Resting Metabolic Rate in the Cotton Rat Sigmodon

A great deal of recent information is available concerning the adaptation of homoiotherms to their environment. However, the bulk of this information deals with animals that have developed highly specialized mechanisms to allow them to survive in extreme environmental conditions. The less noticeable differences that occur among related populations occupying different habitats have been, for the most part, unstudied. Such investigations have great potential not only in demonstrating how selective pressures in the environment act upon a species to produce an adapted phenotype but also to show how the adaptations acquired by a species may allow it to live in diverse climatic zones.