Role of the Tail in Balancing Whole Body Angular Momentum in Kangaroo Rats (D. deserti)
Additional Funding Sources
The project described was supported by a student grant from the UI Office of Undergraduate Research, and by the National Science Foundation under Award No. 1553550.
Abstract
Kangaroo rats (Dipodomys deserti) are bipedal hopping rodents that have a remarkably long tail. Studies have suggested that during bipedal hopping the tail balances angular momentum of the legs and/or body; however, the mechanism is not well understood. Video recordings of desert kangaroo rats show large tail swings during steady state hopping. From these observations, we hypothesized that the tail plays an active role in balancing whole-body angular momentum. To test this hypothesis, the moment of inertia (MOI) of the tail was experimentally manipulated and analyzed within the two-dimensional sagittal plane. Kangaroo rats (n=8) hopped on a treadmill at four different speeds with no tail weights, and tail weights that increased tail MOI by 10 and 20 percent, respectively. Body and tail were found to have a 90-degree phase difference while hopping in all conditions. Despite an increase of MOI at the tail, animals were still able to balance whole body angular momentum through changing the position and angular momentum of the tail. It suggests that the tail is actively utilized to balance whole body angular momentum during steady speed hopping.
Role of the Tail in Balancing Whole Body Angular Momentum in Kangaroo Rats (D. deserti)
Kangaroo rats (Dipodomys deserti) are bipedal hopping rodents that have a remarkably long tail. Studies have suggested that during bipedal hopping the tail balances angular momentum of the legs and/or body; however, the mechanism is not well understood. Video recordings of desert kangaroo rats show large tail swings during steady state hopping. From these observations, we hypothesized that the tail plays an active role in balancing whole-body angular momentum. To test this hypothesis, the moment of inertia (MOI) of the tail was experimentally manipulated and analyzed within the two-dimensional sagittal plane. Kangaroo rats (n=8) hopped on a treadmill at four different speeds with no tail weights, and tail weights that increased tail MOI by 10 and 20 percent, respectively. Body and tail were found to have a 90-degree phase difference while hopping in all conditions. Despite an increase of MOI at the tail, animals were still able to balance whole body angular momentum through changing the position and angular momentum of the tail. It suggests that the tail is actively utilized to balance whole body angular momentum during steady speed hopping.
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