Estimation of Population Size Using Open Capture–Recapture Models
One of the most important needs for wildlife managers is an accurate estimate of population size. Yet, for many species, includingmost marine species and large mammals, accurate and precise estimation of numbers is one of the most dif cult of all research chal-lenges.Open-populationcapture–recapture...
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| Format: | Text |
| Language: | English |
| Published: |
2001
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| Online Access: | http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.631.2186 http://www.west-inc.com/reports/big_game/McDonald and Amstrup 2001.pdf |
| Summary: | One of the most important needs for wildlife managers is an accurate estimate of population size. Yet, for many species, includingmost marine species and large mammals, accurate and precise estimation of numbers is one of the most dif cult of all research chal-lenges.Open-populationcapture–recapturemodels haveprovenuseful inmany situationsto estimate survival probabilitiesbut typically have not been used to estimate population size. We show that open-populationmodels can be used to estimate population size by develop-ing a Horvitz–Thompson-typeestimate of population size and an estimator of its variance. Our population size estimate keys on the probability of capture at each trap occasion and therefore is quite general and can be made a function of external covariatesmeasured dur-ing the study. Here we de ne the estimator and investigate its bias, variance, and variance estimator via computer simulation. Computer simulationsmake extensive use of real data taken from a study of polar bears (Ursus maritimus) in the Beaufort Sea. The population size estimator is shown to be usefulbecauseit was negligiblybiased in all situationsstudied. The variance estimator is shown to be useful in all situations, but caution is warranted in cases of extreme capture heterogeneity. |
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