Document: PAT-3-56-18

Behavioral interactions between intraguild predators: Implications for risk reduction and risk enhancement.

CRUMRINE, P.*

University of Kentucky, Lexington, KY 40506 USA ¹

Abstract:
Intraguild predation (IGP) and IGP risk/opportunity add important but understudied complexities to predator-prey interactions. Behavioral assays in addition to traditional short term predator-prey experiments that monitor prey mortality were used to evaluate several possible ways two predators, larvae of the dragonflies Anax junius and Plathemis lydia interact when sharing a common prey species, fathead minnow hatchlings (Pimephales promelas). In this system, A. junius was the top predator and P. lydia the intermediate predator and fathead minnow hatchlings were the shared prey. To quantify minnow mortality, P. promelas were exposed to A. junius only, P. lydia only, A. junius and P. lydia or neither in a 2 x 2 factorial design. An additional set of treatments in which one or both predators were unable to feed, were used to isolate behavioral changes in dragonfly larvae. Results indicate, that when these two predators preyed in combination on P. promelas, their effect was less than that predicted by the independent effects of each predator, a phenomenon known as risk reduction. The behavioral interaction between A. junius and P. lydia was asymmetric. Specifically, the presence of A. junius caused P. lydia to decrease its activity level. The presence of P. lydia elicited a diet shift in A. junius. A. junius consumed a significant number of P. lydia when they were present, but this IGP effect alone did not account for the observed level of risk reduction. This study provided insights into the conditions that result in risk reduction when prey face multiple predators.

Keywords: Anax, Plathemis, predator-prey, behavior, multiple predators

This abstract is being presented at: 9:15 AM in session:
Oral Session #55: Invertebrates in Streams: Foodwebs.