Description:
<jats:title>ABSTRACT</jats:title><jats:p>We measured the daily energy expenditure of free‐living red foxes <jats:italic>Vulpes vulpes</jats:italic> occupying a temperate region of New South Wales, Australia. Field metabolic rate (FMR) and body water turnover were estimated using doubly labelled water. In autumn, male body mass ranged from 5 to 6.1 kg (mean 5.6 kg) and their FMRs averaged 2328 kJ/day. Female body mass in autumn ranged from 4.9 to 6.6 kg (mean 5.4 kg) and their FMRs averaged 1681 kJ/day. Body water influx for males and females was 314 and 251 mL/day, respectively. Body composition of each fox was analysed after the field measurements and revealed a significant correlation between body water content, as estimated from tritiated water space, and body lipids (<jats:italic>r</jats:italic><jats:sup>2</jats:sup> = 0.72). This supports the use of body water determination as a potentially non‐destructive method to gauge body condition.</jats:p>