three.samp.cir: Analytical estimate of abundance from a 3-occasion, 2-type...

In dill/wisp: Wildlife Simulation Package (wisp)

Description

Performs sex-specific harvest of animals from a simulated population, and produces analytical estimates of abundance and standard error for three-occasion change-in-ratio (CIR) estimator.

Usage

three.samp.cir(rm.pop, frac.prehunt, frac.midhunt, frac.posthunt,
               frac.harv.male.1, frac.harv.fem.1, frac.harv.male.2, frac.harv.fem.2)

Arguments

rm.pop	Population object being harvested and sampled (likely created by make.twosex.pop)
frac.prehunt	Proportion of the population sampled prior to the first harvest season
frac.midhunt	Proportion of the population sampled between the harvest seasons
frac.posthunt	Proportion of the population sampled following the second harvest season
frac.harv.male.1	Proportion of males in the population removed during first harvest
frac.harv.fem.1	Proportion of females in the population removed during first harvest
frac.harv.male.2	Proportion of males in the population removed during second harvest
frac.harv.fem.2	Proportion of females in the population removed during second harvest

Details

An extension of the two-occasion CIR technique, in which the sampling design possess two harvest periods. Assessment of the sex ratio of the population is made three times: before, between, and following the harvest seasons. Sex-specific harvest regulations are presumed to occur during each harvest season.

Value

A list is returned, consisting of

point.cir	Estimated point estimate of abundance
se.cir	Standard error of abundance estimate
coef.var	Coefficient of variation of estimate (not percentage)

Warning

It is not impossible for the point estimate of abundance to be negative; particularly when the difference in harvest between males and females is small. This is a nonsensical result, and hence, the estimate is not considered admissable. In this situation, all values returned by this function are set equal to NA.

Note

Specifically, eqn. xxx of Williams et al. (2002) is used for the point estimate, and xxx for the variance estimate.

Author(s)

Eric Rexstad, RUWPA [e-mail]

References

Borchers, Buckland, and Zucchini (2002), Estimating animal abundance: closed populations. Chapter 5 http://www.ruwpa.st-and.ac.uk/estimating.abundance

See Also

two.samp.cir, sim.cir.2, make.twosex.pop

Examples

library(wisp)
example <- make.twosex.pop(abund=200, prop.male=0.4)
example.3.result <- three.samp.cir(rm.pop=example, frac.prehunt=0.2, frac.midhunt=0.3, frac.posthunt=0.4,
                                   frac.harv.male.1=0.4, frac.harv.fem.1=0.05,
                                   frac.harv.male.2=0.5, frac.harv.fem.2=0.05)
example.3.result

dill/wisp documentation built on May 15, 2019, 8:31 a.m.