The ecophysiological significance of calcium bicarbonate in the urine of subterranean rodents: Testing a hypothesis

1. 1. A comparative study of calcium and bicarbonate in the urine was carried out on the subterranean mole rat Cryptomys hottenlotus and the terrestrial vlei rat Otomys irroratus. 2. 2. The two species were kept on two different diets; carrots, a high calcium diet (41 mg/100kg) or potatoes, a low calcium diet (14mg/100g). 3. 3. The results show that the urine of the mole rat contained high values of calcium bicarbonate on either diet. 4. 4. The urine of the vlei rat showed high values of calcium bicarbonate only when kept on the high calcium diet. 5. 5. From these results we assume that in subterranean rodents excretion of calcium bicarbonate is an adaptive mechanism to unload CO2 without increasing its concentration in the hypercapnic environment. © 1985.