| Summary: | Long-finned pilot whales (Globicephala melas) are a large delphinid species and are found in cold temperate regions worldwide. They are the most stranded cetaceans in the world; however, the predominant drivers of these events are poorly understood. Studies on smaller stranded dolphins have shown that animals in worse physical condition had elevated blubber cortisol levels. Thus, levels of cortisol may indicate the animal’s health prior to stranding. In this study the levels of blubber cortisol from pilot whales stranded in the north of Iceland were quantified and compared to POP levels and physical factors. The average cortisol concentration was lower on average in adult males than adult females and were comparable to those of similarly sized stranded dolphins, which had a six-fold increase compared to non-stranded whales. Indications of sex differences may be a result of recent birthing, causing females to experience elevated stress. From a pooled sample, certain POPs, and fat percentage correlated positively with cortisol levels in the top layer but not the other layers. That may be explained by the top layer representing circulatory concentrations further back in time. A larger and more diverse sample set is needed to confirm that. The accumulation of POPs was greater on average in immature individuals than adults, while among adults, males had a higher concentration than females. Interestingly, POP levels showed a decreasing trend when compared to historic levels, with most levels below the suggested harmful threshold proposed in the literature.
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