Lactational Water Balance and Recycling in White-Footed Mice, Red-Backed Voles, and Gerbils

Water budgets of lactating and non-reproductive females were constructed. Water recycling through maternal ingestion of urine from their young was measured in lactating females. Total water requirements increased by > 100% for red-backed voles (Clethrionomys gapperi), white-footed mice (Peromyscus leucopus), and gerbils (Gerbillus). Evaporative water loss accounted for 74–79% of the water turn-over in mice, but only 43–44% in voles. Urinary water loss accounted for 43–49% of the water turnover in voles. Production of tissue of the young accounted for only 1–6% of the total water budget. The amount of water consumed by drinking during lactation accounted for 75–78% of the total water turnover for mice, 87–90% for voles, and 42–55% for gerbils. Recycled water contributed up to 3.2% for voles, 11.5% for mice, and 39% for gerbils. Recycling is a more important source of water for xeric than mesic species.