Personality, subjective well-being, and vocal communication in captive male western lowland gorillas

Although there have been studies on the meaning or function of gorilla vocalizations, they have focused on correlations between calls and basic activity states. If gorilla vocalizations, like human speech, provide information that is both semantic and emotional, then we can expect to get a richer understanding of the meaning or function of gorilla vocalizations by looking at the novel association between an individual's personality and its vocal profile (i.e. the types of calls predominantly given). Personality drives and channels behavior and is therefore a higher level of analysis than basic activity states. Four hypotheses are tested in this dissertation: 1) Personality predicts behavior in captive gorillas; 2) Personality predicts vocal behavior (i.e. the vocal profile) in captive gorillas; 3) Personality predicts subjective well-being in captive gorillas; 4) Subjective well being predicts vocal behavior (i.e. the vocal profile) in captive gorillas. To test these hypotheses, I used behavioral observation and personality and subjective well-being questionnaires on eight male gorillas (five silverbacks; three blackbacks) at the Sedgwick County Zoo in Wichita, Kansas. The personality questionnaires used a modified top-down approach, i.e. a modified five-factor model used in human personality studies. A principle components analysis of the mean personality ratings revealed three components: dominance; extraversion/agreeableness; conscientiousness. This is the first study to document a conscientiousness factor in gorillas which was previously thought to exist only in chimpanzees and humans. There were 16 significant correlations between personality and behavior with an average r value of 0.76. Subjective well-being did not predict behavior with the exception of contact aggression (r=0.71). Extraversion/Agreeableness was significantly positively correlated with subjective well-being and dominance was significantly positively correlated with ability to achieve goals. Neither personality nor subjective well-being predicted vocal rate. Contrary to previous reports, the gorillas in this study did not vocalize at a significantly different rate from wild mountain gorillas. This is the first study to document individual vocal profiles of gorillas, which have implications for captive management. Implications of the "singing" and rhythmic multiple grunt vocalizations for the origins of music and language are discussed.