PARENT SESSION
Contributed Oral Session 116: Predator - Prey Ecology: Modeling
Thursday, August 11, 8:00 AM - 11:30 AM, Meeting Room 518 C, Level 5, Palais des congrès de Montréal

Big predators and small prey - a formula for stable dynamics?

Pachepsky, Elizaveta ^*,1, Nisbet, Roger¹, McCauley, Edward², ¹ Ecology, Evolution and Marine Biology Department, Santa Barbara, CA² Division of Ecology, Calgary, AB

ABSTRACT- We consider dynamics of predator-prey systems where predators are much larger than prey (e.g. zooplankton Daphnia and its algal prey). Like other predator-prey systems, these are commonly modeled using the Rosenzweig-MacArthur differential equation model. In this model the fact that predators are discrete individuals is ignored. Many previous studies using individual-based representations of predators (and sometimes prey) have shown this omission can be misleading. Indeed, simulation models can produce drastic differences in dynamical outcomes compared to the differential equation models. However, the cause of these differences is not well understood. We compare dynamics of a Rosenzweig-MacArthur with that of an equivalent simulation model where predators are modeled individually. We show, and explain why, in spatial context demographic stochasticity of predators can have a strong stabilizing effect on population dynamics, and why local reproduction can further stabilize the dynamics.

Key words: predator-prey, cycles, spatial dynamics, demographic stochasticity