1. 1.

    Lactate concentration ([lactate]), pH, Pco2, Po2 and bicarbonate concentration ([HCO3]) were measured in the blood of salt-water crocodiles (Crocodylus porosus Schneider) exhausted during field capture.

  2. 2.

    Body temperature after capture averaged 31.1°C.

  3. 3.

    All animals underwent high levels of anaerobic metabolism and metabolic acidosis. The largest animals attained the highest blood [lactate] and lowest pH ever observed in any animal as a result of activity.

  4. 4.

    Peak levels of [lactate] increased with increasing body mass (slope=9.72 mmoll−1 logM−1; mass M in kg), indicating a greater anaerobic capacity in larger animals. Several large crocodiles had [lactate] in excess of SOmmoll−1.

  5. 5.

    Blood pH decreased with mass (slope=0.163 pH units log M−1) and reached 6.6 in the largest animals. One animal remained acidotic for several hours and had a minimal pH of 6.42.

  6. 6.

    Blood Pco2 increased significantly and [HCO3] decreased significantly with increasing body mass.

  7. 7.

    Struggling time before exhaustion was greater in larger animals, ranging from about 5min in small (<1 kg) crocodiles to over 30min in animals over 100 kg.

  8. 8.

    During recovery, mean blood [lactate] decrement after 2h was 6.0mmoll−1 and was not significantly related to mass. Proton elimination from the blood, however, was more rapid in larger animals (slope=0.0443 μmoll−1 log M−1).

  9. 9.

    The positive mass-dependence of acid-base disturbance could be related to the greater susceptibility of large crocodiles (>700kg) to postcapture mortality.

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