Validating a novel capability of assessing pathways of animal water gain and loss.

Understanding variations in the routes by which wild animals gain and lose water is challenging, and common methods require longitudinal sampling, which can be prohibitive. However, a new approach uses 'O ('O of animal body water), calculated from measurements of 'O and 'O in a single sample, as a natural tracer of water flux. 'O is promising, but its relationship to organismal variables such as metabolic rate and water intake have not been validated.