Water budgets of montane-mesic and lowland-xeric populations of yellow-bellied marmots

Abstract

1. 1. Lowland-xeric (LX) marmots required significantly less total water than montane-mesic (MM) marmots. In the laboratory the major source of water for both populations was drinking (73–74% of total water); however, since marmots have never been observed drinking in the field, vegetation must be the major water source under natural conditions. 2. 2. Water output was primarily urinary loss; urine volume was lower and urine concentration higher in LX than MM marmots. Although water content of the feces was the same for both populations, fecal water loss was greater for MM marmots. Evaporative water loss was greater in the LX population. 3. 3. Water requirements can not be met through metabolic water since the amount of water lost through evaporation and feces exceeded metabolic water production for both populations. 4. 4. Conservation of water under restricted conditions resulted largely from reduced urinary and fecal losses for both MM and LX marmots. 5. 5. Lower water requirements of the LX marmots are adaptive for animals confronted with limited water availability.