Field Experiments on Prey Selection by the Whiptail Lizard, Cnemidophorus inornatus, in Arizona

Abstract

Whiptail lizards (Cnemidophorus) forage for prey by probing their long snouts under twigs and objects on the substrate (Fitch, 1958; Milstead, 1957a), by chasing prey detected visually (Milstead 1957a; Mitchell, 1976) and by flushing prey from vegetation by climbing (Kennedy, 1968). These combinations of foraging strategies result in a great variety of prey taxa consumed (e.g., Milstead, 1957a; Fitch, 1958; Medica, 1967; Pianka, 1970; Mitchell, 1979). Many arthropods reduce the probability of predation by being aposematically colored (Wickler, 1968) and, when predators recognize these patterns, the prey may accrue survival advantage. While the ability to recognize a great range of colors had been demonstrated for lizards (Benes, 1969; Burghardt, 1977), recognition of aposematically colored insects has been studied in only a few species. In laboratory experiments, Anolis carolinensis showed a very reduced preference of polycolored (mostly aposematically colored) to unicolored insects (Sexton, 1964). Hunger level and prey type may also influence prey selection. Sexton et al. (1966) found that Anolis carolinensis fed at low levels for 15 days attacked Photinus (lightning bug) more than lizards kept at high food levels. No such differences in attack were found with Oncopeltus (milkweed bug), another aposematically colored prey. The basis of such reduced selection is not fully known, but may result from generalization from prior experience with similarly colored insect prey (Sexton, 1964) or from innate avoidance (Reznick et al. 1981), as has been demonstrated in birds (Hess, 1956; Oppenheim, 1968). In experiments with palatable and unpalatable butterflies, Ameiva ameiva was found to avoid distasteful species after only one or two trials (Boyden, 1976). Since many of the previous studies were laboratory experiments with live prey when odor and other cues were not controlled, interpretation of