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First published online February 15, 2006
Journal of Experimental Biology 209, 927-937 (2006)
Published by The Company of Biologists 2006
doi: 10.1242/jeb.02046
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Cutting corners: the dynamics of turning behaviors in two primate species

Brigitte Demes1,*, Kristian J. Carlson1 and Theresa M. Franz2

1 Department of Anatomical Sciences, Stony Brook University, NY 11794-8081, USA
2 Interdepartmental Doctoral Program in Anthropological Sciences, Stony Brook University, NY 11794-8081, USA


Figure 1
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  		Fig. 1. Dynamics of turning. A turn requires a sideward translation (A) and a rotation that aligns the animal with the new direction of movement (B). The cartoons at the bottom depict the forces that are capable of accomplishing these positional changes. They are mediolateral forces for the translation, and mediolateral and/or fore/aft forces for the rotation.

 

Figure 2
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  		Fig. 2. Experimental setup to record turning forces. Animals either walked on a wooden runway and were forced by two obstacles to turn (A), or they walked on PVC pipes with a gap that forced them to turn (B). The force platform is the rectangle in the center of the runway.

 

Figure 3
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  		Fig. 3. Mediolateral peak reaction forces (as body weight units) on the forelimbs (A) and hindlimbs (B) of the ring-tailed lemurs performing turns of 20° and 45°. Medially directed reaction forces are negative, laterally directed reaction forces are positive in A and B.

 

Figure 4
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  		Fig. 4. Magnitude of peak average peak medial and lateral reaction forces for L. catta (left) and E. patas (right). The asterisks indicate significantly higher medial reaction forces for any particular limb. A laterally directed reaction force was never registered for hindlimb contacts of the female patas monkey. FL, forelimb; HL, hindlimb.

 

Figure 5
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  		Fig. 5. Vertical and mediolateral (m–l) average peak reaction forces for the fore- and hindlimbs of L. catta (left) and E. patas (right). The asterisks indicate significantly higher hindlimb than forelimb forces.

 

Figure 6
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  		Fig. 6. Polar plots of substrate reaction force vectors in the frontal plane. Each arrow represents an individual reaction force with the arrow length representing its magnitude in body weight (BW) units, and arrow orientation its deviation from vertical. SRF vectors leaning medially have negative angles, those leaning laterally have positive angles. E. patas forelimb (A), L. catta forelimb (B), E. patas hindlimb (C), L. catta hindlimb (D).

 




© The Company of Biologists Ltd 2006