Osmoregulation and water balance in the springhare (Pedetes capensis).

Springhares are large rodents that live in arid and semi-arid regions of Africa. We deprived springhares of water for periods of up to 7 days to determine what physiological adaptations. If any, enable them to survive in and regions without drinking. During water deprivation, springhares lost up to 30% body weight and produced a mean maximum urine concentration of 2548 mosmol kg-1 with a maximum of 3076 mosmol kg-1 in an individual animal. Haematocrit and plasma sodium and potassium concentrations were well regulated throughout water deprivation at 47.5 +/- 3.8% and 132.6 +/- 7.4 mmol l-1 and 3.5 +/- 0.7 mmol l-1, respectively, while plasma osmolality increased slightly from 293 +/- 12.5 mosmol kg-1 to 324 +/- 7.3 mosmol kg-1. Springhares thus appeared to be good osmoregulators and were able to maintain plasma volume during 7 days of water deprivation. In addition to the production of a relatively concentrated urine, water loss was limited by the lowered solute load and faecal water loss achieved by a reduction in food consumption and by the production of very dry faeces. These abilities, together with a favourable burrow microclimate and nocturnal activity pattern, enable them to survive in arid regions.