showing no species bias to one side, with about half the animals left and half right preferent.

Typhlitis Due to Balantidium coli in Captive Lowland Gorillas

Typhlitis caused by Balantidium coli and requiring surgical resection occurred in three captive lowland gorillas over a 30-month period. Not one of the other gorillas in the colony or their keepers was ill. B. coli is distributed widely geographically and widely among mammals. Asymptomatic commensalism predominates, but invasion of the colonic mucosa can produce diarrhea and dysentery and set the stage for local or systemic spread.

Sex differences in the behaviour of immature captive lowland gorillas

Studies of the behaviour of 26 (12 males and 14 females) captive infant and juvenile lowland gorillas showed clear sex differences. Females showed greater interest in young infants and were more active in nest building as well as in solitary and social grooming. Males were more active in locomotive, dominance, and aggressive behaviour and in social play. Hand-rearing further increased aggression. Males were more aggressive when they lived with only one partner, and they rose in rank even above older females, a pattern that has not been observed in naturally reared gorillas.

Serological evidence for variation in the incidence of herpesvirus infections in different species of apes

Sera from captive lowland gorillas, chimpanzees, orangutans, and gibbons were screened by enzyme-linked immunosorbent assay (ELISA) for antibody to herpesviruses serologically related to human herpes simplex virus types 1 and 2 (HSV-1, HSV-2), a baboon virus (SA8), and a macaque herpesvirus (B virus). The incidence of herpesvirus antibodies varied considerably among the different species, gorillas having the highest incidence of seropositivity (65.4%) and orangutans the lowest. The virus specificity of positive sera was further analyzed by examining the kinetics of virus neutralization, competition of reactivity in ELISAs, and immunoblotting against HSV-1, HSV-2, SA8, and B virus antigens. Using these assays, the majority of positive gorilla sera (49 of 53, 92%) were determined to react in a manner identical to human HSV-1 immune sera. The remaining four positive gorilla sera reacted as HSV-2-positive sera. In contrast, the majority of positive chimpanzee sera (5 of 7, 71%) reacted as HSV-2 immune rather than HSV-1 immune. All positive sera from gibbon apes reacted as HSV-1 positive. No orangutan sera were identified which gave positive reactions by ELISAs to any of the four primate herpesviruses tested. Although four orangutan sera gave equivocal results against HSV-1 antigen, further analysis by immunoblotting could not confirm any specific reactivity with any of the primate herpesvirus antigens. Varied reactivity among individual animals with both SA8 and B virus proteins was observed, but none of the seropositive primates detected appeared to be infected with either of these simian viruses. Three gorilla sera had antigen recognition patterns slightly different from those of HSV-2-positive human and chimpanzee sera and another HSV-2-positive gorilla serum, raising the possibility that these animals harbor an indigenous virus related to HSV-2.