Prey Pursuit and Capture

For an American osprey (Pandion haliaetus) to intercept a fish in shallow water, it must perfectly time its descent and penetration of the water to match the location of its prey. Individual osprey have been observed catching many different kinds of fish, and this suggests that osprey learn to anticipate the position of their prey by observing something about individual fish (Bent, 1961). Numerous predators intercept moving prey (Curio, 1976), whether it is wolves (Canis lupus) taking down moose (Alces alces) in the Yukon or golden eagles (Aquila chrysaetos) catching rabbits (Lepus spp.) in the plains. The behavior seems to be a general one. But does it require an event timer?

For insects, the answer is probably no. At least in tiger beetles, the method of pursuit and capture is to constantly move where the prey is, with rapid halts to reorient its direction toward the location of the prey (Gilbert, 1997). An alternative strategy is that the insect measures the velocity of its prey and moves to where the prey will be. Evidence of the latter does not exist.

Do osprey pursue like tiger beetles? It is too early to tell. Computer imaging of predator and prey paths, like those done for the tiger beetle (Gilbert, 1997), is not yet used for larger animals. In the case of fish pursuit by birds, even simple video analysis is constrained by simultaneous water and air analyses. Still, this is likely to be the most informative method for determining the nature of larger predator pursuit and the mechanisms involved.

Another case where predator pursuit may involve timing is in group foraging efforts. Members of a concerted predatory effort must understand their duties in relation to other members. For example, observations of predatory groups breaking up to surround prey on scales at which they are not visible to one another requires an estimation of other group members in space and time (Curio, 1976). Similarly, knowing when to take over in the pursuit of prey in serial efforts necessitates an understanding of when to act. Knowing the traits of other individuals in the group, recognizing fatigue or opportunity, being at the right place at the right time — all of these things require clocks plus ample cognitive space for allocating memories and learned predatory skills. Interestingly, evolution has had no trouble solving similar problems under more predictable settings; honeybees appear to perform essentially the same feats of temporal economy within the hive (Moore et al., 1998).

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