Integrated population modeling provides the first empirical estimates of vital rates and abundance for polar bears in the Chukchi Sea

Eric V. Regehr; Nathan J. Hostetter; Ryan H. Wilson; Karyn D. Rode; Michelle St. Martin; Sarah J. Converse

doi:10.1038/s41598-018-34824-7

Integrated population modeling provides the first empirical estimates of vital rates and abundance for polar bears in the Chukchi Sea

Scientific Reports

By: Eric V. Regehr, Nathan J. Hostetter, Ryan H. Wilson, Karyn D. Rode, Michelle St. Martin, and Sarah J. Converse

https://doi.org/10.1038/s41598-018-34824-7

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Abstract

Large carnivores are imperiled globally, and characteristics making them vulnerable to extinction (e.g., low densities and expansive ranges) also make it difficult to estimate demographic parameters needed for management. Here we develop an integrated population model to analyze capture-recapture, radiotelemetry, and count data for the Chukchi Sea subpopulation of polar bears (Ursus maritimus), 2008–2016. Our model addressed several challenges in capture-recapture studies for polar bears by including a multievent structure reflecting location and life history states, while accommodating state uncertainty. Female breeding probability was 0.83 (95% credible interval [CRI] = 0.71–0.90), with litter sizes of 2.18 (95% CRI = 1.71–2.82) for age-zero and 1.61 (95% CRI = 1.46–1.80) for age-one cubs. Total adult survival was 0.90 (95% CRI = 0.86–0.92) for females and 0.89 (95% CRI = 0.83–0.93) for males. Spring on-ice densities west of Alaska were 0.0030 bears/km² (95% CRI = 0.0016–0.0060), similar to 1980s-era density estimates although methodological differences complicate comparison. Abundance of the Chukchi Sea subpopulation, derived by extrapolating density from the study area using a spatially-explicit habitat metric, was 2,937 bears (95% CRI = 1,552–5,944). Our findings are consistent with other lines of evidence suggesting the Chukchi Sea subpopulation has been productive in recent years, although it is uncertain how long this will continue given sea-ice loss due to climate change.

Additional publication details
Publication type	Article
Publication Subtype	Journal Article
Title	Integrated population modeling provides the first empirical estimates of vital rates and abundance for polar bears in the Chukchi Sea
Series title	Scientific Reports
DOI	10.1038/s41598-018-34824-7
Volume	8
Year Published	2018
Language	English
Publisher	Scientific Reports
Contributing office(s)	Coop Res Unit Seattle
Description	16780, 12 p.
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