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J Exp Biol. 2018 Jun 19;221(Pt 12). pii: jeb175372. doi: 10.1242/jeb.175372.

Energetic costs of locomotion in bears: is plantigrade locomotion energetically economical?

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US Geological Survey, Alaska Science Center, 4210 University Dr., Anchorage, AK 99508, USA
Department of Ecology & Evolutionary Biology, University of California, Santa Cruz, CA 95060, USA.
School of the Environment and School of Biological Sciences, Washington State University, Pullman, WA 99164, USA.
Institute for Conservation Research, San Diego Zoo Global, San Diego, CA 92027, USA.
San Diego Zoo Global, San Diego, CA 92027, USA.
Oregon Zoo, Portland, OR 97221, USA.


Ursids are the largest mammals to retain a plantigrade posture. This primitive posture has been proposed to result in reduced locomotor speed and economy relative to digitigrade and unguligrade species, particularly at high speeds. Previous energetics research on polar bears (Ursus maritimus) found locomotor costs were more than double predictions for similarly sized quadrupedal mammals, which could be a result of their plantigrade posture or due to adaptations to their Arctic marine existence. To evaluate whether polar bears are representative of terrestrial ursids or distinctly uneconomical walkers, this study measured the mass-specific metabolism, overall dynamic body acceleration, and gait kinematics of polar bears and grizzly bears (Ursus arctos) trained to rest and walk on a treadmill. At routine walking speeds, we found polar bears and grizzly bears exhibited similar costs of locomotion and gait kinematics, but differing measures of overall dynamic body acceleration. Minimum cost of transport while walking in the two species (2.21 J kg-1 m-1) was comparable to predictions for similarly sized quadrupedal mammals, but these costs doubled (4.42 J kg-1 m-1) at speeds ≥5.4 km h-1 Similar to humans, another large plantigrade mammal, bears appear to exhibit a greater economy while moving at slow speeds.


Acceleration; Cost of transport; Metabolism; Overall dynamic body acceleration; Ursus arctos; Ursus maritimus

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