24 - Facial Differences Between Rats Selected for Tame and Defensive Aggressive Behaviors, Lab Rats, and Wild-caught Rats

Poster Board Number: 24
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Abstract Body : To test the effects of domestication (i.e., selection for tame behaviors) on facial morphology, our study compares adult brown rats (Rattus norvegicus) selected for tameness and defensive aggressive behaviors to laboratory rats used for general experiments without regard for behavior and wild-caught museum specimens. We hypothesize that: 1) rats selected for tameness will share traits with laboratory rats that, though not selected for tame behaviors, are accustomed to human handling; and 2) defensive aggressive and wild-caught museum specimens will be distinct in their facial morphology from all respective groups in our sample. Our dataset comprises 83 micro-computed tomography (micro-CT) images of adult Rattus norvegicus crania, including 29 specimens selected for tameness, 16 selected for defensive-aggression, 12 lab specimens and 26 wild-caught specimens. We used 33 3D landmarks to capture the facial morphology and analyzed the landmarks using geometric morphometrics and principal component analysis (PCA). Results of the PCA show the tame and wild-caught rats to be the most distinct from one another along PC 1 (24% variance), with the selected defensive aggressive and laboratory rats overlapping along this axis. PC 2 (15.9% variance) separates the laboratory rats from all the other groups and also captures the within-group variation in our sample. Our results reject our first hypothesis and suggest that rigorous selection for tameness alters the facial morphology in particular ways. Interestingly, the laboratory and defensive aggressive rats share some facial similarities, indicating that the latter potentially maintains some wildtype traits present in the laboratory rats. Overall, our findings demonstrate that selection for tame/domesticated behaviors changes the facial skeleton in distinct ways.
Funding: Cobb Professional Development Grant