Big fish swim substantially faster than small fish, while big birds fly faster than small ones. However, the speeds of runners vary a lot less with body size, although big ones do go somewhat faster, never mind a lot of highly unreliable top speed data. Some general scaling rules might help. Assume that the cost of transport (cost per distance) varies with body mass^0.68, that the maximum metabolic rate varies with body mass^0.81, and that efficiencies and so forth don't vary with body size. How many times faster should a 450 kilogram bear be able to run than the top speed of a 45gram rodent