![]() Disease and anthropogenetic threats may disproportionately affect particular age/sex classes that can impact the social grouping patterns. Increased infanticide may limit population growth as male mating competition intensifies. ![]() For example, increased feeding competition may limit the size of groups as a population grows. A change in population density may lead to an increase or decrease in number of groups and/or group size. In addition to its effect on demographic parameters, changes in population density can also influence the social organization of species that live in groups. For example, a growing population will often have a younger age distribution than a declining population. When direct measurements of those demographic parameters are not available, they are sometimes estimated from the age structure to assess the population dynamics. If females are not annual breeders, however, then fertility could decline before offspring mortality. An increase in population density is predicted to affect demographic parameters in the following sequence: higher offspring mortality, followed by a later age of first reproduction, lower female fertility, and ultimately higher adult mortality. One of the most common topics in studies of population dynamics is the density dependence of demographic rates. Other regions with a net influx are considered a “refuge”, if they have higher population density than the surrounding area, which has been found near long-term research stations. In contrast, a “sink” is an area with fewer births than deaths, and a net influx of individuals to sustain its population. Such regions are known as a “source”, and are considered priorities for supporting broader populations. Studies of population dynamics can contribute to conservation management decisions by identifying local regions with more births than deaths and a net outflow of individuals. On a local scale, the proximate causes of variation in population dynamics can include changes in the rates of births and deaths, as well as the influx and outflow of individuals. ![]() In addition to human disturbances, changes in population size and structure can also arise from natural environmental shifts, density dependence, as well as demographic stochasticity. To combat this crisis, a key component to conservation efforts is the monitoring of population dynamics. The results highlight the value of law enforcement, long-term monitoring, and protected areas but they do not diminish the importance of improving conservation for this critically endangered species.Īlong with other taxa, the order Primates is facing an extinction crisis due to habitat destruction, poaching and illegal activities, disease, and climate change. Our results provide evidence of population stability or growth for some western gorillas (albeit within a small area). The distribution of gorillas among age/sex categories also did not change significantly, which suggests that the population had a stable age structure. We found no significant evidence of density dependence on female reproductive success or male mating competition. The average group size did not change significantly during the study, which is consistent with the possibility that western gorillas face socioecological constraints on group size, even when the population is increasing. The influx of gorillas mainly involved immigration of individuals into existing study groups (social dispersal), but it also included the appearance of a few previously unknown groups (locational dispersal). ![]() After adjusting for a net influx of gorillas into the study population, the increase represents an inherent growth rate of 0.7% per year, with 95% confidence limits between -0.7% and 2.6%. ![]() The Mbeli population more than doubled from 101 to 226 gorillas during the study. Here we examine 25 years of population dynamics of western gorillas at Mbeli Bai, a swampy forest clearing in Nouabalé-Ndoki National Park, the Republic of Congo. Long-term studies of population dynamics can provide insights into life history theory, population ecology, socioecology, conservation biology and wildlife management. ![]()
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