Water Relationships in the Florida Mouse

Abstract

Several aspects of water relationships were studied in the Florida mouse, Peromyscus floridanus , a species occurring in dry woodland habitats in peninsular Florida. Ad libitum food and water consumption of animals in the laboratory over three months averaged 0.09 g and 0.11 cc/g body weight/day, as compared to 0.15 g and 0.20 cc for freshly trapped animals. Field animals maintained weight on a 53% reduction of normal water intake, but weight losses occurred below this level. Some individuals appeared to stabilize body weight at reductions down to 11% of their normal water consumption. Deaths occurred at 15% of normal intake. Food consumption declined with increasing water restriction. The Florida mouse cannot survive indefinitely on dry food without water or succulent food supplements. Under conditions of total water deprivation, field animals lost an average of 27.6% of their weight before death and survived an average of 3.6 days. Corresponding values for laboratory animals were 36.6% and 6.1 days. Two mice survived on 0.35 m NaCl solution, although most animals died on 0.30 m. The lethal threshold for NaCl in this species does not appear to be modifiable by acclimation. Food consumption decreased with increasing NaCl concentration. In weight-relative normal water consumption and ability to stabilize weight at low water intake, P. floridanus agrees more with Peromyscus inhabiting arid western regions than those of more moist habitats. However, behavioral adaptations are probably of greater importance than physiological ones in permitting the Florida mouse to inhabit relatively xeric environments.