Paper Type

Master's Thesis


College of Arts and Sciences

Degree Name

Master of Science in Biology (MS)



NACO controlled Corporate Body

University of North Florida. Department of Biology

First Advisor

Dr. Quincy Gibson

Second Advisor

Dr. Terry Maple

Rights Statement

Third Advisor

Dr. James Gelsleichter

Department Chair

Dr. Cliff Ross

College Dean

Dr. George Rainbolt


Based on recognized life history traits and ecology, zoos strive to house their gorillas (Gorilla gorilla gorilla) in mixed-sex groups with one mature male or silverback, multiple females, and their offspring. However, successful captive breeding programs and a nearly 50:50 birth sex ratio has created the need to house surplus males in solitary conditions or all-male groups. It is commonly believed that male western gorillas will not tolerate one another in the presence of females; however, multi-male, mixed-sex groups have been observed in the wild. For this reason, some zoos have begun experimenting with this scenario. At the time of data collection, only four of the 51 institutions housing gorillas in the North American Species Survival Plan® population housed multi-male, mixed sex groups. Chapter one documents the activity budgets of two of these multi-male groups and compares them to those of two traditional family troops. Overall behavior repertoire was similar between group type, though more locomoting and aberrant behaviors were exhibited by individuals in the multi-silverback groups. Interaction between the silverbacks varied greatly between the multi-male groups which suggests there could be multiple models of success for these groups. However, further insight is needed to determine why some multi-male groups are successful while others are not. Therefore, the second chapter outlines the results of a multi-institutional survey which covered the recent history of multi-male, mixed-sex groups in North American zoos. The goal of the survey was to determine potential factors associated with silverback compatibility. Results indicate that there is an association between successful multi-male, mixed-sex groups and some life history factors including the relatedness of the males, their rearing histories, and the time at which they were introduced. This research offers insight into a potential gorilla social assemblage that has been underutilized in zoo settings.