Just as in humans, it is possible to learn about a dolphin’s health from physiological biomarkers measured in their blood. However, blood sampling is a medical procedure that requires careful handling of animals in controlled conditions, which can be challenging and untenable in some field research applications. Feces and saliva, like blood, are composed of biological compounds that may serve as biomarkers of health and can provide a less invasive and potentially more feasible method for monitoring health in some wild cetacean populations and for animals under professional care.
Our team is developing methodology to identify and measure various biomarkers of health in feces and saliva from the bottlenose dolphin population in Sarasota Bay, and from a group of bottlenose dolphins under professional care residing at the Chicago Zoological Society’s Brookfield Zoo in Illinois. Given heightened concern over the exposure of marine mammal populations to various anthropogenic stressors (contaminants, vessel noise, etc.), many recent research efforts have focused on understanding stress physiology of cetaceans, including investigations on mineral- and gluco- corticoid hormones that reflect adrenal activity (indicative of the stress response) in both feces and saliva. We are building on this foundational research by expanding the suite of targeted biomarkers to hormones and immune factors that may serve as indicators of coping resiliency in addition to those indicative of both acute and prolonged stressed states. The steroid dehydroepiandrosterone (DHEA), while a precursor to male and female sex hormones, can also play a role in the physiological stress response in some species. DHEA has been shown to serve as a neuro-protector against the damaging effects of circulating glucocorticoids released during a stress response, and both human and non-human animal studies have shown a positive association between DHEA levels and coping resilience to stressors. Additionally, reduction in secretory immunoglobulin-A (s-IgA), secreted in both saliva and the intestinal mucosa, has been suggested as an indicator of prolonged stress in a number of species.
To date, we have collected 41 saliva and 4 fecal samples from Sarasota Bay dolphins and 200 saliva and 100 fecal samples from animals at the Brookfield Zoo across 2015 and 2016. Currently, we are assessing methods to identify the targeted biomarkers in bottlenose dolphin feces and saliva through enzyme immunoassay analysis. Additionally, we are running physiological validations by examining the correlation between blood and fecal/saliva values and biological validations by assessing concentrations of targeted biomarkers in response to observations of both positive and negative behaviors and social interactions. Ultimately, information from this research will inform animal care management of dolphins in zoos and aquariums to optimize welfare in these animals. Additionally, insights and methodology developed from this research may increase understanding of the resilience and coping effectiveness of wild dolphin populations that experience different exposures to anthropogenic stressors.
This article appeared on page 14 of the 2017 SDRP Annual Report, Nicks n Notches.