Hydric constraints upon foraging in a terrestrial salamander, Desmognathus ochrophaeus (Amphibia: Plethodontidae)

The time until salamanders voluntarily abandoned foraging (the "water time limit") and the amount of water lost when salamanders abandoned foraging ("dehydration deficit") were determined for terrestrial plethodontid salamanders, Desmognathus ochrophaeus, foraging at various vapor pressure gradients in the laboratory. Salamander activity was correlated with the rate of water loss and was inversely related to the water time limit. Animals at 0.35-0.86 kPa vapor pressure gradients abandoned foraging and returned to moist retreats significantly sooner than animals in water-saturated air. The early retreat of animals in dry air was related in part to high rates of water loss and in part to the modest dehydration deficit (3.8%) at which animals abandoned foraging. Locomotor performance and foraging ability were unaffected by dehydration until dehydration deficits exceeded 12%. This suggests that salamanders in unsaturated air abandoned foraging at a low dehydration deficit to conserve and replenish water reserves rather than to avoid outright incapacitation or death.