The Effect of Obstacles and Forelimb Positions on Bipedal Locomotion in Lizards

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Bipedal locomotion has evolved independently in numerous lizard taxa (Clemente, 2014). Initial acceleration, trunk angle, and the posterior shift of the center of mass contribute significantly to bipedal running (Aerts et al., 2003). Recent work indicates that bipedal posture is advantageous during obstacle negotiation. However, the effects of neither obstacle placement, nor forelimb position, have yet to be studied in the context of bipedal locomotion. This study quantified the frequency of bipedalism when running with vs. without an obstacle at 0.8 meters from initiating a sprint. Whether bipedal posture is used at the start of a sprint vs. in the stride preceding the obstacle was also quantified. Additionally, forelimb position during bipedal running and obstacle negotiation will be examined. Two species with contrasting body forms were selected (Sceloporus woodi, Aspidoscelis sexlineata) to assess potential variation in behavioral patterns. Lizards were coerced to run along a 1.4-meter track and filmed with high speed video. Sceloporus woodi ran bipedally at the start of the trial in 77.78% of the trials, regardless of obstacle presence. In the strides approaching an obstacle S. woodi ran bipedally in 72.73% of trials. Aspidoscelis sexlineata ran bipedally at the start of a trial in 50% of trials regardless of obstacle presence. In strides just prior to the obstacle, A. sexlineata ran bipedally in all trials. Data examining forelimb position during bipedal strides will test how forelimb position affects the center of mass and if it may be an applied strategy for navigating obstacles.


Society for Integrative and Comparative Biology Annual Meeting (SICB)


New Orleans, LA