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Who’s in charge? Lone silverbacks fight for a group

Field staff at the Dian Fossey Gorilla Fund are witnessing an unusual situation among the mountain gorilla groups we monitor, which are normally led by one adult male silverback. Changes in leadership – called dominance – happen from time to time in various ways. Sometimes it can be due to the death of the dominant silverback but at other times a solitary silverback can intrude and pose a challenge, usually by getting one or more females to transfer to him.

Silverback Urugwiro

But in recent weeks, we have been observing a situation where a lone silverback – named Kubona – arrived in a group and seemed to take over from the dominant silverback, Urugwiro. Both of these silverbacks are fairly young, with Kubona at 16 and Urugwiro at 17 years old. And they were born and raised in the same group, called Pablo’s group. In 2014, they each left their natal group and eventually became solitary silverbacks, living independently without a group.

In 2017, Urugwiro managed to form a group of his own, by gaining two females from other groups. Kubona also managed to gain a female but his liaison lasted only a few days. He tried several more times to gain females but was not successful.

Then, on March 28 of this year, our staff saw Kubona interacting with Urugwiro, which started with a violent fight and injuries to both silverbacks. After that fight, Kubona seemed to have won the rights to be with the two females, displacing Urugwiro from his dominant position. For many days, the situation then stayed calm and Urugwiro stayed on the periphery of the group. After a month, he left and became solitary again.

But, just as we decided to re-name the group after Kubona, Urugwiro reappeared, on April 24.  Although Kubona chased him off, it’s possible that Urugwiro may not be ready to give up just yet.

Solitary males are very interesting, because they usually have an ambitious personality, compared to those who remain in their natal groups and work more toward cooperation and group cohesiveness. So observing two lone silverbacks vying to lead a group is a noteworthy occurrence.

“It is always interesting to observe lone silverbacks trying to strategize while challenging a group,” says Veronica Vecellio, the Fossey Fund’s gorilla program senior advisor. “We were glad that the conflict between Urugwiro and Kubona seemed to end without serious consequences. We hope things remain peaceful and can’t wait to see when one of the females gives birth – and to determine who the father is!”

Silverback Kubona with female Bukima