FISH, F.E.; FRAPPELL, P.B.; BAUDINETTE, R.V.; MACFARLANE, P.M.: Energetics of terrestrial locomotion of the platypus: Metabolic inefficiencies due to aquatic adaptation

The platypus Ornithorhynchus anatinus displays specializations in its limb structure for swimming which could negatively impact its terrestrial locomotion. Platypuses locomoted on a treadmill at speeds from 0.19 to 1.08 m/s. Video records were used for gait analysis and the metabolism of terrestrial locomotion was studied by measurement of oxygen consumption. Platypuses used walking gaits (duty factor < 0.50) with a sprawled stance. To limit interference from the extensive webbing on the forefeet, the platypuses walked on their knuckles. Metabolic rate increased linearly over a 2.4-fold range with increasing walking speed in manner similar with terrestrial mammals, but was low due to the relatively low standard metabolism of the monotreme. The cost of transport decreased with increasing speed to a minimum of 0.71 J/N m. When compared to the cost of transport for swimming, the metabolic cost for walking was 1.89 times greater. This difference means that the platypus pays a price in terrestrial locomotion by being more aquatically adapted than other semiaquatic or terrestrial mammals.