Thursday, January 12, 2012

A Most Persistent Solitary Silverback


The Fossey Fund’s Karisoke™ Research Center routinely monitors nine groups of mountain gorillas. Ranging in the same area are six well-known solitary silverbacks that make appearances from time to time when they are searching out social groups in hopes of attracting females. By the end of 2011, Karisoke researchers had recorded 82 encounters with a lone silverback, 54 of which were active interactions with a social group. These interactions happened under a variety of different scenarios and lasted anywhere from mere seconds to an entire day, to weeks on end. While these silverbacks are frequently alone, they are almost always on the trail of another group, biding their time to make a move.

The behavior of the lone silverback

Solitary silverbacks spend several years - and sometimes their entire adult life - traveling alone. The young males are born and raised in the safety of a gorilla group, but as they grow into adults and the characteristic silver hair begins to show on their back, the desire to become dominant can cause them to strike out on their own. The silverback will then begin a lonely quest that may last for years, peppered with dramatic interactionss. Throughout that time, the lone silverback will periodically pursue a social group, usually with his eye on a specific female he would like to acquire. Displaying and vocalizing dramatically, he can push the group’s dominant silverback to react aggressively, sometimes resulting in violence or injury. More frequently however, the field staff observes "auditory interactions" between social groups and the lone silverbacks. This occurs when the lone silverback announces his presence with intimidating chest beats and hooting vocalizations, to which the silverbacks within the group will respond accordingly. Sometimes the interaction will end there, if the group is successful in discouraging the outsider.

Will persistence pay off?

Without a doubt, the most tenacious of these six lone silverbacks has been Gwiza, whom Karisoke trackers encountered 31 times in 2011. Gwiza left Shinda’s group in April 2004 when he was 16 years old. During the past eight years he has been observed traveling alone. Interestingly enough, since the death of dominant silverback Shinda and the subsequent group split, Gwiza’s interaction frequency has increased dramatically. The lone silverback routinely targets Ugenda’s and Ntambara’s groups (the two groups that resulted from thebreakup of Shinda's group). It seems that, despite his decision to live and travel alone, silverback Gwiza still does not want to stray too far from his origins....

To read the rest of the latest e News article on the Fossey Fund website, click here

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