Management of respiratory complications in a western lowland gorilla (Gorilla gorilla gorilla) born by cesarean section

A female western lowland gorilla (Gorilla gorilla gorilla) infant was delivered by cesarean section (C‐section) to an 18‐year‐old primiparous dam after prolonged labor. The infant required resuscitation at birth and was hospitalized for management of pneumonia and associated respiratory distress secondary to the aspiration of meconium‐stained amniotic fluid. The infant received nine days of intensive care with respiratory support, antibiotics, intravenous fluid therapy, anti‐inflammatory drugs, bronchodilators, and chest physiotherapy. Respiratory support included nasal continuous positive airway pressure (CPAP), and supplemental oxygen. Complications included right lung atelectasis secondary to bronchial obstruction and pneumonia. Following the resolution of pneumonia, visual reintroductions with the troop were initiated. The dam was given a medical lactation supplement (metoclopramide) and her mammary glands were stimulated to increase milk production. After several days of visual and olfactory introductions, the infant was successfully physically reintroduced to her dam at 12 days of age; the dam showed appropriate maternal response and nursing of the infant. The infant had appropriate growth and development, and 4 years later, has no evidence of negative side effects of neonatal respiratory disease. This is the first reported case of management of neonatal gorilla respiratory disease associated with a C‐section, with successful reintroduction to the family group after hospitalization.     

Fatal ulcerative colitis in a western lowland gorilla (Gorilla gorilla gorilla)

A captive western lowland gorilla (Gorilla gorilla gorilla) presented with watery diarrhoea that progressed to become profuse and haemorrhagic. Faecal analyses revealed Balantidium (B.) coli trophozoites and salmonella-like bacteria. Despite treatment the gorilla died on the 5th day after onset of symptoms. Post-mortem examination revealed a severe erosive-ulcerative superficial and deep colitis. Histological examination of post-mortem samples of the colon showed plentiful B. coli invading into the mucosa and submucosa, whilst PCR screening of bacterial DNA could not confirm any bacteria species which could be connected to the clinical picture. As B. coli is usually a non-pathogenic gut commensal, and as this animal previously showed evidence of non-symptomatic infection of B. coli, it is possible that the switch in pathogenicity was triggered by an acute bacterial infection. Despite successful treatment of the bacterial infection the secondary deep invasion of B. coli was not reversed, possibly because of the failure of the treatment regimen, and led to the death of the gorilla.     

Sex-biased dispersal in western lowland gorillas (Gorilla gorilla gorilla)

We explored two hypotheses related to potential differences between sexes in dispersal behaviour in western lowland gorillas (Gorilla gorilla gorilla). Direct observations suggest that immature females have more opportunities to move between breeding groups than immature males. The distribution of kin dyadic relationships within and between groups does not, however, support this hypothesis. At larger geographical scales, dispersal is likely to be easier for males than females because of the solitary phase most blackbacks experience before founding their own breeding group. However, previous work indicates that males settle preferentially close to male kin. By specifically tracing female and male lineages with mitochondrial and Y-chromosomal genetic markers, we found that male gorillas in the 6000 km2 area we surveyed form a single population whereas females are restricted to the individual sites we sampled and do not freely move around this area. These differences are more correctly described as differences in dispersal distances, rather than differences in dispersal rates between sexes (both sexes emigrate from their natal group in this species). Differences in resource competition and dispersal costs between female and male gorillas are compatible with the observed pattern, but more work is needed to understand if these ultimate causes are responsible for sex-biased dispersal distances in western lowland gorillas.     

Cervical necrotizing fasciitis and myositis in a western lowland gorilla (Gorilla gorilla gorilla)

A 39-yr-old wild-caught, female western lowland gorilla ( Gorilla gorilla gorilla ) died during an immobilization to assess swelling and apparent pain of the cervical region. Necropsy revealed a fistulous tract containing plant material in the oropharynx, above the soft palate, communicating with a left-sided cervical necrotizing fasciitis and myositis. Alpha-hemolytic Streptococcus and Prevotella sp. were isolated from the cervical lesion . This is a report of cervical necrotizing fasciitis in a western lowland gorilla.     

Sexual behavior in female western lowland gorillas (Gorilla gorilla gorilla): evidence for sexual competition

Previous research in gorillas suggests that females engage in post‐conception mating as a form of sexual competition designed to improve their own reproductive success. This study focused on sexual behaviors in a newly formed group of western lowland gorillas (Gorilla gorilla gorilla) housed at Zoo Atlanta. All females engaged in mating outside their conceptive periods, although there was individual variation in the frequency of the behavior. An analysis of the presence/absence of sexual behavior found females, regardless of reproductive condition, were more likely to engage in sexual behavior on days when other females were sexually active. On these “co‐occurrence” days, females were significantly more likely to solicit the silverback, but copulations did not differ from expectation. The results find further evidence for sexual competition among female gorillas and suggest that this may occur throughout their reproductive cycle rather than only during pregnancy. Am. J. Primatol. 71:587–593, 2009. © 2009 Wiley‐Liss, Inc.     

Postconflict behavior in captive western lowland gorillas (Gorilla gorilla gorilla)

Postconflict (PC) behaviors, including reconciliation and consolation, have been observed in many primate and several nonprimate species. Using the PC-matched control (MC) method, PC behavior was examined in two groups (n=13) of captive western lowland gorillas, a species for which no conflict resolution data have been published. Analyses of 223 conflicts showed significantly more affiliation between former opponents after a conflict when compared to control periods, indicating reconciliation. Results also showed significantly more affiliation between the victim and a third-party after a conflict, indicating consolation. Both solicited and unsolicited consolation were observed. The majority of the affiliative interactions observed for both reconciliation and consolation were social proximity, which suggests that unlike most nonhuman primates, proximity, rather than physical contact, may be the main mechanism for resolving conflicts in western lowland gorillas. PC behavior was not uniform throughout the groups, but rather varied according to dyad type.     

Mitochondrial DNA phylogeography of western lowland gorillas (Gorilla gorilla gorilla)

The geographical distribution of genetic variation within western lowland gorillas (Gorilla gorilla gorilla) was examined to clarify the population genetic structure and recent evolutionary history of this group. DNA was amplified from shed hair collected from sites across the range of the three traditionally recognized gorilla subspecies: western lowland (G. g. gorilla), eastern lowland (G. g. graueri) and mountain (G. g. beringei) gorillas. Nucleotide sequence variation was examined in the first hypervariable domain of the mitochondrial control region and was much higher in western lowland gorillas than in either of the other two subspecies. In addition to recapitulating the major evolutionary split between eastern and western lowland gorillas, phylogenetic analysis indicates a phylogeographical division within western lowland gorillas, one haplogroup comprising gorilla populations from eastern Nigeria through to southeast Cameroon and a second comprising all other western lowland gorillas. Within this second haplogroup, haplotypes appear to be partitioned geographically into three subgroups: (i) Equatorial Guinea, (ii) Central African Republic, and (iii) Gabon and adjacent Congo. There is also evidence of limited haplotype admixture in northeastern Gabon and southeast Cameroon. The phylogeographical patterns are broadly consistent with those predicted by current Pleistocene refuge hypotheses for the region and suggest that historical events have played an important role in shaping the population structure of this subspecies.     

Seed dispersal effectiveness of the western lowland gorilla (Gorilla gorilla gorilla) in Gabon

The quantitative and qualitative aspects of seed dispersal by the western lowland gorilla (Gorilla gorilla gorilla) were investigated in Gabon. Fresh faeces were collected and washed to identify and count the seeds. Seed germinability after gut passage was estimated with trials in a nursery at the study site. To assess the impact of gut passage on germination success and delay, comparative trials were run with four treatments: (i) gut passed seeds cleaned of faeces, (ii) gut passed seeds within a faecal matrix, (iii) seeds from fresh fruits surrounded by pulp, and (iv) seeds from fresh fruits cleaned of pulp. The analysis of 180 faecal units resulted in the identification of 58 species of seed. Germination trials were realized for 55 species and the mean germination success reached 46%. The impact of gut passage was investigated for Santiria trimera and Chrysophyllum lacourtianum; both species displayed higher germination success after ingestion. This study shows that gorillas effectively disperse seeds of numerous plant species, many of which provide timber or nontimber forest products or are typical of Gabonese forests. Considering the high‐quality of gorilla deposition sites, gorillas is thought to play a unique role in the dynamics of Central African forest.     

Growth and feeding relationships of a hand-reared lowland gorilla infant (Gorilla g gorilla)

A captive-born female lowland gorilla that was being hand-reared by a group of surrogate mothers in a public zoo was observed for her first 6 mo. Caloric intake and weight gain, along with feeding bias of surrogate mothers, were examined. Caloric intake was highest during early morning and late at night. The weekly caloric intake and weight gain fluctuated with no established pattern. Although the gorilla's caloric intake did not increase with age, her total weight increased with a slower growth rate in the latter part of the study period, indicating a decreased caloric intake/weight ratio. It became evident that each surrogate exhibited an “overfeeding” and “underfeeding” tendency; calories given by the surrogates varied considerably, reflecting the interaction between the infant and the surrogates.     

Food transfers in immature wild western lowland gorillas (Gorilla gorilla gorilla)

The transfer of food items between individuals has been described in primates as serving an informative purpose in addition to supplementing the diet of immature individuals. This behaviour has yet to be described in western lowland gorillas (Gorilla gorilla gorilla), and results are presented here of observations of food transfers in immature gorillas at Mbeli Bai, Republic of Congo. The frequency of food transfers decreased with increasing immature age, while the frequency of independent feeding and processing of food increased. Transfers between mothers and infants were the most frequent, with infants attempting to take items from the mother. These attempts were not always successful and the item was relinquished on less than 50% of attempts. Mothers also took items from their offspring. The results point to the functional significance of food transfers in western lowland gorillas being informational. In a bai environment, where one species forms the majority of a visiting gorilla’s diet despite other species being available, the initiation of food transfers by immatures is proposed to serve the purpose of familiarising them with which species, and which parts of those species, may be eaten.     

Male genetic structure and paternity in western lowland gorillas (Gorilla gorilla gorilla)

The male dispersal patterns of western lowland gorillas (WLGs, Gorilla gorilla gorilla) are not well understood. To determine whether most silverbacks stay close to their relatives, we analyzed autosomal and Y‐chromosomal microsatellites (STRs) in wild WLGs at Moukalaba, Gabon. We obtained STR genotypes for 38 individuals, including eight silverbacks and 12 adult females in an approximately 40 km² area. Among them, 20 individuals were members of one identified group (Group Gentil; GG), including one silverback and six adult females. The silverback sired all 13 of the offspring in GG and no Y‐STR polymorphism within GG was found, as expected in a one‐male group structure. Over all silverbacks sampled, Y‐STR diversity was high considering the limited sampling area, and silverbacks with similar Y‐STR haplotypes were not always located in nearby areas. Although the misclassification rate of kinship estimates in this study was not negligible, there were no kin dyads among all silverbacks sampled. These results suggest that silverbacks born in the same group do not stay close to each other after maturation. The Y‐STR diversity in this study was similar to that of a previous study conducted in an area that was approximately 150 times larger than our study area. Similarity of WLG Y‐STR diversity between studies at different sampling scales suggests that male gene flow may not be geographically limited. These results suggest that WLG males normally disperse from their natal areas after maturation, at least, in Moukalaba. Am J Phys Anthropol 151:583–588, 2013. © 2013 Wiley Periodicals, Inc.     

Spatial memory and foraging competition in captive western lowland gorillas (Gorilla gorilla gorilla)

Spatial memory and foraging competition were investigated in three mother/offspring pairs of western lowland gorillas,Gorilla gorilla gorilla, using a naturalistic foraging task at the Toronto Zoo. Sixteen permanent food sites were placed throughout the animals’ enclosures. All of the sites were baited and a pair of animals was free to visit the sites and collect the food. Five of the subjects collected the food with accuracy better than chance. Most of the subjects visited the sites using a pattern, and for half the subjects this was one of adjacency. The high accuracy of five of the subjects and the lack of a consistent adjacency pattern suggest that the animals did in fact use spatial memory. Furthermore, the gorillas tended to avoid visiting food sites that had been previously depleted by their partner. They also appeared to split their search of the enclosures, each visiting only a proportion of the food sites. This indicated that the animals were competing and altering their foraging behaviour based on the behaviour of their partner. Therefore, accuracy was recalculated to take this into account. When the sites depleted by either animal in a pair during a given trial were worked into the accuracy calculations for individual animals, three of the animals still maintained accuracy above chance. This suggests that the animals were not only able to remember which sites they had depleted, but those sites depleted by their foraging partner as well.     

Nutritional composition of the diet of the western gorilla (Gorilla gorilla): Interspecific variation in diet quality

To meet nutritional needs, primates adjust their diets in response to local habitat differences, though whether these dietary modifications translate to changes in dietary nutrient intake is unknown. A previous study of two populations of the mountain gorilla (MG: Gorilla beringei) found no evidence for intraspecific variation in the nutrient composition of their diets, despite ecological and dietary differences between sites. One potential explanation is that nutritional variability in primate diets requires greater ecological divergence than what was captured between MG sites, underpinning environmental differences in the nutrient quality of plant foods. To test whether Gorilla exhibits interspecific variation in dietary composition and nutrient intake, we studied the composition and macronutrients of the western gorilla (WG: Gorilla gorilla) staple diets and compared them with published data from the two MG populations. We recorded feeding time and food intake of four adult female WGs from one habituated group over a period of 11 months (December 2004–October 2005) at the Mondika Research Center, Republic of Congo, allowing for assessment of seasonal patterns of nutrient intake. Staple diets of WGs and MGs diverged in their dietary and macronutrient composition. Compared to MGs, the staple diet of WGs (by intake) contained higher proportions of fruit (43%) and leaf (12%) and a lower proportion of herb (39%), resulting in a higher intake of total nonstructural carbohydrate and fiber and a lower intake of crude protein. Staple gorilla fruits and herbs differed in nutrient quality between sites. Gorillas exhibit nutritional flexibility that reflects ecological variation in the nutrient quality of plant foods. Since dietary quality typically affects rates of growth and reproduction in primates, our results suggest that interspecific differences in nutrient intake and food quality may shape differences in gorilla nutrient balancing and female life history strategies.