PFAS dynamics in the American black bear (Ursus americanus): Physiological stages (hyperphagia, hibernation, and post-hibernation), and temporal trends from 1989 to 2015
By Qaim Mehdi, Lauren E Blackman, Alina S Timshina, Oumnia Boubad, Colleen Olfenbuttel, Marcella J Kelly, J Bernardo Mesa-Cruz, and John A Bowden
Sci Total Environ
November 8, 2025
DOI: 10.1016/j.scitotenv.2025.180876
Per- and polyfluoroalkyl substances (PFAS) have been detected in wildlife globally, yet limited research exists on their presence in terrestrial vertebrate hibernators, such as the American black bear (Ursus americanus). Our goal was to determine plasma PFAS fluctuations across physiological stages (hyperphagia, hypophagia, mid-hibernation, late-hibernation, and post-hibernation) and temporal trends in PFAS levels in black bears over a period of three decades. Plasma from individual black bears (n = 99) contained a range of perfluoroalkyl sulfonic acids (PFSAs; C) and long-chain perfluoroalkyl carboxylic acids (PFCAs; C). Total PFAS concentrations (∑₁₀PFAS) ranged from 6.55 to 113 ng/g plasma in all black bears combined. Linear mixed-effects models revealed significant increases in ∑PFSAs from hyperphagia to late-hibernation in female black bears, whereas ∑PFCAs remained stable or declined. Notably, both PFAS classes exhibited a marked decrease during post-hibernation arousal, highlighting the influence of distinct physiological stages on PFAS levels in plasma. ∑PFSA temporal trends between 1989 and 2015 peaked around year 2002 and steadily decreased, likely due to regulatory phase-outs of C-based compounds. In contrast, several long-chain PFCAs showed increasing trends, suggesting continued environmental inputs potentially linked to ongoing production or degradation of PFCA precursors.
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