Pioneering research in gorilla behavior

We have a guest blogger for this posting! Our intrepid Primate Cognition Intern, Liam Kelly, has prepared a summary focusing on bachelor groups of gorillas. Fascinating stuff, taking place right here at Zoo Atlanta. See below, and enjoy!

– Joe Mendelson, PhD, Director of Research

Some of the most impressive individuals here at Zoo Atlanta are the western lowland gorilla (Gorilla gorilla gorilla) silverbacks. Silverbacks are adult male gorillas, so named for the silver saddle coloration on their backs upon reaching maturity. They can be nearly twice the size of their female counterparts and are significantly stronger. Here at Zoo Atlanta, our gorilla population includes seven silverbacks and three soon-to-be silverbacks. I know—a lot of testosterone in one place! Currently, there are five different groups with silverbacks in them: a geriatric group, family group and three bachelor groups.

If you didn’t know, bachelor groups are a relatively new in zoological settings. Zoo Atlanta played a critical role as one of the pioneers of researching, creating, implementing, and sustaining bachelor groups in zoos. In the years before the Zoo pioneered this area, one male would be the leader of a group of females, while the other males would have had to live alone. The earlier school of thought was that adult male gorillas were to be separated from other males due to fear of serious and possibly lethal aggression toward one another. The multitude of solitary male gorillas became an issue with the sex ratio of gorillas being approximately 50:50.

Bachelor groups of gorillas do exist in the wild, although they seem to not exist for particularly long periods of time. Zoo Atlanta has since become a leader in the care of bachelor social groups. Primate researchers, including myself, have collected and continue to collect important behavioral data on these groups to continually better understand the dynamics of all-male groups for their feasibility and sustainability.

For example, a study conducted here at Zoo Atlanta found nine factors that are important to the success of the formation and maintenance of all-male gorilla groups. These factors include age, relatedness/relationship quality, group composition, number of males per group, rearing history, personality, the presence of females and habitat design (Stoinski et al, 2004). In 2018, we now have multiple bachelor groups of gorillas and are presently caring for three bachelor groups. There are also now zoos across the world that implement and sustain all-male gorilla groups, largely thanks to knowledge gained from Zoo Atlanta’s research and experience.
Liam Kelly
Primate Cognition Research Intern