16.04.2021 - 22:04
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Gorillas (conducted by Martha Robbins)

Gorillas are fascinating animals to study because they live in a wide variety of environments, they have a flexible social system, and they are one of our closest living relatives. Gorillas live in a broad diversity of habitats in ten Central African countries, ranging from coastal lowland forests to the high altitude, afromontane rainforests.  They live in cohesive social groups that typically consist of one or more silverback (adult male), several adult females, and immature offspring. There are two species of gorillas, western gorillas (Gorilla gorilla) and eastern gorillas (Gorilla beringei). Each species has two subspecies. Despite their wide distribution, all four subspecies of gorillas are critically endangered, meaning they are at risk of going extinct. A major goal of the gorilla group at the MPI-EVAN is to understand the causes and consequences of variability in ecology, behavior, life histories, and population dynamics of gorillas.

Our main project is the Bwindi Gorilla Project, located in Bwindi Impenetrable National Park, Uganda, where we have been researching mountain gorillas since 1998 [see more about the Bwindi Gorilla Project here]. This is the second longest running research project on habituated gorillas. Our other main project is the Loango Gorilla Project, studying western gorillas in Loango National Park, Gabon [see more about the Loango Gorilla Project here]. This project has been running since 2005 and we have been making systematic behavioral observations one group of habituated gorillas since 2014 [see more about Loango here]. We have collaborative projects with several other field sites including the Karisoke Research Center run by the Dian Fossey Gorilla Fund International and the Mbeli Bai Project in the Republic of Congo run by the Wildlife Conservation Society.  Lastly, we run a conservation education program (BACEP: Bwindi Ape Conservation Education Partnership in collaboration with the North Carolina Zoo and Cleveland Metroparks Zoo), working with four primary schools located on the edge of Bwindi [see more about BACEP here].

Specific Research Topics Include:

Social Behavior

Living in social groups involves both costs and benefits revolving around feeding competition, cooperation, affiliation, and reproductive strategies. Gorillas are particularly interesting species to examine the causes and consequences of social behavior because of the variability environments they inhabit, the high level of reproductive competition among males, and their variable grouping patterns. The main research questions we address are:
 How do gorillas cope with the various costs and benefits of living in cohesive social groups?
 How do differences in diet influence the social relationships and nutritional intake of group members?
 What reproductive strategies are used by males and females?


Life History Strategies

The gorilla group focuses on the factors that shape the variability in life history events, grouping patterns, and reproductive success in gorillas. Gorillas are interesting species to examine life history strategies because they have the fastest reproductive rates of any extant ape and both males and females have flexible dispersal patterns. Through various collaborative projects, we have worked with demographic datasets for three populations of gorillas that each span more than 20 years with each containing more than 300 individuals: the Virunga Volcanoes, Bwindi, and Mbeli Bai.
The overarching questions we address are:
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 (e.g. population structure and growth rates)?


Feeding Ecology

Food resources vary in time and space, resulting in animals needing to adopt strategies to maximize their foraging efficiency within changing environments. How animals respond to the abundance and distribution of food resources in their environment has implications for many key elements related to survival and reproduction including patterns of habitat utilization, group compositions, and social interactions, and population dynamics.
How do differences in food availability influence variability in the diet and nutritional ecology of gorillas living in different habitats?
How are patterns of habitat utilization influenced by food availability and dietary patterns?