Retrospective analysis of the lifetime endocrine response of southern right whale calves to gull wounding and harassment: A baleen hormone approach

Patterns of cortisol and corticosterone concentrations in humpback whale (Megaptera novaeangliae) baleen are associated with different causes of death

“…During this period of baleen growth (2012–2016), the North Pacific marine ecosystem experienced a severe heatwave from 2014 to 2016 that resulted in increased sea surface temperatures (anomalies greater than +3°C; Cavole et al, 2016 , Di Lorenzo and Mantua, 2016 ) and weakened coastal upwellings that could have contributed to this whale’s nutritional stress. A similar rise-then-fall pattern in GCs has been documented in baleen of southern right whale ( Eubalaena australis ) calves with chronic wounding from kelp gulls ( Fernández Ajó et al, 2018 ; Fernández Ajó et al, 2020 ). In these calves, baleen GCs gradually increased as wounding became more severe, and then abruptly decreased to baseline or lower immediately before death.…”

“…Physiological state is most commonly assessed via blood sampling, but that requires animals to be handled (in captivity or by trapping), neither of which are feasible for baleen whales. Non-traditional sample media have instead been used to inform physiological state, including earplugs ( Trumble et al , 2013 ; Trumble et al, 2018 ) or baleen ( Hunt et al , 2017a ; Hunt et al , 2017b ; Fernández Ajó et al, 2018 , Hunt et al, 2018 ; Fernández et al, 2020 ) from dead whales. In live whales, measures of stress response have been obtained from feces ( Hunt et al, 2006, 2019 ; Pérez et al, 2011 ; Hunt et al , 2014a ; Corkeron et al , 2017 ; Rolland et al, 2017 ; Valenzuela-Molina et al , 2018 ), respiratory vapour ( Burgess et al , 2018 ; Mingramm et al , 2019 ) or blubber ( Pallin et al , 2018 ; Teerlink et al , 2018 ; Mingramm et al , 2020 ).…”

“…Baleen is an especially promising sample type for long-term stress and reproductive analysis because hormones are incorporated into the keratinous baleen plate as it grows ( Hunt et al, 2016 , 2017b , 2018 ; Fernández et al, 2018, 2020 ). Since baleen grows slowly and continuously over many years, a single baleen plate can hold a retrospective longitudinal record at approximately a monthly or bimonthly resolution, depending on sampling distance, of the concentrations of GCs in the whale over the baleen growth record.…”

Patterns of blubber fat deposition and evaluation of body condition in growing southern right whale calves (Eubalaena australis)

“…Our results are also consistent with a recent study that found no differences in the fatty acid profiles of living and dead calves in Península Valdés, which indicates no evidence of inefficient transfer of fatty acids from mothers to calves or variation in maternal diets. Also, another study in dead calves of this population showed stable levels of triiodothyronine (T3), a metabolic hormone that decreases under nutritional stress (Fernández Ajó et al, 2020). Notwithstanding, although we found no evidence of thinner blubber or less fat content in calves that died during high mortality years, a nutritional factor cannot be ruled out as a contributor to calf deaths in those years.…”

Potential endocrine correlation with exposure to domoic acid in Southern Right Whale (Eubalaena australis) at the Península Valdés breeding ground

“…Glucocorticoids are traditionally measured in plasma, but plasma sampling from free-ranging large whales is currently impossible. However, alternative sample types such as fecal samples, baleen, respiratory vapor, and blubber can be utilized to quantify GCs in large whales (Rolland et al 2005(Rolland et al , 2017Hunt et al 2006Hunt et al , 2014Hunt et al , 2019Hogg et al 2009;Fernández Ajó et al 2020). The analyses of fecal glucocorticoid metabolites (fGCm) have proven particularly useful for endocrine assessments of free-swimming whales, with several studies showing that fGCm correlate in meaningful ways with presumed stressors.…”