Estimate N, the size of a closed population, by several conventional non-spatial capture--recapture methods.
closedN(object, estimator = NULL, level = 0.95, maxN = 1e+07,
dmax = 10 )capthist object If your data are from spatial sampling (e.g. grid trapping) it is
recommended that you do not use these methods to estimate
population size (see Efford and Fewster 2013). Instead, fit a spatial model
and estimate population size with region.N.
Data are provided as spatial capture histories, but the spatial information (trapping locations) is ignored.
AIC-based model selection is available for the maximum-likelihood
estimators null, zippin, darroch, h2, and
betabinomial.
Model weights are calculated as $$w_i = \frac{\exp(-\Delta_i / 2)}{ \sum{\exp(-\Delta_i / 2)}}$$
Models for which dAICc > dmax are given a weight of zero and are
excluded from the summation, as are non-likelihood models.
Computation of null, zippin and darroch estimates
differs slightly from Otis et al. (1978) in that the likelihood is
maximized over real values of N between Mt1 and maxN,
whereas Otis et al. considered only integer values.
Asymmetric confidence intervals are obtained in the same way for all estimators, using a log transformation of \(\hat{N}-Mt1\) following Burnham et al. (1987), Chao (1987) and Rexstad and Burnham (1991).
The available estimators are
| Name | Model | Description | Reference |
null |
M0 | null | Otis et al. 1978 p.105 |
zippin |
Mb | removal | Otis et al. 1978 p.108 |
darroch |
Mt | Darroch | Otis et al. 1978 p.106-7 |
h2 |
Mh | 2-part finite mixture | Pledger 2000 |
betabinomial |
Mh | Beta-binomial continuous mixture | Dorazio and Royle 2003 |
jackknife |
Mh | jackknife | Burnham and Overton 1978 |
chao |
Mh | Chao's Mh estimator | Chao 1987 |
chaomod |
Mh | Chao's modified Mh estimator | Chao 1987 |
chao.th1 |
Mth | sample coverage estimator 1 | Lee and Chao 1994 |
chao.th2 |
Mth | sample coverage estimator 2 | Lee and Chao 1994 |
Burnham, K. P. and Overton, W. S. (1978) Estimating the size of a closed population when capture probabilities vary among animals. Biometrika 65, 625--633.
Chao, A. (1987) Estimating the population size for capture--recapture data with unequal catchability. Biometrics 43, 783--791.
Chao, A. and Shen, T.-J. (2010) Program SPADE (Species Prediction And Diversity Estimation). Program and User's Guide available online at http://chao.stat.nthu.edu.tw.
Dorazio, R. M. and Royle, J. A. (2003) Mixture models for estimating the size of a closed population when capture rates vary among individuals. Biometrics 59, 351--364.
Efford, M. G. and Fewster, R. M. (2013) Estimating population size by spatially explicit capture--recapture. Oikos 122, 918--928.
Hurvich, C. M. and Tsai, C. L. (1989) Regression and time series model selection in small samples. Biometrika 76, 297--307.
Lee, S.-M. and Chao, A. (1994) Estimating population size via sample coverage for closed capture-recapture models. Biometrics 50, 88--97.
Otis, D. L., Burnham, K. P., White, G. C. and Anderson, D. R. (1978) Statistical inference from capture data on closed animal populations. Wildlife Monographs 62, 1--135.
Pledger, S. (2000) Unified maximum likelihood estimates for closed capture-recapture models using mixtures. Biometrics 56, 434--442.
Rexstad, E. and Burnham, K. (1991) User's guide for interactive program CAPTURE. Colorado Cooperative Fish and Wildlife Research Unit, Fort Collins, Colorado, USA.