Accounting for animal density gradients using independent information in distance sampling surveys
Autor(a) principal: | |
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Data de Publicação: | 2013 |
Outros Autores: | , , |
Tipo de documento: | Artigo |
Idioma: | eng |
Título da fonte: | Repositório Científico de Acesso Aberto de Portugal (Repositórios Cientìficos) |
Texto Completo: | http://hdl.handle.net/10400.12/2366 |
Resumo: | Distance sampling is extensively used for estimating animal density or abundance. Conventional methods assume that location of line or point transects is random with respect to the animal population, yet transects are often placed along linear features such as roads, rivers or shorelines that do not randomly sample the study region, resulting in biased estimates of abundance. If it is possible to collect additional data that allow an animal density gradient with respect to the transects to be modelled, we show how to extend the conventional distance sampling likelihood to give asymptotically unbiased estimates of density for the covered area. We illustrate the proposed methods using data for a kangaroo population surveyed by line transects laid along tracks, for which the true density is known from an independent source, and the density gradient with respect to the tracks is estimated from a sample of GPS collared animals. For this example, density of animals increases with distance from the tracks, so that detection probability is overestimated and density underestimated if the non-random location of transects is ignored. When we account for the density gradient, there is no evidence of bias in the abundance estimate. We end with a list of practical recommendations to investigators conducting distance sampling surveys where density gradients could be an issue. |
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Accounting for animal density gradients using independent information in distance sampling surveysDensity gradientsDistance samplingKangarooRoad surveysLine and point transectsWildlife abundanceDistance sampling is extensively used for estimating animal density or abundance. Conventional methods assume that location of line or point transects is random with respect to the animal population, yet transects are often placed along linear features such as roads, rivers or shorelines that do not randomly sample the study region, resulting in biased estimates of abundance. If it is possible to collect additional data that allow an animal density gradient with respect to the transects to be modelled, we show how to extend the conventional distance sampling likelihood to give asymptotically unbiased estimates of density for the covered area. We illustrate the proposed methods using data for a kangaroo population surveyed by line transects laid along tracks, for which the true density is known from an independent source, and the density gradient with respect to the tracks is estimated from a sample of GPS collared animals. For this example, density of animals increases with distance from the tracks, so that detection probability is overestimated and density underestimated if the non-random location of transects is ignored. When we account for the density gradient, there is no evidence of bias in the abundance estimate. We end with a list of practical recommendations to investigators conducting distance sampling surveys where density gradients could be an issue.Springer-VerlagRepositório do ISPAMarques, Tiago A.Buckland, Stephen T.Bispo, ReginaHowland, Brett2013-09-17T18:52:12Z2013-01-01T00:00:00Z2013-01-01T00:00:00Zinfo:eu-repo/semantics/publishedVersioninfo:eu-repo/semantics/articleapplication/pdfhttp://hdl.handle.net/10400.12/2366engStatistical Methods & Applications, 22, 67-801618-251010.1007/s10260-012-0223-2info:eu-repo/semantics/openAccessreponame:Repositório Científico de Acesso Aberto de Portugal (Repositórios Cientìficos)instname:Agência para a Sociedade do Conhecimento (UMIC) - FCT - Sociedade da Informaçãoinstacron:RCAAP2022-09-05T16:38:17Zoai:repositorio.ispa.pt:10400.12/2366Portal AgregadorONGhttps://www.rcaap.pt/oai/openaireopendoar:71602024-03-19T15:20:21.304126Repositório Científico de Acesso Aberto de Portugal (Repositórios Cientìficos) - Agência para a Sociedade do Conhecimento (UMIC) - FCT - Sociedade da Informaçãofalse |
dc.title.none.fl_str_mv |
Accounting for animal density gradients using independent information in distance sampling surveys |
title |
Accounting for animal density gradients using independent information in distance sampling surveys |
spellingShingle |
Accounting for animal density gradients using independent information in distance sampling surveys Marques, Tiago A. Density gradients Distance sampling Kangaroo Road surveys Line and point transects Wildlife abundance |
title_short |
Accounting for animal density gradients using independent information in distance sampling surveys |
title_full |
Accounting for animal density gradients using independent information in distance sampling surveys |
title_fullStr |
Accounting for animal density gradients using independent information in distance sampling surveys |
title_full_unstemmed |
Accounting for animal density gradients using independent information in distance sampling surveys |
title_sort |
Accounting for animal density gradients using independent information in distance sampling surveys |
author |
Marques, Tiago A. |
author_facet |
Marques, Tiago A. Buckland, Stephen T. Bispo, Regina Howland, Brett |
author_role |
author |
author2 |
Buckland, Stephen T. Bispo, Regina Howland, Brett |
author2_role |
author author author |
dc.contributor.none.fl_str_mv |
Repositório do ISPA |
dc.contributor.author.fl_str_mv |
Marques, Tiago A. Buckland, Stephen T. Bispo, Regina Howland, Brett |
dc.subject.por.fl_str_mv |
Density gradients Distance sampling Kangaroo Road surveys Line and point transects Wildlife abundance |
topic |
Density gradients Distance sampling Kangaroo Road surveys Line and point transects Wildlife abundance |
description |
Distance sampling is extensively used for estimating animal density or abundance. Conventional methods assume that location of line or point transects is random with respect to the animal population, yet transects are often placed along linear features such as roads, rivers or shorelines that do not randomly sample the study region, resulting in biased estimates of abundance. If it is possible to collect additional data that allow an animal density gradient with respect to the transects to be modelled, we show how to extend the conventional distance sampling likelihood to give asymptotically unbiased estimates of density for the covered area. We illustrate the proposed methods using data for a kangaroo population surveyed by line transects laid along tracks, for which the true density is known from an independent source, and the density gradient with respect to the tracks is estimated from a sample of GPS collared animals. For this example, density of animals increases with distance from the tracks, so that detection probability is overestimated and density underestimated if the non-random location of transects is ignored. When we account for the density gradient, there is no evidence of bias in the abundance estimate. We end with a list of practical recommendations to investigators conducting distance sampling surveys where density gradients could be an issue. |
publishDate |
2013 |
dc.date.none.fl_str_mv |
2013-09-17T18:52:12Z 2013-01-01T00:00:00Z 2013-01-01T00:00:00Z |
dc.type.status.fl_str_mv |
info:eu-repo/semantics/publishedVersion |
dc.type.driver.fl_str_mv |
info:eu-repo/semantics/article |
format |
article |
status_str |
publishedVersion |
dc.identifier.uri.fl_str_mv |
http://hdl.handle.net/10400.12/2366 |
url |
http://hdl.handle.net/10400.12/2366 |
dc.language.iso.fl_str_mv |
eng |
language |
eng |
dc.relation.none.fl_str_mv |
Statistical Methods & Applications, 22, 67-80 1618-2510 10.1007/s10260-012-0223-2 |
dc.rights.driver.fl_str_mv |
info:eu-repo/semantics/openAccess |
eu_rights_str_mv |
openAccess |
dc.format.none.fl_str_mv |
application/pdf |
dc.publisher.none.fl_str_mv |
Springer-Verlag |
publisher.none.fl_str_mv |
Springer-Verlag |
dc.source.none.fl_str_mv |
reponame:Repositório Científico de Acesso Aberto de Portugal (Repositórios Cientìficos) instname:Agência para a Sociedade do Conhecimento (UMIC) - FCT - Sociedade da Informação instacron:RCAAP |
instname_str |
Agência para a Sociedade do Conhecimento (UMIC) - FCT - Sociedade da Informação |
instacron_str |
RCAAP |
institution |
RCAAP |
reponame_str |
Repositório Científico de Acesso Aberto de Portugal (Repositórios Cientìficos) |
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Repositório Científico de Acesso Aberto de Portugal (Repositórios Cientìficos) |
repository.name.fl_str_mv |
Repositório Científico de Acesso Aberto de Portugal (Repositórios Cientìficos) - Agência para a Sociedade do Conhecimento (UMIC) - FCT - Sociedade da Informação |
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1799130064594403328 |