Meeting Abstract
The head houses both visual and vestibulocochlear organs that allow an organism to balance, orient, and navigate during locomotion. Maintaining a stable head should be especially important in primates because they walk predominately on compliant substrates in complex arboreal environments. However, the degree to which the head, neck, and trunk remain stable during arboreal walking in primates is unknown. This study tests the hypothesis that the neck helps maintain head stability by mediating the movement of the trunk. We predict that the trunk should have the greatest range of pitch, the head should remain relatively stable with the least pitch, and the neck should have an intermediate range of pitch between that of the trunk and head during walking. In addition, the neck should move opposite the trunk to maintain the position of the head. Three shaved and marked individuals of Varecia variegata were filmed during arboreal and terrestrial quadrupedalism. Markers were digitized using DLT data viewer. Linear mixed models were conducted to account for both variations in stride length and repeatedly measuring the same individual. Results show mixed support for the predictions. During arboreal locomotion, the trunk pitches significantly more than the head and neck. However, the head has a 10o range of pitch while the movement of the neck is negligible. The head is at its inferior-most position at touchdown during arboreal quadrupedalism but moves much less during terrestrial walking. This suggests that the movement of the head is related to visually ensuring substrate position, which is more variable in an arboreal environment. While head stability is required for all types of locomotion, head mobility may be more important when walking on compliant, unpredictable substrates. Supported by NSF BCS-1731142.
