Changes between Version 1 and Version 2 of EwEugModellingSwitchingBehaviourInEcosim
- Timestamp:
- 2010-01-30 19:59:05 (14 years ago)
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EwEugModellingSwitchingBehaviourInEcosim
v1 v2 7 7 1. Apparent switching away from prey that are declining in abundance, due to those prey seeing less intraspecific competition and hence spending less time at risk to predation; this effect occurs for any prey species (and impacts feeding on it by all of its predators) whenever Ecosim Feeding time adjustment is set >0 in the [[Group info.htm#_Read_time_series|Group info]] interface. 8 8 9 1. Apparent switching in Ecospace, caused by fitness-sensitive movement; when Ecospace parameters are set to cause increased (and/or directional) movement from cells where ‘fitness’ (per capita food intake minus instantaneous mortality rate) is lower, predators will appear (for the system as a whole) to switch to more abundant prey, and prey that are declining in abundance will see lower predation rates in the cells where they remain concentrated.9 2. Apparent switching in Ecospace, caused by fitness-sensitive movement; when Ecospace parameters are set to cause increased (and/or directional) movement from cells where ‘fitness’ (per capita food intake minus instantaneous mortality rate) is lower, predators will appear (for the system as a whole) to switch to more abundant prey, and prey that are declining in abundance will see lower predation rates in the cells where they remain concentrated. 10 10 11 1. Explicit changes in Ecosim rates of effective search, representing fine-scale 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 3. Explicit changes in Ecosim rates of effective search, representing fine-scale 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. 12 12 13 13 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 prey-specific foraging arenas. The equation used for this modification is aij(t) = KijaijBi(t)Pj / Σi’ai’jBi ’(t)Pj Eq. 55 … … 27 27 Without switching 28 28 29 ../Resources/Images/03000033.png ../Resources/Images/03000034.png ../Resources/Images/03000035.png 29 [[Image(wiki:EwEugImages:03000033.png)]] [[Image(wiki:EwEugImages:03000034.png)]] [[Image(wiki:EwEugImages:03000035.png)]] 30 30 31 31 With switching (power parameter = 2) 32 32 33 ../Resources/Images/03000036.png ../Resources/Images/03000037.png ../Resources/Images/03000038.png 33 [[Image(wiki:EwEugImages:03000036.png)]] [[Image(wiki:EwEugImages:03000037.png)]] [[Image(wiki:EwEugImages:03000038.png)]] 34 34 35 35 Figure 3.11. Effect of allowing switching for migratory striped bass (Chesapeake Bay model, Christensen et al., MS).
