Biology Ph.D. Dissertations

Ecological Effects of Predator Information Mediated by Prey Behavior

Date of Award

2020

Document Type

Dissertation

Degree Name

Doctor of Philosophy (Ph.D.)

Department

Biological Sciences

First Advisor

Paul Moore (Advisor)

Second Advisor

Robert Green (Other)

Third Advisor

Shannon Pelini (Committee Member)

Fourth Advisor

Andrew Turner (Committee Member)

Fifth Advisor

Daniel Wiegmann (Committee Member)

Abstract

The interactions between predators and their prey are complex and drive much of what we know about the dynamics of ecological communities. When prey animals are exposed to threatening stimuli from a predator, they respond by altering their morphology, physiology, or behavior to defend themselves or avoid encountering the predator. The non-consumptive effects of predators (NCEs) are costly for prey in terms of energy use and lost opportunities to access resources. Often, the antipredator behaviors of prey impact their foraging behavior which can influence other species in the community; a process known as a behaviorally mediated trophic cascade (BMTC).

In this dissertation, predator odor cues were manipulated to explore how prey use predator information to assess threats in their environment and make decisions about resource use. The three studies were based on a tri-trophic interaction involving predatory fish, crayfish as prey, and aquatic plants as the prey’s food. Predator odors were manipulated while the foraging behavior, shelter use, and activity of prey were monitored. The abundances of aquatic plants were also measured to quantify the influence of altered crayfish foraging behavior on plant communities.

The first experiment tested the influence of predator odor presence or absence on crayfish behavior. Crayfish spent more time foraging and less time in shelter in the presence of predator odor cues compared to predator absent controls. The crayfish also consumed greater quantities of two macrophyte species in the presence of threatening odors. In the second experiment, crayfish were exposed to odors from predators that were fed four different diets and varied in their size relative to the size of the crayfish. The crayfish responded to the relative size ratios between themselves and their predators, but the direction of the response was determined by the predator’s diet. The third experiment exposed individual crayfish to odors from individual predators which varied in gape size relative to the body size of the crayfish. The crayfish responded along a gradient of relative risk by foraging more and using shelter less in the face of greater threats. Crayfish that were not as threatened foraged less and spent more time in shelter.

The results obtained across all three experiments were largely consistent and indicate that crayfish can extract detailed information from predator odor cues. Further, crayfish incorporate multiple types of predator information into threat assessments as they make resource use decisions. Subtle differences in predator odor cues alter crayfish behavior which mediates the influence of predatory fish in freshwater communities.

Link to Full Text

Share

COinS