Effects of Risk on Flight Initiation Distance and Escape Tactics in two Southern African Lizard Species

Escape theory predicts that flight initiation distance increases with fitness costs of not fleeing and decreases with cost of escaping. Habitat structure may affect aspects of escape such as routes and destinations. We studied escape tactics and effects of risk factors on flight initiation distance in Kalahari tree skinks Trachylepis sparsa and black girdled lizards Cordylus niger by simulating approaching predators. Probability of fleeing and flight initiation distance were greater when lizards were approached directly versus on paths bypassing them. The difference in flight initiation distance was significant in T. sparsa and marginal in C. niger. Trachylepis sparsa on trees used as refuges permitted closer approach than those on the ground. Those on ground had longer flight initiation distances when approached rapidly than slowly. Flight initiation distance in C. niger was shorter where they were habituated to human presence than where people were present infrequently. When on ground, T. sparsa escaped to trees and less frequently to logs or fallen weaver nests. When on trees, they usually escaped by running to the far side and up, and sometimes entered tree holes or weaver nests. Cordylus niger escaped by entering rock crevices. All findings verify predictions of escape theory about flight initiation distance. Differences in escape tactics suggest that each species took advantage of routes and refuges available in its habitat. Habitat structure may affect flight initiation distance when habitats differ in risk, and seems to strongly affect escape tactics