Prey animals balance their access to food, shelter, or mates with their need to avoid being consumed by predators. However, not all predators in the environment pose equal threats. Prey would miss many resource acquisition opportunities if they responded to all predators the same way. Thus, prey use risk assessment to decide which predators should be avoided or when the threat is low enough to pursue resources. Factors like the predator to prey size ratio as well as the components of the predator’s diet could influence the prey’s risk assessment decisions. Rusty crayfish were exposed to odor cues from Largemouth Bass which were fed diets consisting of conspecifics, two species of heterospecific crayfish, and fish food pellets. Within the dietary treatments, crayfish were classified as vulnerable if they fell below the gape limitations of the bass, or invulnerable if they exceeded the gape limitations of the bass. This experiment was conducted in a system of flow through artificial streams using natural river water. We examined the macrophyte consumption, foraging behavior, shelter use, and movements of crayfish under various threat conditions using a multiple factor analysis.
Results/Conclusions
The MFA revealed two axes along which predator to prey size ratio and predator dietary information influence crayfish behavior. The first axis demonstrates shifts in resource use (foraging behavior and shelter use) by crayfish when the predators were large or small relative to the size of the prey. The second axis showed changes in movement frequency amongst crayfish exposed to predators fed different diets. These results indicate that crayfish can extract information about the predator’s diet and relative size from odor cues. The crayfish then incorporate this information into their risk assessment strategy to alter their behavior and make resource use decisions. Crayfish are important to the ecology of many freshwater communities because they heavily influence macrophyte and macroinvertebrate abundance, alter the habitat by constructing burrows, and serve as food resource for fishes. Changes in crayfish behavior and resource use under threat have the potential to cascade to lower trophic levels and influence community structure. Beyond crayfish, this research suggests that risk assessments by prey extend beyond predator detection and can incorporate different kinds of information contained in predator odor cues to better inform resource use decisions.