Animals are unable to produce their own food and must rely either on (1) attracting, ambushing or trapping it, or (2) actively ferreting it out. Sedentary techniques variously have been termed ambush or sit-and-wait strategies; more mobile ones have been called cruise searching, widely ranging searching, active foraging or simply foraging. Some species may employ either type, depending on circumstances (Muma 1966; Cloudsley-Thompson 1991). Intermediate modes of behaviour exist and the two extremes should be viewed merely as opposite ends of a spectrum of locomotory involvement in the acquisition of food. O’Brien et al. (1990) noted that a wide variety of species engaged in “saltatory search”, i.e., alternation between scanning of the immediate environment while stationary and movement to a fresh site (Fig. 16). Two behavioural characteristics determine the dynamics of saltatory search: (1) the relative time spent moving versus scanning and (2) the angle of directional change between successive bouts of movement. Both of these vary with visual scope, visibility and other environmental factors in ways that maximize the area scanned, yet minimize overlap of successive areas searched. It would appear that animals adjust their method of foraging to suit immediate conditions and that there is greater flexibility in acquisition of food than the older binary system of classification would suggest.