Circulating and Excreted Corticosteroids and Metabolites, Hematological, and Serum Chemistry Parameters in the Killer Whale (Orcinus orca) Before and After a Stress Response

Abstract

Comparisons of circulating and excreted corticosteroid profiles during a biological stress response could provide more data concerning the timing and magnitude of acute hormone changes in different sample matrices. A stress test was performed in 13 zoo-based killer whales (Orcinus orca) whereby animals were elevated out of the water on a rising lift-bottom platform for 20 min. Paired blood and feces were tested for cortisol, corticosterone, aldosterone, and their metabolites and hematological and serum chemistry parameters. Circulating corticosteroids significantly increased during the stress test and returned to pre-treatment concentrations within 24 h, indicating hypothalamic-pituitary-adrenal-axis activation. Concentrations of fecal corticosteroid metabolites did not change significantly during the stress test. Significant differences between pre-test levels and the stress test stage were observed for counts of white blood cells and absolute neutrophils, consistent with a stress leukogram. For serum chemistry, significant deviations from baseline levels were seen for the majority (20/37) of measured parameters. This study provides a direct measurement of the physiologic response of clinically healthy killer whales to a stress event. However, due to the lack of significant changes in fecal hormone metabolite profiles, further investigation of the excretory dynamics of corticosteroids during acute and chronic stress is warranted.

Comparisons of Serum Progesterone and Progestagen Concentrations in Normal and Abnormal Bottlenose Dolphin (Tursiops truncatus) Pregnancies

“…To evaluate if stress of capture could influence progestagens (P4 and PG) concentrations in delphinids, we analyzed serum samples (n = 14 samples) which had previously been collected during a stress test (Steinman et al, 2020) from a closely related delphinid, the killer whale (Orcinus orca), for PG and P4 concentrations as described above. For collection methods and animal descriptions see the previous publication (Steinman et al, 2020) and Supplementary Table 1.…”

Social, Reproductive and Contextual Influences on Fecal Glucocorticoid Metabolites in Captive Yangtze Finless Porpoises (Neophocaena asiaeorientalis asiaeorientalis) and Bottlenose Dolphins (Tursiops truncatus)

“…To measure the FGCM concentrations in fecal samples, we followed the method from Ayres et al [28] and Steinman et al [7], with minor modifications. Samples were thawed, and the wet feces thoroughly mixed and homogenized.…”

“…The GCM concentrations in the feces were measured using an in-house, single antibody, direct enzyme immunoassay (EIA, [54]) previously used for killer whale feces and described in Steinman et al [7]. For females, sample dilutions containing 0.0005 to 0.002 mL of fecal extracts or 0.002 mL for males were analyzed.…”

“…Such stress results in the release of multiple hormones designed to help regulate physiological allostasis, principally through increasing metabolic activity and energy availability [2][3][4]. Once the HPA system is activated, adrenocorticotropic hormone stimulates the release of glucocorticoids (GCs), and to a lesser extent in some cetaceans, including the bottlenose dolphin (BD, Tursiops truncatus) and the killer whale (Orcinus orca), the mineralocorticoid aldosterone ( [5,6] for BD; [7] for killer whale). The allostatic response, characterized by releases of GCs to an acute stimulus, is adaptive, rapid and short in duration (minutes to hours).…”

“…Although circulating GC concentrations can be an indicator of the HPA response toward a stressor, in wildlife species the actual collection process, which usually involves capture and restraint, may cause a stress response itself, thereby masking the animals' normal concentrations [37,38]. This limitation has led to the use of less invasive methods for determining an animal's allostatic state by relying on fecal GC metabolic products in multiple terrestrial species (see review of FGCM studies [39]) and a few cetacean species [6,7,34,40,41]. FGCM concentrations are influenced by pregnancy and/or parturition in BDs [41], humpback whales (Megaptera novaeangliae) [42,43] and blue whales (Balaenoptera musculus) [44].…”