Effects of vessel traffic and ocean noise on gray whale stress hormones
Leila S. Lemos, Joseph H. Haxel, Amy Olsen, Jonathan D. Burnett, Angela Smith, Todd
E. Chandler, Sharon L. Nieukirk, Shawn E. Larson, Kathleen E. Hunt, and Leigh G.Torres
Abstract: Human use of marinescapes is rapidly increasing, especially in populated nearshore
regions where recreational vessel traffic can be dense. Marine animals can have a physiological response to such elevated human activity that can impact individual health and population dynamics. To understand the physiological impacts of vessel traffic on
baleen whales, we investigated the adrenal stress response of gray whales (Eschrichtius robustus) to variable vessel traffic levels through an assessment of fecal glucocorticoid metabolite (fGC) concentrations. This analysis was conducted at the individual
level, at multiple temporal scales (1–7 days), and accounted for factors that may confound fGC: sex, age, nutritional status, and reproductive state. Data were collected in Oregon, USA, from June to October of 2016–2018. Results indicate significant correlations
between fGC, month, and vessel counts from the day prior to fecal sample collection. Furthermore, we show a significant positive correlation between vessel traffic and underwater ambient noise levels, which indicates that noise produced by vessel traffic may
be a causal factor for the increased fGC. This study increases knowledge of gray whale physiological response to vessel traffic and may inform
management decisions regarding regulations of vessel traffic activities and thresholds near critical whale habitats.