Baleen hormones reveal the endocrine response of southern right whale, Eubalaena australis, calves to kelp gull wounding at Península Valdés, Argentina

FERNÁNDEZ AJÓ, ALEJANDRO; HUNT, KATHLEEN E.; SIRONI, MARIANO; UHART, MARCELA; ROWNTREE, VICTORIA J.; GIESE, A. CAROLINA; MARÓN, CARINA F.; DIMARTINO, MATIAS; BUCK, C. LOREN

Florida

Congreso; 24th Biennial Conference on the Biology of Marine Mammal; 2022

The Society for Marine Mammalogy

Physiological measurements provide evidence of stressors that impact the health of wildlife. Baleen accumulates hormones as it grows, allowing the use of these samples for retrospective assessment of long-term trends in a whale´s physiology. Methodological experiments were conducted to optimize sample use of baleen. Our results indicated that baleen sample masses as low as 20 mg produce reliable and repeatable hormone data. We utilized these methods to assess the endocrine response of southern right whale (SRW, Eubalaena australis) calves to kelp gull (KG, Larus dominicanus) wounding. In Península Valdés (PV), Argentina, KG are considered micro-predators of living SRW, which results in intense harassment and sizable wounds on the whales´ backs. KG harassment has been proposed to contribute to high calf mortality experienced by the SRW population off PV in 2007-2013. We quantified lifetime patterns of glucocorticoids (GCs, an index of general physiological stress) and thyroid hormone (T3, an index of metabolic stress) in baleen recovered at necropsy from 36 SRW calves (~ 1 and 4 months old) with varying severity of KG lesions. GC levels correlated positively with the degree of wounding, while T3 remained stable irrespective of the severity of KG lesions. Our results indicate that heavily wounded calves suffered high levels of physiological stress (increased GCs levels) throughout their short lifespans. However, we found no evidence of malnutrition in mildly vs. severely wounded calves. Thus, considering the negative effect that chronic elevations in GCs levels might pose to SRW calves’ growth and immune system, KG wounding and harassment may have contributed to the high calf mortality observed at the PV calving ground.