Dolphin Stress During Capture-Release Health Checks
Cetaceans, including dolphins, are increasingly under threat from both “natural” and anthropogenic (human-caused) factors. Whether it is climate change, pollutants, algae blooms, ship traffic or noise, fishing, or other disruptions, the threats to cetaceans are varied and serious. Fortunately for them, dolphins are of particular concern to the general public as well as conservation groups and government authorities. The Dolphin Health and Risk Assessment Project (HERA) is described as “a multidisciplinary, integrated, collaborative effort to assess the health of coastal dolphin populations using standardized procedures.” The HERA project looks at the health of wild dolphin populations through regular capture-and-release health assessments to try to determine the status of cetacean populations in different areas of the U.S.
While the HERA project is arguably an important initiative, capture-and-release programs may inadvertently and unnecessarily raise stress levels of dolphins (and other animals) when gathering data. In turn, this can skew the results of such studies. This study reviewed attempted to assess how much dolphins are stressed during the process by measuring cortisol levels. The study found “significant temporal effects” on cortisol levels in dolphins, and that there was also “considerable inter-species variability in hormone concentrations.” In other words, many factors such as age, sex, habitat, and exposure to disturbances can have an effect on stress hormones, making them less than ideal as metrics.
The process of measuring stress levels in dolphins is itself another factor that makes measuring stress difficult. The researchers acknowledge this, saying that “our understanding of stress and responses” has progressed over the years, but that it “remains difficult to study stress in these animals.” For animal advocates, this study (and others like it) show that there is inherent difficulty in understanding stress in animals, especially wild animals. Moreover, when it comes to sensitive species, we should be especially careful with how we proceed in our efforts to ensure their welfare and preserve the species.