Influence of personality, age, sex, and estrous state on chimpanzee problem-solving success
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Despite the importance of individual problem solvers for group- and individual-level fitness, the correlates of individual problem-solving success are still an open topic of investigation. In addition to demographic factors, such as age or sex, certain personality dimensions have also been revealed as reliable correlates of problem-solving by animals. Such correlates, however, have been little-studied in chimpanzees. To empirically test the influence of age, sex, estrous state, and different personality factors on chimpanzee problem-solving, we individually tested 36 captive chimpanzees with two novel foraging puzzles. We included both female (N = 24) and male (N = 12) adult chimpanzees (aged 14–47 years) in our sample. We also controlled for the females’ estrous state—a potential influence on cognitive reasoning—by testing cycling females both when their sexual swelling was maximally tumescent (associated with the luteinizing hormone surge of a female’s estrous cycle) and again when it was detumescent. Although we found no correlation between the chimpanzees’ success with either puzzle and their age or sex, the chimpanzees’ personality ratings did correlate with responses to the novel foraging puzzles. Specifically, male chimpanzees that were rated highly on the factors Methodical, Openness (to experience), and Dominance spent longer interacting with the puzzles. There was also a positive relationship between the latency of females to begin interacting with the two tasks and their rating on the factor Reactivity/Undependability. No other significant correlations were found, but we report tentative evidence for increased problem-solving success by the females when they had detumescent estrous swellings.
KeywordsPan troglodytes Chimpanzees Personality Problem-solving Enrichment Sexual swelling Estrous state
S.A.P. and R.L.K. were funded by a Royal Society Dorothy Hodgkin Fellowship awarded to R.L.K., and at the time of writing, L.M.H. was supported by the Leo S. Guthman Foundation. The chimpanzee colony at the UT MD Anderson facility is supported by a NIH U42 (RR-15090) grant. We also wish to show our appreciation for all the staff at the UT MD Anderson facility for their support and help and for providing the highest level of care for the chimpanzees housed there. In particular, we thank Tyrel McAdams and Ricky Merino for making the required modifications to the two foraging puzzles to make them suitable for use with chimpanzees and Veterinary Technician Jeffrey Haller for providing expert knowledge on the chimpanzee swelling ratings. We are also grateful to Laura Kurtycz for acting as our blind coder, our anonymous reviewers and the journal editor.
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