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Silverback Urugamba has Died

January 25, 2013

Silverback Urugamba Has Died

Inkumbuza sits by Urugamba's bodyThe Dian Fossey Gorilla Fund staff are very sad that we must report the death of silverback Urugamba. He was the leader and only silverback in his small group of just seven gorillas and was always known for his peaceful demeanor.

After our field staff found Urugamba very weak in his nest yesterday, a team including staff from the Fossey Fund, RDB (Rwanda park authority), and Gorilla Doctors went to assess his condition first thing this morning. Occasionally, silverbacks are able to make a full recovery on their own, and we hoped that Urugamba might have improved overnight. We were sad to learn that when the team reached him this morning he was already dead.

We cannot say yet what caused Urugamba’s death. He appeared to be in good health on Wednesday when he was visited by trackers and researchers. His sudden illness caught us all by surprise. A necropsy will be performed by Gorilla Doctors and we hope to have some closure when we can better understand the cause of his death.

Unfortunately, the recovery of Urugamba’s body has not yet happened. To gather the best information, it is always best to recover the body as soon as possible to avoid further decomposition. However, in the past we have learned that gorillas seem to get some comfort from confronting the bodies of group members who have died. For example, after dominant silverback Titus died, members of his group remained with the body for two days. We do not want to further stress the group by removing the body too soon. Moreover, premature removal of the body might cause the gorillas to disperse and make it more difficult for us to track them in the coming days.

Today, the members of Urugamba’s group went to look for food in the morning but returned to the body in the afternoon. They rested within seven meters of the body. In fact, sub-adult male Inkumbuza, who used to be able to succeed in getting Urugamba to play with him, as well as juvenile male Igisubizo, both touched and groomed the body. Bishushwe, who had a particularly close relationship with Urugamba even when they were still in Shinda’s group, sat close to the body and looked at it for about one minute, though she did not touch it. The opportunity to observe gorilla behavior after the death of a dominant silverback is rare, and we are humbled to be able to watch Urugamba’s group cope with his death.

Urugamba, June 2012Urugamba was a young silverback, just 21. Born into the group Dian Fossey named Group 5, he followed his mother Kubina when she joined Shinda’s group after the death of dominant silverback, Ziz. After Shinda’s death in November 2008, the group began to split and rejoin, a process that eventually ended with the gorillas permanently splitting into Ntambara’s group and Ugenda’s group in February 2009. Initially, Urugamba followed Ugenda, but eventually left with females Bishushwe and Pasika and their infants in January 2010.

Urugamba never acquired any other females, but Pasika and Bishushwe both weaned their infants and went on to give birth again, allowing the small group to grow gradually. Now the group consists of the two females and their infants; a juvenile male, Igisubizo; and subadult male, Inkumbuza, who is known for transferring back and forth between Urugamba and Ugenda’s groups since their split in 2010.

Because there are no other mature males in the group, the females will eventually have to find a silverback to join. Pasika and Bishushwe are certainly experienced enough to move around the forest and find food, but they cannot protect themselves and their offspring from lone silverbacks or other groups. The two infants, particularly Bishushwe’s infant, Amatwara, who just turned 1 in November, are now very vulnerable to infanticide by an unrelated silverback.

Urugamba's group, still together on the day of his deathThe lone silverback Gwiza has been known to interact with Urugamba’s group in the past. If he is in the area, he may well attempt to take over leadership of the group. Lone silverback Twizere also ranges in the area sometimes and has interacted with the group in the past. Of all possible outcomes for Urugamba’s group, the best chance for the two infants would be for the group to merge with Ugenda’s group, perhaps if subadult male Inkumbuza, who transfers frequently between the two groups, leads the rest of the group to Ugenda. Ugenda’s group and Urugamba’s group have interacted many times since their split, but always peacefully. It appeared usually to be a kind of reunion, with the females clearly loyal to one silverback or the other. If the females try to rejoin Ugenda, since he is already familiar with them and their infants, he may be less likely to commit infanticide. An unrelated silverback, on the other hand, would almost surely kill the infants in order to bring the females back into estrus and sire his own offspring.

Fossey Fund staff are all very concerned for the group, especially the infants, whom we have been monitoring since their birth, but of course we must let the gorillas determine their own path without human interference. We will be collecting behavioral data daily to see how the group responds to Urugamba’s death and how they will find a new silverback to lead them. Urugamba’s group was one of only two single-male groups Fossey Fund currently monitors, so this is an important and unique opportunity to learn about gorilla behavior under these circumstances.