Anybody who has ever hunted goats in hilly country will know that this is nowhere near as silly as it first sounds. In the hills, goats are much more efficient than humans. The four biggest physiological problems immediately facing living organisms are respiration, fluid balance, temperature regulation and digestion. Each of these problems is intimately connected with the other three, since, at the immediate physical level, this is how life is defined. To the physiologist, life is thermodynamics in action.
Respiration involves obtaining the energy to live by oxidising food, and expelling metabolic waste.
This results in both water loss and heat gain. Metabolic heat gain can't be allowed to build up without control, so animals do things like sweating and panting, even further increasing water loss. Yet some level of heat is needed continuously by warm-blooded animals in order to do the respiration in the first place. Once again, we find ourselves back with the problem of achieving balances. Next month we will look at some of the physiological strategies employed by the animals we hunt, including the size problem.