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Comparing golden monkeys and gorillas

The Dian Fossey Gorilla Fund has been studying gorillas in the wild for more than 55 years now, ever since Dian Fossey set up her research in 1967. But it was only in 2004 that we began studying the only other primate that lives in the forest with the mountain gorillas – the golden monkey. That’s when our biodiversity program manager – Dr. Deo Tuyisingize – who was then a University of Rwanda student, began our studies of the golden monkeys, as there was an ongoing plan at the time to habituate two groups that could be studied, monitored and also visited by tourists.

Most of the golden monkey population (about 4,620 individuals) is located in Rwanda’s Volcanoes National Park, where the gorillas live. But there is also a much smaller population, of about 170, that is found in Rwanda’s Gishwati-Mukura park. And thanks to the work that Deo started, we have a growing database of information about the golden monkeys, enough so that we can compare their lives to those of the gorillas.

Eat, mate, sleep

Like the gorillas, golden monkeys are vegetarians and eat a large variety of plant species. However, we’ve found that the golden monkeys in the Volcanoes are leaf-eaters while those in Gishwati are fruit-eaters.

And, with golden monkeys, food availability is related to reproduction – they give birth slightly before or during key food availability and consumption periods. So, unlike the gorillas, who mate all year long, the golden monkeys are seasonal breeders with distinct mating and birthing seasons.

Gorillas carry their infants on their backs as soon as the infants are strong enough, while golden monkeys carry their babies ventrally (close to their chest). 

And, of course, since golden monkeys are monkeys, they have tails while gorillas (and other apes) don’t. 

When it comes to sleeping, gorillas build night nests on the ground while the golden monkeys do not build nests. They spend their nights in tree branches or branches of bamboo.

Gorilla groups vs. golden monkey groups

Gorillas and golden monkeys both live mainly in family groups, which vary in size. But some of the golden monkey groups we’ve observed have been much larger than any gorilla group – up to 180 members! 

And while female gorillas often change groups during their lives seeking the best places to reproduce and raise their young, golden monkey females tend to stay in their groups and form their own hierarchies, while the males move around seeking the best opportunities.

Kudos to Dr. Deo, whose latest research study on the golden monkeys is featured on the cover of this month’s International Journal of Primatology.