Killer whale fecal samples: How to get the most out of a single extraction

Fecal samples are a non-invasive and relatively accessible matrix for investigating physiological processes in resident killer whale (Orcinus orca) populations. The high lipid content of the diet (primarily salmonids) leads to lower density fecal material and slower dispersion, facilitating sample collection. As fecal discharge is relatively infrequent and the volume of sample is variable, maximizing analytical options is an important consideration. Here we present an extraction methodology to measure hormones and lipid content from the same fecal aliquot. Lipid extractions are commonly conducted using chloroform and methanol from Folch or Bligh and Dyer (B&D), while alcohol is the primary solvent for hormone extraction. We evaluated the possibility of using the methanol layer from lipid extractions to assess fecal steroid hormone levels. Folch and B&D methanol residues were assayed form metabolites of progesterone (PMs) and corticosterone (GCs), and results were compared to aliquots extracted in 70 % ethanol. Hormone concentrations measured in the methanol layer from Folch and B&D extractions were 55 % to 79 % lower than concentrations in 70 % ethanol. We developed mathematical corrections, using linear regression models fitted to Folch or B&D methanol vs 70 % ethanol hormone concentrations (p < 0.01). Fecal concentrations of PMs and GCs from methanol extractions were biologically validated and are significantly higher in confirmed pregnant females compared to non-pregnant individuals (p < 0.05). This study demonstrates that lipid extraction protocols may be used for the analysis of multiple biomarkers, maximizing the use of small-volume samples.

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

In waters off Península Valdés (PV), Argentina, southern right whales (SRW, Eubalaena australis) are occasionally exposed to domoic acid (DA), a neurotoxin produced by diatoms of the genus Pseudo-nitzschia. Domoic acid toxicity in marine mammals can cause gastrointestinal and neurological clinical signs, alterations in hematologic and endocrine variables, and can be fatal in extreme cases. In this study, we validated an enzyme immunoassay to quantify fecal glucocorticoid metabolites (fGCm) in 16 SRW fecal samples from live and dead stranded whales in PV from 2013 to 2018 and assessed fGCm levels associated with DA exposure. Overall, fGCm levels were significantly lower in SRWs with detectable fecal DA (n = 3) as compared to SRWs with undetectable fecal DA levels (n = 13). The highest fecal DA was observed in a live lactating female, which had low fGCm compared to the other lactating females studied. The highest fGCm was observed in a lactating female with undetectable DA; interestingly, at the time of sample collection, this female was sighted with two calves, an extremely unusual occurrence in this species. Though the sample size of these exceptionally rare breeding-season fecal samples was unavoidably small, our study provides evidence of potential adrenal alterations in whales exposed to an environmental neurotoxin such as DA.

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

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.

Reproductive hormone monitoring of dugongs in captivity: detecting the onset of sexual maturity in a cryptic marine mammal

Determining the reproductive status of long-term captive animals is essential because the onset of sexual maturity and reproductive activity may necessitate changes in husbandry requirements. This study reports on the first multi-year reproductive hormone monitoring program for captive dugongs of both sexes using feces. Fecal samples were collected from one male (Pig) over 9 years (4-13.2y of age; n=288 samples, 0.8±0.1 samples per week from July 2007 to February 2012) and one female (Wuru) over 7 years (from neonate to 6.9 y; n=171 samples, 0.5±0.1 samples per week from July 2007 to February 2012), and from one solitary female dugong (Gracie) over 10 months (10.5-11.3y of age; n=54 samples, 1.1±0.2 sample per week from September 2008 to June 2009). Using enzyme-immunoassay, fecal progesterone (fP) and estradiol-17β (fE) concentrations were assayed in the two captive females, and testosterone (fT) concentration in the captive male, and compared these to concentrations in wild dugongs. Female Wuru exhibited increasing fP concentrations at 5+ y, indicating early onset of ovarian cycling typical of non-pregnant adult females. Female Gracie maintained basal fP concentrations consistent with wild immature dugongs, indicating that she had not reached puberty by 11y. Nutritional plane may account for differences in age at sexual maturity in these female dugongs. At age 3-4y, Wuru had fE concentrations 1.4 times greater than maximum concentrations recorded in all wild females, and these concentrations were coincident with a period of rapid weight gain. For the male Pig, increasing fT concentrations at 9y provided early indications of puberty. Pig's tusks erupted by 11y, and sexual maturity (indicated by spermatic semen) was confirmed by 12.8y. Identification of sexual maturation prompted two trials of a male contraceptive treatment using the GnRH agonist, deslorelin (9.4mg administered in 2010 and 15.6mg in 2011). Testosterone production was not significantly suppressed by these dosages, and treatment did not terminate sperm production at week 10-11 post-implantation, even at the larger dose tested. Routine analysis of fecal hormones was helpful for making reproductive management decisions regarding individual captives and in guiding the long-term captive management of this cryptic species.