AN INDIVIDUAL-BASED MODEL FOR TRADITIONAL FORAGING BEHAVIOR: INVESTIGATING EFFECTS OF ENVIRONMENTAL FLUCTUATION

Authors


*Address all correspondence to A. R. Kanarek, Department of Biology, Colorado State University, Box 1878, Fort Collins, CO 80523.

Abstract

Abstract We present an individual-based model to simulate the evolution of traditional foraging strategies in a fluctuating environment. The parameters and procedures are based on observed behavior of barnacle geese, Branta leucopsis, during spring staging off the coast of Helgeland, Norway. Within a temporally and spatially heterogeneous environment, goose movement is modeled according to state-dependent site selection decisions that maximize food intake. The aim of each individual is to optimize fitness (survival and reproduction) by gaining enough food (energy reserves) during 3 weeks of foraging to meet a threshold of energy necessary for successful reproduction. The geese return to the same islands each year and on a daily basis choose unoccupied sites according to their rank in the population-structured dominance hierarchy, memories of previously visited sites (tradition), past reproductive success, inherited genetic influence towards site faithfulness and/or site quality, and knowledge of the available biomass density. It is assumed that with each subsequent return to a specific location, increased familiarity of the area will benefit an individual through greater food acquisition by more efficient foraging practices. In the event of variable environmental conditions, geese are faced with a critical decision to return to previously visited sites or abandon tradition to explore for something better. It is shown that habitat quality plays an integral role in population dynamics. Beyond the scope of this paper, the evolution of foraging strategies that directly affect reproductive potential is shown to inevitably determine the resilience of the population over time (Kanarek [2006]). Further experiments are required for detailed results and analysis of specific circumstances that provoke the adaptation of certain behaviors. In general, this modeling approach has the potential to reveal significant insight into the emergence of stable responses to environmental disturbance.

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