Changes between Version 3 and Version 4 of EwEugForagingTimeAndPredationRisk


Ignore:
Timestamp:
2010-01-28 16:17:03 (9 years ago)
Author:
varunr
Comment:

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  • EwEugForagingTimeAndPredationRisk

    v3 v4  
    33The food consumption prediction relationship in Eq. 52 (see [[Predicting consumption.htm|Predicting consumption]]) contains two parameters that directly influence the time spent feeding and the predation risk that feeding may entail: ''a'',,''ij'',, and ''v’'',,''ij'',,. To model possible linked changes in these parameters with changes in food availability as measured by per biomass food intake rate ''c'',,''it'',,'' = Q'',,''it'',,'' / B''^''it''^ (''i''=juvenile index ''J'' or adult index ''A''), we need to specify how changes in ''c'',,''it'',, will influence at least relative time spent foraging. 
    44 
    5 Denoting the relative time spent foraging as ''T'',,''it'',,, measured such that the rate of effective search during any model time step can be predicted as ''a'',,''jit'',, = ''T'',,''it'',,'' a'',,''ji'',, for each prey type'' j'' that ''i'' eats. Further, we assume that time spent vulnerable to predation, as measured by'' v’'',,''ij'',, for all predators j on i, is inversely related to ''T''''it'', i.e., v’,,ij,,t = v’,,ij,, / T,,it,,. An alternative structure that gives similar results is to leave the ''a'',,''ij'',, constant, while varying the ''v'',,''ij'',, by setting ''v'',,''ijt'',,'' = T'',,''jt'',,'' · v'',,''ij'',,''''in the numerator of Eq. 52 in [wiki:EwEugPredictingConsumption] and ''v'',,''ijt'',,'' = T'',,''it'',,'' · v'',,''ij'',, in the denominator. 
     5Denoting the relative time spent foraging as ''T'',,''it'',,, measured such that the rate of effective search during any model time step can be predicted as ''a'',,''jit'',, = ''T'',,''it'',,'' a'',,''ji'',, for each prey type'' j'' that ''i'' eats. Further, we assume that time spent vulnerable to predation, as measured by'' v’'',,''ij'',, for all predators j on i, is inversely related to ''T''''it'', i.e., v’,,ij,,t = v’,,ij,, / T,,it,,. An alternative structure that gives similar results is to leave the ''a'',,''ij'',, constant, while varying the ''v'',,''ij'',, by setting ''v'',,''ijt'',,'' = T'',,''jt'',,'' · v'',,''ij'',,''''in the numerator of Eq. 52 in [wiki:EwEugPredictingConsumption Predicting Consumption] and ''v'',,''ijt'',,'' = T'',,''it'',,'' · v'',,''ij'',, in the denominator. 
    66 
    77For convenience in estimating the ''a'',,''ij'',, and ''v’'',,''ij'',, parameters, we scale ''T'',,''it'',, so that ''T'',,''i0'',, = 1, and ''v’,,I j,,''= ''v'',,''ij'',,. Using these scaling conventions, the key issue then becomes how to functionally relate T,,it,, to food intake rate ''c'',,''it'',, so as to represent the hypothesis that animals with lots of food available will simply spend less time foraging, rather than increase food intake rates.