title: Bayes and empirical Bayes estimators of abundance and density from spatial capture-recapture data.
abstract: In capture-recapture and mark-resight surveys, movements of individuals both within and between sampling periods can alter the susceptibility of individuals to detection over the region of sampling. In these circumstances spatially explicit capture-recapture (SECR) models, which incorporate the observed locations of individuals, allow population density and abundance to be estimated while accounting for differences in detectability of individuals. In this paper I propose two Bayesian SECR models, one for the analysis of recaptures observed in trapping arrays and another for the analysis of recaptures observed in area searches. In formulating these models I used distinct submodels to specify the distribution of individual home-range centers and the observable recaptures associated with these individuals. This separation of ecological and observational processes allowed me to derive a formal connection between Bayes and empirical Bayes estimators of population abundance that has not been established previously. I showed that this connection applies to every Poisson point-process model of SECR data and provides theoretical support for a previously proposed estimator of abundance based on recaptures in trapping arrays. To illustrate results of both classical and Bayesian methods of analysis, I compared Bayes and empirical Bayes esimates of abundance and density using recaptures from simulated and real populations of animals. Real populations included two iconic datasets: recaptures of tigers detected in camera-trap surveys and recaptures of lizards detected in area-search surveys. In the datasets I analyzed, classical and Bayesian methods provided similar - and often identical - inferences, which is not surprising given the sample sizes and the noninformative priors used in the analyses.
authors.affiliation: U.S. Geological Survey, Southeast Ecological Science Center, Gainesville, Florida, United States of America.
authors.forename: Robert M
authors.initials: RM
authors.lastname: Dorazio
mesh_terms: D000818:Animals; D001499:Bayes Theorem; D003625:Data Collection; D017753:Ecosystem; D008116:Lizards; D015233:Models, Statistical; D009068:Movement; D016012:Poisson Distribution; D011156:Population Density; D062206:Spatial Analysis; D046010:Tigers