A resource selection model for analyzing pseudoreplicated data due to grouping behavior of animals |
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Authors: | Hiroshi Okamura Masashi Kiyota Toshihide Kitakado |
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Institution: | 1.National Research Institute of Far Seas Fisheries,Kanagawa,Japan;2.Tokyo University of Marine Science and Technology,Tokyo,Japan |
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Abstract: | Quantifying resource selection is of primary interest in animal ecology. Many analyses of resource selection assume spatial
and temporal independence of the sampling unit. Autocorrelation between observations, which is a general property of ecological
variables, causes difficulties for most standard statistical procedures of resource selection because autocorrelated data
violate the assumption of independence. To overcome this problem, we develop a mixed-effects model to estimate resource selection
functions from data that are autocorrelated because of unobserved grouping behavior by animals. In the application of the
expectation-maximization (EM) algorithm, the computation of the conditional expectation of the complete-data log-likelihood
function does not have a closed-form solution requiring numerical integration. A Monte Carlo EM algorithm with Gibbs sampling
can be used effectively in such situations to find exact maximum likelihood estimates. We propose a simple automated Monte
Carlo EM algorithm with multiple sequences in which the Monte Carlo sample size is increased when the EM step is swamped by
Monte Carlo errors.We demonstrate that the model can detect inherent autocorrelation and provide reasonable variance estimates
when applied to nocturnal bird migration data. This approach could also be applied to ecological processes with various types
of spatially and temporally autocorrelated data, circumventing serious problems caused by dangerous pseudoreplication. |
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