Measuring the lipid content of live animals using cyclopropane gas.

The cyclopropane technique was validated, and it accurately estimated the lipid mass of six pond turtles (Trachemys scripta). This technique provided more accurate estimates of lipid mass and lipid-free mass (by difference) than other nonfatal techniques. This technique was accurate despite the turtles' low lipid contents (0.71-3.5% of body mass), variable water contents (65-74% of body mass), and variable body temperatures (approximately 23-31 degrees C). A computer model of the cyclopropane technique revealed that an analytical error of 1% in variables measured (e.g., body water content and body temperature) may cause errors of less than 1-6% in lipid estimates.