ADRIAN HAILEY*

(Received 27 October 1983)

SUMMARY

The mean body temperature (T_b) of active male Ophisaurus apodus in a thermal gradient was 27.7^oC (range 24-35^oC). Standard metabolic rate (SMR) between 11 and 35^oC had an overall Q₁₀ of 3.0 (95% confidence limits 2.7 to 3.3) and was 2/3 that expected of a 330g lizard. The SMR of O. apodus was lower and more temperature sensitive than that of English Anguis fragilis, after compensation for the size difference. This would be advantageous if high latitude is correlated with a lower mean and a greater range of activity T_bs. Such a pattern was found in published records of lacertid T_bs, but not of anguid T_bs. Anguid T_bs are significantly lower and more variable than those of lacertids. Metabolic rate at 11^oC was not altered during hibernation.

O. apodus did not ventilate during induced maximal activity, which was an intense burst of about 15s, and up to 3 min of less intense twisting. Maximal oxygen exchange capacity was about 0.4 ml g^-1 h^-1 at 35^oC, similar to that of large skinks. This reflects the cruising forager lifestyle. Anaerobic capacity was 0.55 mg lactate g^-1 at 25^oC, lower than that of other lizards. This reflects the reliance of O. apodus on mineral defence, its osteoderms accounting for 9.1% of live weight; O. apodus is 70% as armoured as a similarly sized Testudo. The genus Ophisaurus includes a range of lifestyles, defensive methods and exercise physiology.

* Present address: Ecology/computing unit, SCE, Rutherford College, University of Kent, Canterbury CT2 7NX.