Socioecological factors influencing intraspecific variation in ranging dynamics of western lowland gorillas (Gorilla gorilla gorilla) in Ndoki Forest.

Ranging dynamics are physical and behavioral representations of how different socioecological factors affect an organism's spatial decisions and space use strategies. Western lowland gorillas (Gorilla gorilla gorilla) are a model species to investigate the drivers of spatial dynamics based on both the natural variation in socioecological factors within the species and compared with their mountain gorilla counterparts. In this study, we evaluate the influences of resource seasonality and social dynamics on variation in home range size, utilization, and intergroup overlap among multiple gorilla groups over an 8-year study period in the northern Republic of Congo. This study shows that western lowland gorillas can have small home ranges comparable to mountain gorillas, rather than universally larger home ranges as previously supposed, and that home ranges are stable through time. The largest source of variation in space use was the degree of intergroup home range overlap. The study groups did not demonstrate intraspecific variation in range size nor changes in intergroup overlap with respect to seasonality of fruit resources, but all groups demonstrated expansion of monthly range and core area with group size, matching predictions of intragroup feeding competition. These findings highlight the potential impact of intergroup relationships on space use and prompt further research on the role of social dynamics in ranging strategies. In this study, we reveal a greater degree of variability and flexibility in gorilla ranging behavior than previously realized which is relevant to improving comparative studies and informing conservation strategies on behalf of these endangered primates.

Long-term observations in the Ndoki forest resolve enduring questions about truffle foraging by western lowland gorillas.

While there is growing recognition of the importance of traditional knowledge in science, these perspectives remain underrepresented in research publications. However, the synthesis of these approaches has tremendous potential to improve our understanding of wildlife and ecosystems. Toward realizing this aim, we combined local traditional knowledge with molecular classification techniques to investigate "soil scratching" behavior in western lowland gorillas in two localities in Republic of Congo, the Goualougo Triangle and the Djéké Triangle. Daily observations of four gorilla groups for nearly a decade revealed that soil scratching is a foraging strategy to access a deer truffle species, identified here as Elaphomyces labyrinthinus. We also conducted group scans to calculate the time gorillas spent foraging for deer truffles and video focal observations to assess foraging efficiency. There was considerable variation in soil scratching across groups. It was most common in Buka's group, followed by Kingo's group and Mététélé's group. Truffle foraging was rarely observed in the Loya-Makassa group. While the overall distribution of deer truffles seemingly determines the occurrence of this behavior across populations, we found indications of social influences on soil scratching within populations. For example, an adult female transferred from a group in which the behavior was rare to another group where it is common and adjusted her frequencies of soil scratching to that of her new group. Finally, these findings were included in an ecological impact assessment of the Djéké Triangle that prompted conservation managers to shift the location of tourism-associated construction to safeguard this putative cultural behavior.

Predictors of respiratory illness in western lowland gorillas.

Infectious disease is hypothesized to be one of the most important causes of morbidity and mortality in wild great apes. Specific socioecological factors have been shown to influence incidences of respiratory illness and disease prevalence in some primate populations. In this study, we evaluated potential predictors (including age, sex, group size, fruit availability, and rainfall) of respiratory illness across three western lowland gorilla groups in the Republic of Congo. A total of 19,319 observational health assessments were conducted during daily follows of habituated gorillas in the Goualougo and Djéké Triangles over a 4-year study period. We detected 1146 incidences of clinical respiratory signs, which indicated the timing of probable disease outbreaks within and between groups. Overall, we found that males were more likely to exhibit signs than females, and increasing age resulted in a higher likelihood of respiratory signs. Silverback males showed the highest average monthly prevalence of coughs and sneezes (Goualougo: silverback Loya, 9.35 signs/month; Djéké: silverback Buka, 2.65 signs/month; silverback Kingo,1.88 signs/month) in each of their groups. Periods of low fruit availability were associated with an increased likelihood of respiratory signs. The global pandemic has increased awareness about the importance of continuous monitoring and preparedness for infectious disease outbreaks, which are also known to threaten wild ape populations. In addition to the strict implementation of disease prevention protocols at field sites focused on great apes, there is a need for heightened vigilance and systematic monitoring across sites to protect both wildlife and human populations.

Path To Acceptance and Refined Practices for Habituating Western Lowland Gorillas.

Although western lowland gorillas (Gorilla gorilla gorilla) are the most numerous and widespread gorilla subspecies, they have remained relatively unstudied. International tourism has been initiated at several sites in the Congo Basin, which necessitates habituation of gorillas to human presence. However, habituation has proven difficult due to several obstacles, including relatively low population densities, small group sizes, and thick understory vegetation. In this article, we propose refinements to current approaches to habituating western lowland gorillas that maximize safety and emphasize adaptive responses based on empirical evidence. In addition to reviewing published reports, our approach is informed by the recent habituation of the Mététélé group in the Djéké Triangle, an area that was recently included in the Nouabalé-Ndoki National Park in Republic of Congo. We evaluate progress in habituation according to time spent in the presence of the gorillas and their reactions to humans. The Mététélé group is composed of 14 individuals and has a home range that overlaps with two habituated gorilla groups. Early in the habituation process, we discovered that three of Mététélé's group members were individuals who had previously been habituated as members of other groups. The presence of these individuals expedited the habituation process. Familiarity with humans may have also reduced aggressive responses during the habituation process. The overall result is a refined step-by-step approach to the habituation of western lowland gorillas that includes procedures and assessments to meet best-practice guidelines and ensure the wellbeing of both gorillas and humans.

Interspecific interactions between sympatric apes.

Gorillas reside in sympatry with chimpanzees over the majority of their range. Compiling all known reports of overlap between apes and augmenting these with observations made over twenty years in the Ndoki Forest, we examine the potential predation-related, foraging, and social contexts of interspecific associations between gorillas and chimpanzees. We reveal a greater diversity of interactions than previously recognized, which range from play to lethal aggression. Furthermore, there are indications that interactions between ape species may serve multiple functions. Interactions between gorillas and chimpanzees were most common during foraging activities, but they also overlapped in several other contexts. From a social perspective, we provide evidence of consistent relationships between particular chimpanzee-gorilla dyads. In addition to providing new insights into extant primate community dynamics, the diversity of interactions between apes points to an entirely new field of study in early human origins as early hominins also likely had opportunities to associate.