ADRIAN HAILEY* AND P. M. C. DAVIES

ABSTRACT

Absorption efficiency of viperine snakes feeding on goldfish increased slightly with temperature: the rate of digestion increased greatly. Digestion was partial at 15^oC and sometimes followed by regurgitation: at 10^oC all prey were regurgitated. Prolonged basking in N. maura in the field probably serves to increase the speed of digestion. The metabolic cost of maintaining a high body temperature (T_b) during digestion is equivalent to 4 per cent of the energy of the prey.

The level and time course of raised oxygen consumption (VO₂) following feeding on fish varied with T_b, being large and short lived (2 days) at 35^oC, small but long lasting (10 days) at 15^oC. The total energy cost of this raised VO₂ accounted for 28 per cent of the energy in the food. VO₂ during maximal activity after feeding at 35^oC was greater than that of post-absorptive snakes, indicating that the capacity for oxygen exchange does not limit the active metabolic rate of N. maura. There was no depression of oxygen consumption during hibernation.

Food consumption could not be satisfactorily estimated from the proportion of snakes (a) found handling prey or (b) with prey in the stomach. Data on metabolic costs, reproductive effort and growth are combined to give an energy budget for N. maura. The energy turnover was about a third of that predicted from studies of lizards. Snake and lizard energy budgets differ in the ratio production/assimilation; this was 0.41-0.57 in four snakes, and 0.13-0.18 in six lizards. Snakes have lower energy turnover, but allocate a greater proportion of this to reproduction and growth.