Evol Ecol Res 2: 957-964 (2000)     Full PDF if your library subscribes.

What determines the attack distance of a stalking predator?

Shigeo Yachi*

Center for Ecological Research, Kyoto University, Otsu 520-2113, Japan

e-mail: yachi@ecology.kyoto-u.ac.jp


Stalking predation has been identified in many different taxa of animals. Although previous studies have identified environmental conditions that affect hunting success, we still lack a theory that explains diverse stalking patterns on the basis of these conditions. Here, I present an optimization model of a stalking hunt based on a predator’s multi-stage decision-making. This incorporates the essential feature of stalking predation: as the predator attacks at a shorter distance and when it attacks before the prey notices it, its hunting success is enhanced. At each step of a hunt, the predator chooses either to shorten the distance by stalking with a risk of being noticed or to attack immediately. Major conclusions are as follows: (1) The predator attains its maximum expected hunting success just by following a simple rule: keep stalking for as long as the merit of proximity exceeds the risk of losing the merit of surprise. (2) The predator attacks at a greater distance as the environmental conditions enhance the risk of losing the merit of surprise compared to the merit of proximity. (3) The optimal attack distance is neither affected by the distance where the predator starts its hunt nor by the previous stalking success as long as the merit of proximity is sufficiently large. This constancy of the optimal attack distance can be used to test if a stalking predator follows the above simple decision-making rule.

Keywords: attack distance, merit of proximity, merit of surprise, stalking predation.

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