Changes between Version 3 and Version 4 of EwEugModellingSwitchingBehaviourInEcosim
 Timestamp:
 20100130 20:00:38 (11 years ago)
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EwEugModellingSwitchingBehaviourInEcosim
v3 v4 10 10 3. Explicit changes in Ecosim rates of effective search, representing finescale behavioral choices by predators to spend more or less foraging time in the arenas where specific prey are concentrated. In this case, the behavioral choice among arenas is predicted from Ideal Free Distribution (IFD) arguments that predators should allocate foraging time so as to minimize time needed to obtain normal food consumption rates. 11 11 12 In the third of these approaches, the Ecosim rate of effective search aij for predator type j on prey type i is modified at each simulation time step in relation to changes in abundance of all prey types, using a ‘gravity model’ approximation for the IFD allocation of predator foraging time among preyspecific foraging arenas. The equation used for this modification is aij(t) = !KijaijBi(t)Pj / Σi’ai’jBi ’(t)Pj Eq. 5512 In the third of these approaches, the Ecosim rate of effective search aij for predator type j on prey type i is modified at each simulation time step in relation to changes in abundance of all prey types, using a ‘gravity model’ approximation for the IFD allocation of predator foraging time among preyspecific foraging arenas. The equation used for this modification is aij(t) = !KijaijBi(t)Pj / Σi’ai’jBi ’(t)Pj '''Eq. 55''' 13 13 14 14 Here, aij is the base rate of effective search calculated from Ecopath and vulnerability exchange parameters, Kij is a scaling constant that makes the timespecific aij(t) equal aij when all prey biomasses Bi are at Ecopath base values, and the ‘switching power parameter’ Pj is a usersupplied (empirical, to be estimated from field data or model fitting) power parameter representing how strongly the predator responds to changes in prey availability (switching power parameter on the Group info form). In particular: