Fossey Fund News

May 22, 2013

Musilikale's Split from Pablo Group Succeeding

Musilikale with Itorero, watched by MahaneOn April 4, trackers spotted seven gorillas from Pablo’s group near the group’s nests, but the other 38 members of the group were noticeably absent, only to be located later that day more than 1.5 kilometers away. Pablo’s group is the largest group of mountain gorillas that the Dian Fossey Gorilla Fund International follows in Volcanoes National Park, with 45 members.

Over the next several days Pablo’s group was located, but without the seven gorillas that had been seen far from the group on April 4. Eventually the seven missing gorillas were found, led by silverback Musilikale, who seemed to be leading them farther and farther away from Pablo’s group. At first, Fossey Fund staff were wary of considering the split permanent. According to Gorilla Program Coordinator Veronica Vecellio, “groups temporarily splitting is not that unusual, but permanent splits are much less common.” However, as two months have passed and the gorillas have remained separated, it seems more and more likely that in fact Musilikale has defected from Pablo’s group and successfully formed his own.

Cantsbee, now 34 years old, has been the dominant silverback in Pablo’s group since 1994. Born in 1978, he is one of only three gorillas from Dian Fossey’s time who are still alive, and was featured in the first episode of a 2010 BBC documentary series, “Wildlife.” Pablo’s group includes seven silverbacks and one more male who will reach the age of 12 and silverback status this year. It is not surprising that a subgroup has formed, considering Cantsbee’s old age and the unusually large number of eligible contenders in the group who could either attempt to challenge Cantsbee for dominance or leave to form a new group. However, it is surprising that out of all of the silverbacks in Pablo’s group Musilikale is the one who caused the group’s recent split.

Though Musilikale is Cantsbee’s son, he has always been a peripheral group member, vulnerable to being kicked out, particularly as he has not had the best history with Cantsbee or with Cantsbee’s other son Girucasi, who is the second-ranking silverback in the group. Musilikale has challenged Girucasi on many occasions, though it was not until Nov. 2012 that Musilikale set off his first conflict with Cantsbee. The incident involved Musilikale following Cantsbee apparently too close for his comfort, provoking him to jump on and bite Musilikale. A small brawl ensued and eventually Musilikale was chased away from the group.

On the rare occasions when dominance shifts occur, Vecellio says that “gorillas employ different individual strategies to increase reproductive success and social rank.” With so much potential competition in the group for the spot as dominant silverback, it seems that Musilikale decided he would have a better chance for both reproductive success and social rank by attempting to leave with several females instead of fighting for the coveted top ranking in Pablo’s group.

MusilikaleEven more surprising than Musilikale’s being the leader of this successful split is which gorillas have chosen to follow him: Mahane and three of her offspring: infant Itorero, blackback Ichumbi, and silverback Turakomeje, as well as blackback Noheli, who is the brother of Akamaro, whom Mahane cared for after she was abandoned as an infant when their mother left Pablo’s group.

Mahane has been the dominant female in Pablo’s group for some time and has always been especially close to Cantsbee, the father of her many children, which makes her decision to leave the group highly unusual. Vecellio suspects that Mahane saw an opportunity to live in a smaller group and took it, because “living in a large group is good for protection, but it can be very uncomfortable as far as space is concerned.” According to Vecellio, Mahane’s decision to leave Pablo’s group might also have been motivated by the fact that she is related to Cantsbee, and switching groups to follow an unrelated silverback like Musilikale could offer a good opportunity for a new sexual partner and increase her success in procreation.

Since the split first occurred in April, Fossey Fund researchers and trackers have been following both Pablo’s group and Musilikale’s group closely, as it was still unclear whether they would remain separated. There has only been one interaction between the groups during the two months of their separation. On May 2, trackers found that the six gorillas that were following Musilikale had returned to Pablo’s group, with Musilikale nowhere to be found. However, the reunion was a brief one, as by the next day the six gorillas had left Pablo’s group again, and were not found until May 8, when they were finally spotted with Musilikale far from Pablo’s group’s ranging area. While there is still a chance Musilikale’s subgroup could rejoin Pablo’s group, it is seeming more unlikely by the day.

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