Evaluation of fecal hormones for noninvasive research on reproduction and stress in humpback whales (Megaptera novaeangliae)

Abstract

Fecal hormone analysis shows high potential for noninvasive assessment of population-level patterns in stress and reproduction of marine mammals. However, the marine environment presents unique challenges for fecal sample collection. Data are still lacking on collection methodology and assay validations for most species, particularly for those mysticete whales that have variable diets. In this study we tested collection techniques for fecal samples of free-swimming humpback whales (Megaptera novaeangliae), and validated immunoassays for five steroid and thyroid hormones. Resulting data were used for preliminary physiological validations, i.e., comparisons to independently confirmed sex and reproductive state. Pregnant females had significantly higher fecal progestins and glucocorticoids than did other demographic categories of whales. Two possible cases of previously undetected pregnancies were noted. Males had significantly higher fecal testosterone metabolites than nonpregnant females. Fecal glucocorticoids were significantly elevated in pregnant females and mature males compared to nonpregnant females. Calf fecal samples had elevated concentrations of all fecal hormones. Fecal thyroid hormones showed a significant seasonal decline from spring to summer. Though sample sizes were small, and sampling was necessarily opportunistic, these patterns indicate that noninvasive fecal hormone analysis may facilitate studies of reproduction, stress and potentially energetics in humpback whales.

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

“…However, we were able to provide a physiologic validation of our FGCM assay system by detecting significantly increased hormone concentrations during pregnancy as compared to non-pregnant females and males. This agrees with circulating GC and excreted GCM changes that have been documented during pregnancy in other cetaceans [29,41,43,60,61]. In addition, and as would be expected, we saw increased concentrations during the mid and late pregnancy stages compared to the early stage, and concentrations significantly increased during the final months prior to parturition (Table 3, Figure 1B).…”

“…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]. A study in the North Atlantic right whale (Eubalaena glacialis) has demonstrated that FGCM concentrations are influenced by loud vessel noise or by animal entanglement in fishing gear [40,42,44].…”

Deiminated proteins and extracellular vesicles - Novel serum biomarkers in whales and orca

“…Roles for regulation of these pathways via post-translational deimination have not been investigated. Thyroid hormones have been studied in a range of whales and dolphins, including for evaluation of energetics and stress Hunt et al, 2019), as well as environmental pollution (Buckmann et al, 2011;Villanger et al, 2011;Hunt et al, 2017;Simond et al, 2019). PADs have been related to thyroid cancer (Guo et al, 2017) and deimination of histone H3 has been linked to autoimmune thyroid disease (Morshed et al, 2019), while physiological effects of deimination on thyroid hormone synthesis remain to be investigated.…”

A blubber gene expression index for evaluating stress in marine mammals

“…To address these challenges, methods for remote biopsy sampling (e.g. via a dart attached to a pole or deployed by crossbow) of marine mammals and hormone detection in a variety of other matrices, such as blubber, respiratory vapor and feces, have been actively developed ( Boggs et al , 2017 , Burgess et al , 2017 , Burgess et al , 2018 , Champagne et al , 2017 , Hunt et al , 2019 , Noren et al , 2012 ). However, hormone measurements often lack the sensitivity to identify recent exposure to a stressor and do not provide additional information on downstream consequences.…”