Introduction

A simple biological problem may arouse our interest, but as we gain more knowledge the questions ramify and appear to grow in complexity. This may take us to new and seemingly unrelated problems, but in retrospect they are all related to the desire to find out how things work. If we are fortunate we will gain some insight, and when we understand underlying principles, the greatest reward seems to be in the simplicity of the answers.

Twenty-five years ago I had an opportunity to visit the Arizona deserts, and I was much impressed by their abundant animal life, which for me was quite unexpected. In particular, it surprised me that small rodents were quite numerous, in spite of the obvious absence of drinking water. What impressed me equally was that virtually no scientific information, other than a few anecdotal accounts, was available on how these animals could live seemingly without water. It has since become abundantly clear that the water balance of a desert rodent, such as a kangaroo rat, is quite like that of any other animal, that is, for the animal to remain in water balance, the intake of water must equal the total losses. It has become equally clear that they do not eke out a marginal existence during the long periods of drought; they manage as well as any animal that is at home in its natural environment.