*Focal observations might reveal some NCEs related to expression of
anti-predator behaviors, although would be unlikely to quantify the
costs of such behaviors.
†This method could capture the costs of some NCEs if those costs were
expressed through a reduction in developmental survival rates.
‡ Purely correlative studies examining associations between densities of
predators and prey or hosts and parasitoids are also sometimes reported.
But, without additional evidence of a causal link (and support for the
direction of causality) such studies are often open to multiple
interpretations. Thus, we omit them from the current discussion.
Fig. 1: Demonstration of a particular enemy-risk effect fitting in to
the broader framework we describe in Box 2. An enemy-risk effect is
described by both the stage, beginning with individual response and
ending with community effects, as well as by the effects on the
abundance, distribution, and characteristics of a pest population.