Model parameters are as follows: b and c, single and double exponents, respectively; e, the natural logarithm (2.718…); m1 and m2, scaling parameters that relate the single exponent and the double exponent, respectively, to polar bear mass; mass, polar bear mass (in kilograms); P, postural costs; and S, polar bear movement speed. In all models, postural costs are described by Equation 4 and thus depend on polar bear mass.