Abstract # 6166 Poster # 104:

Scheduled for Thursday, June 18, 2015 06:00 PM-08:00 PM: (Cascade AJBCD) Poster Presentation


ELO-RATING AS A TOOL TO MEASURE RANK CHANGES AND DOMINANCE STABILITY IN SEMI FREE RANGING RHESUS MACAQUES

L. J. Wooddell1,2, S. K. Kaburu1,2,3, A. M. Dettmer1,2 and S. J. Suomi1,2
1PO Box 529, Dickerson, MD 20837, USA, 2Laboratory of Comparative Ethology, Eunice Kennedy Shriver National Institute of Child Health and Human Development, 3Dipartimento di Neuroscienze, Università di Parma, Parma, Italy
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     Rhesus macaque (Macaca mulatta) society is generally considered a stable linear hierarchy in which individuals inherit maternal rank and very seldom change in dominance, except when younger sisters grow to outrank their older sisters. However, in a group of approximately 80 semi-free ranging rhesus macaques at the NIH Laboratory of Comparative Ethology field station, we have anecdotal evidence of revision in dominance resulting from major events, such as the death of high ranking females, significant fights, and temporary removal from the field for medical treatment. A relatively new method of assessing dominance in animals, Elo-rating, uses sequential interactions to constantly update ratings and has been proposed to both track changes in dominance over time and measure rank stability, which typical matrix based models cannot readily do. We tested the hypothesis that our anecdotal evidence of major events could be mapped onto Elo-rating results to pinpoint the circumstances for dominance fluctuations. We generated Elo-ratings for 84 individuals based on 2,027 opportunistically observed dyadic interactions between February 2013 and January 2015. We analyzed the Elo-ratings surrounding N=24 major events and found that the ratings significantly changed after these events (Z=-2.286, p=0.022). These results address the prevailing assumption of stability in rhesus macaque society by offering a new tool for tracking changes in dominance rank over time.