PARENT SESSION
Contributed Oral Session 161: Predator - Prey Ecology: Aquatic Habitat and Food Webs
Friday, August 12, 8:00 AM - 11:30 AM, Meeting Room 519 B, Level 5, Palais des congrès de Montréal

Behavioural mechanisms underlying the observed functional response of a marine benthic invertebrate.

Wong, Melisa^*,1, Barbeau, Myriam¹, Dowd, Michael², Richard, K.¹, ¹ University of New Brunswick, Fredericton, N.B., Canada² Dalhousie University, Halifax, N.S., Canada

ABSTRACT- The functional response describes the relationship between prey density and individual predator consumption rate. Functional response models are often characterized by two parameters: rate of successful search (a), and handling time per prey (Th). In this paper, we examine the predator and prey behaviours that underlie these parameters, in an effort to identify and understand the behavioural mechanisms responsible for observed functional responses. Laboratory experiments were conducted in which predators (sea stars, Asterias vulgaris) were offered various prey densities (juvenile sea scallops, Placopecten magellanicus). We quantified predation rate, foraging behaviours (the proportion of time spent searching for or handling prey), encounter rate between predators and prey, and the various outcomes of encounters. A functional response was evident. Parameters of the functional response model were estimated using non-linear regression; they were also independently calculated from behavioural data. Parameter values calculated from behavioural data indicated that handling time per prey remained constant over prey density. In contrast, rate of successful search was found to be density dependent. An inverse polynomial was used to describe the relationship between rate of successful search and prey density, resulting in a type III functional response. Rate of successful search calculated from behavioural information were consistent with those estimated from fitting functional response models, independently validating the postulated relationship between rate of successful search and prey density. Behavioural components of rate of successful search indicated that the probability of capture upon attack was the dominant mechanism underlying the observed functional response. We conclude that behavioural information is crucial for an improved understanding of the functional response.

Key words: functional response, behavioural mechanisms, rate of successful search, marine benthic invertebrates