Fitting and Interpreting Occupancy Models

dc.contributor.authorWelsh, A. H.en_AU
dc.contributor.authorDonnelly, Christine F.en_AU
dc.contributor.authorLindenmayer, David Ben_AU
dc.date.accessioned2015-11-25T00:20:58Z
dc.date.available2015-11-25T00:20:58Z
dc.date.issued2013-01-10
dc.date.updated2015-12-11T07:18:35Z
dc.description.abstractWe show that occupancy models are more difficult to fit than is generally appreciated because the estimating equations often have multiple solutions, including boundary estimates which produce fitted probabilities of zero or one. The estimates are unstable when the data are sparse, making them difficult to interpret, and, even in ideal situations, highly variable. As a consequence, making accurate inference is difficult. When abundance varies over sites (which is the general rule in ecology because we expect spatial variance in abundance) and detection depends on abundance, the standard analysis suffers bias (attenuation in detection, biased estimates of occupancy and potentially finding misleading relationships between occupancy and other covariates), asymmetric sampling distributions, and slow convergence of the sampling distributions to normality. The key result of this paper is that the biases are of similar magnitude to those obtained when we ignore non-detection entirely. The fact that abundance is subject to detection error and hence is not directly observable, means that we cannot tell when bias is present (or, equivalently, how large it is) and we cannot adjust for it. This implies that we cannot tell which fit is better: the fit from the occupancy model or the fit ignoring the possibility of detection error. Therefore trying to adjust occupancy models for non-detection can be as misleading as ignoring non-detection completely. Ignoring non-detection can actually be better than trying to adjust for it.
dc.description.sponsorshipFunding was received from the Australian Research Council to support this research. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscripten_AU
dc.identifier.issn1932-6203en_AU
dc.identifier.urihttp://hdl.handle.net/1885/16721
dc.language.isoen_AUen_AU
dc.publisherPublic Library of Science
dc.rights© 2013 Welsh et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
dc.sourcePLoS ONE
dc.subjectcomputer simulation
dc.subjectecology
dc.subjectpopulation density
dc.subjectpopulation dynamics
dc.subjectreproducibility of results
dc.subjectalgorithms
dc.subjectmodels, biological
dc.subjectmodels, statistical
dc.titleFitting and Interpreting Occupancy Models
dc.typeJournal article
local.bibliographicCitation.issue1en_AU
local.bibliographicCitation.lastpage21
local.bibliographicCitation.startpagee52015en_AU
local.contributor.affiliationWelsh, Alan, College of Physical and Mathematical Sciences, CPMS Mathematical Sciences Institute, Centre for Mathematics and Its Applications, The Australian National Universityen_AU
local.contributor.affiliationLindenmayer, David, College of Medicine, Biology and Environment, CMBE Fenner School of Environment and Society, FSES General, The Australian National Universityen_AU
local.contributor.affiliationDonnelly, Christine, College of Medicine, Biology and Environment, CMBE Fenner School of Environment and Society, FSES General, The Australian National Universityen_AU
local.contributor.authoremailAlan.Welsh@anu.edu.auen_AU
local.contributor.authoruidWelsh, Alan, u8204947en_AU
local.description.notesImported from ARIESen_AU
local.identifier.absfor010401en_AU
local.identifier.absfor050104en_AU
local.identifier.absseo960501en_AU
local.identifier.ariespublicationf5625xPUB2322en_AU
local.identifier.citationvolume8en_AU
local.identifier.doi10.1371/journal.pone.0052015en_AU
local.identifier.essn1932-6203en_AU
local.identifier.scopusID2-s2.0-84872240589
local.identifier.thomsonID000313552400006
local.identifier.uidSubmittedByu3488905en_AU
local.type.statusPublished Versionen_AU

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