Effect of cold exposure on water requirements on three species of small mammals.

Water turnover rate (WTR) was determined from tritiated water (3H2O) loss in the short-tailed shrew (Blarina brevicauda), red-backed vole (Clethrionomys gapperi), and white-footed mouse (Peromyscus leucopus). When given ad libitum water at Ta of 20 degrees, B. brevicauda, C. gapperi, and P. leucopus turned over 16.2, 13.8, and 6.2 ml/day, respectively; minimum WTR was 9.9, 7.8, and 3.5 ml/day, respectively. When they were given ad libitum water at 5 degrees C, WTR was 1.4 to 1.6 times higher than at 20 degrees C. On minimum water rations, WTR at 5 degrees C was 1.7 to 1.9 times higher than at 20 degrees C. Since increases in VO2 at 5 degrees C and at 20 degrees C were of about the same magnitude, increased metabolic rates may have caused increased water requirements. Total body water (TBW) was calculated from 3H2O dilution. On minimum water rations, the three species at both Ta's showed decreases in TBW and body weight, but percent body H2O increased.