Estimating the abundance of the Southern Hudson Bay polar bear subpopulation with aerial surveys

Martyn E. Obbard, Seth Stapleton, Kevin R. Middel, Isabelle Thibault, Vincent Brodeur, Charles Jutras

Research output: Contribution to journalArticlepeer-review

9 Scopus citations

Abstract

The Southern Hudson Bay (SH) polar bear subpopulation occurs at the southern extent of the species’ range. Although capture–recapture studies indicate abundance was likely unchanged between 1986 and 2005, declines in body condition and survival occurred during the period, possibly foreshadowing a future decrease in abundance. To obtain a current estimate of abundance, we conducted a comprehensive line transect aerial survey of SH during 2011–2012. We stratified the study site by anticipated densities and flew coastal contour transects and systematically spaced inland transects in Ontario and on Akimiski Island and large offshore islands in 2011. Data were collected with double-observer and distance sampling protocols. We surveyed small islands in James Bay and eastern Hudson Bay and flew a comprehensive transect along the Québec coastline in 2012. We observed 667 bears in Ontario and on Akimiski Island and nearby islands in 2011, and we sighted 80 bears on offshore islands during 2012. Mark–recapture distance sampling and sight–resight models yielded an estimate of 860 (SE = 174) for the 2011 study area. Our estimate of abundance for the entire SH subpopulation (943; SE = 174) suggests that abundance is unlikely to have changed significantly since 1986. However, this result should be interpreted cautiously because of the methodological differences between historical studies (physical capture–recapture) and this survey. A conservative management approach is warranted given previous increases in duration of the ice-free season, which are predicted to continue in the future, and previously documented declines in body condition and vital rates.

Original languageEnglish (US)
Pages (from-to)1713-1725
Number of pages13
JournalPolar Biology
Volume38
Issue number10
DOIs
StatePublished - Oct 7 2015

Bibliographical note

Funding Information:
Funding for the 2011 survey was provided by the Species At Risk Branch and the Wildlife Research and Monitoring Section of the Ontario Ministry of Natural Resources. The 2012 survey was jointly funded by Environment Canada, World Wildlife Fund (Canada), Ministère des Ressources naturelles et de la Faune du Québec, the Government of Nunavut Department of Environment, Makivik Corporation, and the Ontario Ministry of Natural Resources. Additional support for analysis and reporting was provided by the U.S. Geological Survey, Alaska Science Center. Any use of trade names is for descriptive purposes only and does not represent endorsement by the U.S. government. We thank helicopter pilot Doug Holtby and observers Brandon Laforest, Robbie Koostachin, Matthew Gull, and Tommy Miles for assistance in the field in 2011. We thank Twin Otter pilot Greg Dibben and observers Marc Rondeau, Stephen Casselmann, and Rod Brook for assistance during the survey of James Bay islands in 2012. We thank Twin Otter pilots Red Seguin and Emily Crombez and observers Angela Coxon, William Flaherty, Billy Nowkawalk, Peter May, and Peter Kattuk for assistance during the survey of offshore islands in eastern Hudson Bay in 2012. We thank helicopter pilot Richard Perron and observers Billy Nowkawalk, Allen House, and Abraham Snowboy for assistance during the survey of the coast and near-shore islands of Québec in 2012. Comments from T. Atwood, J. Bromaghin, and 3 anonymous referees helped us to improve an earlier version of the manuscript.

Publisher Copyright:
© 2015, Springer-Verlag Berlin Heidelberg.

Keywords

  • Abundance estimation
  • Aerial survey
  • Line transect
  • Mark–recapture distance sampling
  • Polar bear
  • Southern Hudson Bay
  • Ursus maritimus

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