getDiet: Get diet of predator at size, resolved by prey species

Description

Calculates the rate at which a predator of a particular species and size consumes biomass of each prey species, resource, and other components of the ecosystem. Returns either the rates in grams/year or the proportion of the total consumption rate.

Usage

getDiet(
  params,
  n = initialN(params),
  n_pp = initialNResource(params),
  n_other = initialNOther(params),
  proportion = TRUE
)

Value

An array (predator species x predator size x (prey species + resource + other components). Dimnames are "prey", "w", and "predator".

Arguments

params: A MizerParams object
n: A matrix of species abundances (species x size).
n_pp: A vector of the resource abundance by size
n_other: A list of abundances for other dynamical components of the ecosystem
proportion: If TRUE (default) the function returns the diet as a proportion of the total consumption rate. If FALSE it returns the consumption rate in grams per year.

Details

The rates $D_{ij}(w)$ at which a predator of species $i$ and size $w$ consumes biomass from prey species $j$ are calculated from the predation kernel $\phi_i(w, w_p)$, the search volume $\gamma_i(w)$, the feeding level $f_i(w)$, the species interaction matrix $\theta_{ij}$ and the prey abundance density $N_j(w_p)$: $$ D_{ij}(w, w_p) = (1-f_i(w)) \gamma_i(w) \theta_{ij} \int N_j(w_p) \phi_i(w, w_p) w_p dw_p. $$ The prey index $j$ runs over all species and the resource.

Extra columns are added for the external encounter rate and for any extra ecosystem components in your model for which you have defined an encounter rate function. These encounter rates are multiplied by $1-f_i(w)$ to give the rate of consumption of biomass from these extra components.

This function performs the same integration as getEncounter() but does not aggregate over prey species, and multiplies by $1-f_i(w)$ to get the consumed biomass rather than the available biomass. Outside the range of sizes for a predator species the returned rate is zero.

Examples

Run this code

diet <- getDiet(NS_params)
str(diet)