Interference competition and patch choice in foraging shore crabs
Smallegange, I.M. (2007). Interference competition and patch choice in foraging shore crabs. PhD Thesis. Universiteit van Amsterdam: Amsterdam. ISBN 978-90-76894-74-4. 292 pp.
Related to:
Smallegange, I.M. (2008). Interference competition and patch choice in foraging shore crabs, in: Mees, J. et al. (Ed.) VLIZ Young Scientists' Day, Brugge, Belgium, 29 February 2008: book of abstracts. VLIZ Special Publication, 40: pp. 86-89, more
Understanding the foraging decisions and the mechanisms that underlie the dispersal behaviour of foragers is of central importance in answering questions aimed at assessing the processes that determine the spatial distribution of species. The studies in this thesis aim to contribute to answering the question ‘why do predators forage wherethey forage?’.While foraging, animals regularly compete over (access to) food in direct, aggressive interactions. These interactions deprive individuals of time that was otherwise available for foraging and this reduces their feeding rate: a process that has been termed interference competition. To formulate hypotheses on the strength of interference competition in relation to the presence of competitors and prey availability, the socalled generalized functional response model is used. The generalized functional response relates the per capita feeding rate of predators to the prey and predator (=competitor) density in a certain food patch. If the generalized functional response is known, one can subsequently derive predictions on how predators distribute themselves across patches of different quality using the theory of ideal- theory forms a widely used starting point for formulating hypotheses on the spatial distribution of foraging animals. IFD theory predicts the distribution of animals that are omniscient (‘ideal’), and that experience no travelling costs (‘free’) while moving to the patch that maximises their feeding rate. In the first, and most basic IFD model, animals are assumed to be of equal competitive ability. In that case, ideal and free animals distribute themselves such that the per capita feeding rate - as defined by the generalized functional response - is equal and constant across patches. The per capita feeding rate is determined by the generalized functional response model that is used. However, various generalized functional response models have been presented in the literature, and each one results in a they forage, firstly, detailed knowledge on the foraging behaviour, i.e. the generalized functional response, of predators is required. This notion has formed the key motivation for the work conducted in this thesis.
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