Variation in adrenal and thyroid hormones with life-history stage in juvenile northern elephant seals (Mirounga angustirostris)

Response to capture stress involves multiple corticosteroids and is associated with serum thyroid hormone concentrations in Guadalupe fur seals (Arctocephalus philippii townsendi)

“…Previous studies in pinnipeds have shown strong associations between cortisol and thyroid concentrations (Ensminger et al 2014, Champagne et al 2015, Jelincic et al 2017. Concentrations of glucocorticoids during the first sample measured after capture did not predict thyroid function (TT4 or TT3), even when controlling for time to sample.…”

“…Prolonged elevation in glucocorticoid secretion in some individuals may reduce the ability to mount a stress response to capture and alter deiodinase production, downregulating TT3, and increasing in rT3, thus reducing metabolic rate to conserve energy. Baseline cortisol has been found to be positively associated with rT3 in northern elephant seals undergoing stress due to both handling and normal life history fluctuations (Ensminger et al 2014, Champagne et al 2015, Jelincic et al 2017. In contrast to TT3, TSR was not associated with TT4 concentrations.…”

“…Our results suggest that stimulation of aldosterone release by the HPA axis may increase with the development and use of diving. Similarly, baseline cortisol and aldosterone concentrations were strongly associated in yearling elephant seals returning from diving at sea (Jelincic et al 2017) but not associated in weanlings during the postweaning fast (Ortiz et al 2003). Future studies could further explore this hypothesis by looking at the relationship between cortisol and aldosterone in other pinniped species of multiple age classes or life history stages that vary in their diving capacity.…”

“…For example, due to the separation of terrestrial reproduction from marine feeding, many pinnipeds undergo food deprivation during periods of energetically costly activities such as nursing, development, breeding or molting. These events at various ages are associated with variation in adrenal and thyroid activity that alter circulating baseline hormone concentrations (Guinet et al 2004, Mashburn and Atkinson 2004, Greig et al 2007, Ensminger et al 2014, Champagne et al 2015, Jelincic et al 2017). Thus, contextual information about changes in hormones with life-history is critical to interpreting their implications for individual and population health.…”

Managing the Effects of Noise From Ship Traffic, Seismic Surveying and Construction on Marine Mammals in Antarctica

“…Although several anatomical predictions of the frequency range of hearing have been produced for mysticetes (Houser et al, 2001;Parks et al, 2007;Tubelli et al, 2012;Cranford and Krysl, 2015), no empirically measured audiogram exists for any mysticete species globally. Data on noise-induced hearing loss or impacts of stress in Antarctic marine mammals do not exist, although a fair amount of work has been performed on the endocrine response to stress in the southern elephant seal's close relative, the northern elephant seal (e.g., Ensminger et al, 2014;Jelincic et al, 2017). While the sounds made by Antarctic marine mammals have been documented (e.g., Erbe et al, 2017a), there is no information (such as critical ratios) to assess masking of those sounds by noise, except for four studies indicating anti-masking processes in humpback, killer, and long-finned pilot whales elsewhere (see Erbe et al, 2016).…”