Water balance and protein intake in the Mongolian gerbil (Meriones unguiculatus).

During water deprivation the gerbil increasingly reduced its intake of protein as the protein content of the diet increased thus minimising water stress. When given a choice of diet, increased preference was shown for that with the lower protein content. Despite the reduction in intake, the gerbils became dehydrated, the extent being least on the low protein diet. Gerbils remained in water balance on a high protein diet with 2% saline to drink. The predicted maximum urine osmolality, from renal structural indices, was less than the actual measured value, possibly reflecting the well-developed pelvic anatomy.