Energetic costs of activity by lizards in the field



1. The available data related to the activity energetics of lizards in the field were collated with respect to three indices of activity energetics: the ecological cost of transport (ECT) expressed as a percentage of the total energy, the proportion of total energy used in all forms of activity (%AR), and the sustained metabolic scope (SusMS), defined as the ratio of the total energy expenditure to the total resting metabolism.

2. The ECT values of lizards ranged from 3 to 36% with five of 11 species having values >20%. The percentage AR ranged from 23 to 80% for lizards during active seasons, with most species having values > 50%. The SusMS ranged from 1·1 to 5·1.

3. Values of ECT are higher for lizards than for mammals, in part because the costs of maintenance metabolism are higher in mammals.

4. The percentage AR and SusMS values of mammals are higher than those of lizards.

5. It follows from the previous two points that the proportion of the total daily energy that is expended in non-locomotory activities is disproportionately higher in mammals compared with lizards.

6. The energy expended in locomotion is a significant portion of the energy budget of lizards. This is generally true for all seasons in which there is activity.