Identifying indicators of polar bear population status

• Published in: Ecological Indicators
• Main Authors: Karyn D. Rode, Ryan R. Wilson, Justin A. Crawford, Lori T. Quakenbush
• Format: Article in Journal/Newspaper
• Language: English
• Published: Elsevier 2024
• Subjects: Arctic; Arctic Oscillation; Body condition; Mammals; Recruitment; Ringed seals; Ecology; QH540-549.5; Chukchi; Chukchi Sea; Sea ice
• Online Access: https://doi.org/10.1016/j.ecolind.2024.111638; https://doaj.org/article/bc3f3bc73efa4b9aa74fddc4ed43eacd

Monitoring trends in large mammal populations is a fundamental component of wildlife management and conservation. However, direct estimates of population size and vital rates of large mammals can be logistically challenging and expensive. Indicators that reflect trends in abundance, therefore, can be valuable tools for supporting population monitoring. Polar bears have a relatively simple life history such that a few key variables may be effective indicators for tracking changes in body condition and recruitment that affect abundance. Direct estimates of polar bear abundance are difficult to obtain due to their large home ranges in remote Arctic habitats. Changes in abundance associated with environmental conditions appear to affect polar bears largely via effects on female body condition which influence reproduction and cub survival (i.e., recruitment). Loss of sea ice habitat is further limiting researcher access for population monitoring creating a need for alternative approaches. Here we used relationships established from eight years (2008–2017) of data collected on 439 polar bears in the Chukchi Sea, to transform previously published individual-based relationships with annually available sea ice, atmospheric circulation, and prey body condition variables to predict annual mean body condition and recruitment during 2018–2022. Although annual sample sizes were limited for verifying predicted body condition and recruitment via techniques such as cross-validation, in most cases predicted annual means were closely correlated with observed means for 2008–2017. Summer sea ice and prey body condition remained within or increased relative to levels observed during 2008–2017 and predicted polar bear body condition and recruitment during 2018–2022 were largely within or above observed annual means during 2008–2017. A lack of trend in environmental and ecological variables or polar bear body condition and recruitment metrics during 2008–2022 is suggestive that the Chukchi Sea polar bear population was likely stable ...