Brookfield Zoo Chicago (BZC) proudly operates the Sarasota Dolphin Research Program (SDRP), the longest-running study of a free-ranging dolphin population. The knowledge gained by studying these bottlenose dolphins has informed our husbandry/care practices at the Zoo. Furthermore, the research conducted with the dolphins residing at Seven Seas helps us better understand the behavior and health of wild populations. One of our current projects involves investigating phthalate levels for the dolphins living at BZC and making comparisons with wild dolphins.
What are phthalates? Phthalates are manmade chemicals that are added to cosmetics, pesticides, cleaning products, plastics, and personal care products. Unfortunately, these chemicals are commonly found in marine environments and pose a risk to wildlife. Indeed, there is evidence that chronic exposure can lead to hormone disruption, which can impact growth, development, and reproduction. In humans, phthalate exposure may even be associated with an increased risk of cancer.
Why examine phthalate exposure in bottlenose dolphins? Dolphins have a long lifespan and are top-level predators. Therefore, they can serve as “gauges” or “sentinels” that help us predict pollution risks for other aquatic species, as well as humans. Unfortunately, recent studies of the Sarasota Bay population reported that 70-75% of the dolphins who were sampled had detectable levels of phthalates. These studies included subjects of various age-sex classes (i.e. males and females representing a wide range of ages).
Why study phthalate levels in the dolphins living at Brookfield Zoo Chicago? Fortunately, the dolphins who reside at Seven Seas willingly participate in veterinary exams and allow us to collect various types of samples. Phthalate levels can be assessed by analyzing urine samples. Our first goal will be to compare if/how phthalate levels differ between wild dolphins and dolphins at BZC. Unlike Sarasota Bay, the Zoo is a controlled environment, so we know that no chemical dumping or runoff of phthalates is occurring. Therefore, if detectable levels of phthalates are found for the dolphins at BZC, we will have to consider potential sources. Furthermore, while studies on wild dolphins have typically involved collecting a single urine sample from each subject, zoo researchers can collect multiple samples over a relatively short period of time. This will allow us to determine how long it takes for phthalates to return to undetectable levels, if phthalates are indeed detected. This is important, because we can get an idea of how long it takes for dolphins to process and excrete these chemicals (health issues may be less likely to occur with faster excretion rates).
Please keep an eye out for updates regarding this project! Within the next several months, we should have much more knowledge regarding phthalates in both wild dolphins and those who reside at BZC!
Dr. Jessica Whitham
Animal Welfare Biologist
Published August 6, 2024