Determining the fitness consequences of antipredation behavior

Any animal whose form or behavior facilitates the avoidanceof predators or escape when attacked by predators will havea greater probability of surviving to breed and therefore greaterprobability of producing offspring (i.e., fitness). Althoughin theory the fitness consequences of any antipredation behaviorcan simply be measured by the resultant probability of survivalor death, determining the functional significance of antipredationbehavior presents a surprising problem. In this review we drawattention to the problem that fitness consequences of antipredationbehaviors cannot be determined without considering the potentialfor reduction of predation risk, or increased reproductive output,through other compensatory behaviors than the behaviors understudy. We believe we have reached the limits of what we canever understand about the ecological effects of antipredationbehavior from empirical studies that simply correlate a singlebehavior with an apparent fitness consequence. Future empiricalstudies must involve many behaviors to consider the range ofpotential compensation to predation risk. This is because antipredationbehaviors are a composite of many behaviors that an animal canadjust to accomplish its ends. We show that observed variationin antipredation behavior does not have to reflect fitness andwe demonstrate that few studies can draw unambiguous conclusionsabout the fitness consequences of antipredation behavior. Lastly,we provide suggestions of how future research should best betargeted so that, even in the absence of death rates or changesin reproductive output, reasonable inferences of the fitnessconsequences of antipredation behaviors can be made.