Meeting Abstract
There has been great interest in fecal glucocorticoids (fGCs) as a measure of stress in large whales, and elevated fGCs have been shown to correlate with stressors such as entanglement and ocean noise in North Atlantic right whales (Eubalaena glacialis, NARW). However, fGCs can reflect numerous different influences besides anthropogenic stressors. Additionally, some glucocorticoid assays have mild cross-reactivity with fecal metabolites of reproductive steroids, and it is unclear to what extent such cross-reactivity might influence fGC data. Fecal mineralocorticoids (fMCs, aldosterone and its fecal metabolites) may offer a complementary measure that could help identify true adrenal activation. The mineralocorticoids are also released from the mammalian adrenal gland and typically rise in parallel with GCs during a physiological stress response. To assess feasibility of fMC assays for large whales, we tested three commercial aldosterone immunoassays with pooled NARW fecal extract. All three assays demonstrated good parallelism and accuracy, indicating that aldosterone fecal metabolites are likely present in NARW feces and are readily measurable with aldosterone antibodies. We then applied the most sensitive of these assays to 324 NARW fecal samples, assessing relationships of fMCs with existing fGC data and with reproductive steroids from the same samples. As predicted, fMCs were strongly correlated with fGCs, though the aldosterone antibody had no detectable cross-reactivity to reproductive steroids and extremely low crossreactivity to glucocorticoids. fGC data therefore appear to primarily reflect adrenal activity. Addition of fMCs to a fecal endocrine panel shows potential for identification of cases of true adrenal activation, and may potentially help disentangle the various causes of fGC elevations.
