22.02.2017 - 02:36
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Gorillas (conducted by Martha Robbins)


Gorillas are found in ten Central African countries, occupying a broad diversity of habitats ranging from coastal lowland forests to the high altitude, afromontane rainforests. Despite their wide distribution, all four subspecies of gorillas are threatened with extinction. In particular, mountain gorillas are most endangered with at least 700 individuals remaining in two isolated populations: the Virunga Volcanoes of Rwanda, Uganda, and Democratic Republic of Congo and the Bwindi-Impenetrable National Park, Uganda.

Gorillas are one of our closest living relatives.  Furthermore, they are an interesting species to study, both in terms of understanding how they have adapted to such a variety of habitats and by providing a excellent opportunity to test many hypotheses of primate behavioral ecology that assume variation in ecology will lead to variation in behavior and demography.   A major goal of current research on gorillas is to understand the causes and consequences of variability in ecology, behavior, life histories, and genetics in differing environments. While most of our knowledge concerning gorillas comes from research conducted on the mountain gorillas in the Virunga Volcanoes, we now have more than 14 years of observation on gorillas in Bwindi Impenetrable National Park, Uganda.  Work on other gorilla populations has mainly focused on their ecology, partially due to the difficulties encountered in habituating western lowland gorillas.  However, in recent years significant progress has been made in studies of other gorilla populations to address their patterns of sociality, feeding ecology, and demography.  Given the importance of comparing different populations, we aim to work in several locations throughout central Africa.  In addition to direct behavioral observations on habituated gorillas, our work also involves vegetation sampling, using fecal analysis to determine diet and/or for genetic analysis, as well as innovative use of motion-sensored video camera ‘traps’.

Specific research topics and questions include:

Feeding Ecology
  • How does seasonal variation in food availability influence the dietary and nutritional intake of gorillas?
  • Do dietary differences among gorilla populations lead to variation in home range size and utilization?
  • How do gorilla ranging patterns vary according to group size, degree of frugivory and other variables?
  • What is the nutritional composition of gorilla food items and how does it vary between gorilla populations?
  • Do gorillas forage efficiently?  Eg. do they alter their ranging patterns according to food availability and caloric intake?
  • Does social rank influence dietary and nutritional intake?
Social Behavior
  • How do differences in diet, specifically an increase consumption of a clumped food resource such as fruit, influence the social relationships of group members?
  • What reproductive strategies are used by males and females?
  • What factors influence the reproductive success of both males and females?
  • What are the hormonal correlates to female reproductive behavior and how does it vary according to female reproductive status?
  • What are the patterns of affiliative relationships among males and females in the short and long term?
Demography and Life Histories
  • How do individual behavioral and demographic factors (eg. dispersal patterns, group size, birth and mortality rates) influence individual reproductive success?
  • How do individual life history variables and environmental factors translate into population level phenomena (eg. population structure and growth rates)?
  • Are the two populations of critically endangered mountain gorillas growing?