title: Minimum cost of transport in Asian elephants: do we really need a bigger elephant?
abstract: Body mass is the primary determinant of an animal's energy requirements. At their optimum walking speed, large animals have lower mass-specific energy requirements for locomotion than small ones. In animals ranging in size from 0.8 g (roach) to 260 kg (zebu steer), the minimum cost of transport (COT(min)) decreases with increasing body size roughly as COT(min)∝body mass (M(b))(-0.316±0.023) (95% CI). Typically, the variation of COT(min) with body mass is weaker at the intraspecific level as a result of physiological and geometric similarity within closely related species. The interspecific relationship estimates that an adult elephant, with twice the body mass of a mid-sized elephant, should be able to move its body approximately 23% cheaper than the smaller elephant. We sought to determine whether adult Asian and sub-adult African elephants follow a single quasi-intraspecific relationship, and extend the interspecific relationship between COT(min) and body mass to 12-fold larger animals. Physiological and possibly geometric similarity between adult Asian elephants and sub-adult African elephants caused body mass to have a no effect on COT(min) (COT(min)∝M(b)(0.007±0.455)). The COT(min) in elephants occurred at walking speeds between 1.3 and ∼1.5 m s(-1), and at Froude numbers between 0.10 and 0.24. The addition of adult Asian elephants to the interspecific relationship resulted in COT(min)∝M (-0.277±0.046)(b). The quasi-intraspecific relationship between body mass and COT(min) among elephants caused the interspecific relationship to underestimate COT(min) in larger elephants.
authors.affiliation: USDA/APHIS, 816 White Pine Drive, Bellvue, CO 80512, USA. vaughan.a.langman@aphis.usda.gov
authors.forename: Vaughan A
authors.initials: VA
authors.lastname: Langman
authors.forename: Michael F
authors.initials: MF
authors.lastname: Rowe
authors.forename: Thomas J
authors.initials: TJ
authors.lastname: Roberts
authors.forename: Nathanial V
authors.initials: NV
authors.lastname: Langman
authors.forename: Charles R
authors.initials: CR
authors.lastname: Taylor
mesh_terms: D000818:Animals; D001696:Biomechanical Phenomena; D049628:Body Size; D001835:Body Weight; D004606:Elephants / Q000502:physiology*; D004734:Energy Metabolism / Q000502:physiology; D005260:Female; D005684:Gait / Q000502:physiology*; D008124:Locomotion / Q000502:physiology*; D010101:Oxygen Consumption; D015203:Reproducibility of Results; D016138:Walking