Diel recordings of VO2 under a 12 h Light/12 h Dark regime, constant light or constant dark reveal a strong endogenous diurnal rhythm in L. sicula. L. vivipara show an exogeneous rhythm with activity occurring only in the light whilst L. viridis have a weak endogeneous rhythm that is modified by behavioural factors and inhibited by dark. 2. Standard (or basal) VO2 can only be attained after several hours in an 'indifferent' environment, shielded from extraneous stimuli. Measurements must be at night (light or dark) for unrestrained L. sicula and in the dark (day or night, restrained or unrestrained) for L. vivipara and L. viridis. Intrageneric std VO2 (ml h-1 STPD) = 0.328 W0.76 or 0.216 W0.77 for 1- or 3-days starvation at 30 degrees C for 0.2 to 34 g Lacerta. 3. Intrageneric maximum VO2 (determined for 30 to 60 s of provoked activity during the day) = 2.66 W0.747 at 30 degrees C for 1-days starvation. 4. Respiratory exchange ratio, R = 0.75 or 0.85 for std VO2 after 1 or 3 days starvation and 0.95 and 1.45 for mean daily and max VO2. High R values are considered a result of anaerobic metabolism and hyperventilation during activity.
