The influence of body temperature on sprint speed and anti-predatory defensive responses of the North African monitor lizard, Varanus griseus

Abstract

The running speed of the North African monitor lizard, Varanus griseus is directly proportional to its body temperature of between 21 and 37°C. Above 37°C, sprint speed does not increase. However, below 21°C, the lizards are extremely sluggish. If pursued at this lowered body temperature the animal finds it difficult to escape and so stays behind and tries to fight the predator. The degree of aggressiveness increases as body temperature is further reduced. This monitor lives in the savanna regions of northern Nigeria where the vegetation is low and hiding places are rare. The lizard might have evolved this antipredatory mechanism at low body temperatures as its last resort to survive since there is no place to take refuge in a bare area when the predator emerges.

Temperature dependence of predation depends on the relative performance of predators and prey

“…Both cruising speeds (U P and U N ) and maximum movement speeds (V P and V N ) can have hump-shaped temperature responses when plotted over large temperature ranges [25,26]. When this is the case the performance curves of predators and prey can intersect at several temperatures (see the electronic supplementary material, appendix S1).…”