Masters Thesis

An intraspecific comparison of positive and negative water balance in Dipodomys heermanni tularensis.

It has been reported by Chew (1965) that all pathways of water exchange are reduced when mammals are subjected to dehydration. With few exceptions, evaporation is the major loss, and usually the greatest absolute conservation of water is realized by the reduction of urine and fecal water loss (Chew, 1965). Research dealing with the water economy of kangaroo rats (Dipodomys) has primarily centered on Eb_ merriami. This species is the most polytypic and widely distributed species of the genus and characteristically occupies extreme desert habitats (Carpenter, 1966). Extensive studies by Schmidt-Nielsen and Schmidt-Nielsen (1951) and summarized by Schmidt-Nielsen (1964) have reported EU_ merriami's structural, physiological, and behavioral adaptations to the conservation of water. Using the extensive studies by the Schmidt-Nielsens as a basis of comparison, other researchers have studied the extent to which the availa- bility of water in different habitats acts as a factor in selection. It is to be expected that the water require- ments and exchanges of each species of mammal have evolved into a "fit" with its environment which precludes its expanding its range into environments that are more rigorous (Chew, 1965).

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