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The Impact of Roads on the Demography of Grizzly Bears in Alberta

One of the principal factors that have reduced grizzly bear populations has been the creation of human access into grizzly bear habitat by roads built for resource extraction. Past studies have documented mortality and distributional changes of bears relative to roads but none have attempted to esti...

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Detalles Bibliográficos
Autores principales: Boulanger, John, Stenhouse, Gordon B.
Formato: Online Artículo Texto
Lenguaje:English
Publicado: Public Library of Science 2014
Materias:
Acceso en línea:https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4274100/
https://www.ncbi.nlm.nih.gov/pubmed/25532035
http://dx.doi.org/10.1371/journal.pone.0115535
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author Boulanger, John
Stenhouse, Gordon B.
author_facet Boulanger, John
Stenhouse, Gordon B.
author_sort Boulanger, John
collection PubMed
description One of the principal factors that have reduced grizzly bear populations has been the creation of human access into grizzly bear habitat by roads built for resource extraction. Past studies have documented mortality and distributional changes of bears relative to roads but none have attempted to estimate the direct demographic impact of roads in terms of both survival rates, reproductive rates, and the interaction of reproductive state of female bears with survival rate. We applied a combination of survival and reproductive models to estimate demographic parameters for threatened grizzly bear populations in Alberta. Instead of attempting to estimate mean trend we explored factors which caused biological and spatial variation in population trend. We found that sex and age class survival was related to road density with subadult bears being most vulnerable to road-based mortality. A multi-state reproduction model found that females accompanied by cubs of the year and/or yearling cubs had lower survival rates compared to females with two year olds or no cubs. A demographic model found strong spatial gradients in population trend based upon road density. Threshold road densities needed to ensure population stability were estimated to further refine targets for population recovery of grizzly bears in Alberta. Models that considered lowered survival of females with dependant offspring resulted in lower road density thresholds to ensure stable bear populations. Our results demonstrate likely spatial variation in population trend and provide an example how demographic analysis can be used to refine and direct conservation measures for threatened species.
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spelling pubmed-42741002014-12-31 The Impact of Roads on the Demography of Grizzly Bears in Alberta Boulanger, John Stenhouse, Gordon B. PLoS One Research Article One of the principal factors that have reduced grizzly bear populations has been the creation of human access into grizzly bear habitat by roads built for resource extraction. Past studies have documented mortality and distributional changes of bears relative to roads but none have attempted to estimate the direct demographic impact of roads in terms of both survival rates, reproductive rates, and the interaction of reproductive state of female bears with survival rate. We applied a combination of survival and reproductive models to estimate demographic parameters for threatened grizzly bear populations in Alberta. Instead of attempting to estimate mean trend we explored factors which caused biological and spatial variation in population trend. We found that sex and age class survival was related to road density with subadult bears being most vulnerable to road-based mortality. A multi-state reproduction model found that females accompanied by cubs of the year and/or yearling cubs had lower survival rates compared to females with two year olds or no cubs. A demographic model found strong spatial gradients in population trend based upon road density. Threshold road densities needed to ensure population stability were estimated to further refine targets for population recovery of grizzly bears in Alberta. Models that considered lowered survival of females with dependant offspring resulted in lower road density thresholds to ensure stable bear populations. Our results demonstrate likely spatial variation in population trend and provide an example how demographic analysis can be used to refine and direct conservation measures for threatened species. Public Library of Science 2014-12-22 /pmc/articles/PMC4274100/ /pubmed/25532035 http://dx.doi.org/10.1371/journal.pone.0115535 Text en © 2014 Boulanger, Stenhouse http://creativecommons.org/licenses/by/4.0/ 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 properly credited.
spellingShingle Research Article
Boulanger, John
Stenhouse, Gordon B.
The Impact of Roads on the Demography of Grizzly Bears in Alberta
title The Impact of Roads on the Demography of Grizzly Bears in Alberta
title_full The Impact of Roads on the Demography of Grizzly Bears in Alberta
title_fullStr The Impact of Roads on the Demography of Grizzly Bears in Alberta
title_full_unstemmed The Impact of Roads on the Demography of Grizzly Bears in Alberta
title_short The Impact of Roads on the Demography of Grizzly Bears in Alberta
title_sort impact of roads on the demography of grizzly bears in alberta
topic Research Article
url https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4274100/
https://www.ncbi.nlm.nih.gov/pubmed/25532035
http://dx.doi.org/10.1371/journal.pone.0115535
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