  Predator-prey coevolution is commonly thought to result in reciprocal arms
races that produce increasingly extreme and complex traits. However, such
directional change is not inevitable. Here, we provide evidence for a
previously undemonstrated dynamic that we call "strategy chases," wherein
populations explore strategies with similar levels of complexity, but differing
behaviorally. Indeed, in populations of evolving digital organisms, as prey
evolved more effective predator-avoidance strategies, they explored a wider
range of behavioral strategies in addition to exhibiting increased levels of
behavioral complexity. Furthermore, coevolved prey became more adept in
foraging, evidently through coopting components of explored sense-and-flee
avoidance strategies into sense-and-retrieve foraging strategies. Specifically,
we demonstrate that coevolution induced non-escalating exploration of
behavioral space, corresponding with significant evolutionary advancements,
including increasingly intelligent behavioral strategies.
