Dolphin Heart Health: Discoveries from Barataria Bay
For Dr. Cynthia Smith, listening to hearts is part of the job. Her patients, however, are dolphins. In 2016, while monitoring bottlenose dolphins in Barataria Bay, Louisiana, Smith and her team discovered something unusual. Instead of the classic “lub dub” heartbeat, many dolphins had an extra sound—a “lub dub shhh”—suggesting heart murmurs.
Investigating Dolphin Cardiology
Smith, Chief Medical Officer at the National Marine Mammal Foundation (NMMF), and her colleagues suspected a link between dolphin murmurs and oil cardiotoxicity, given findings from bird and fish studies after the Deepwater Horizon oil spill. Yet dolphin heart health had never been formally assessed. Even auscultation—the practice of listening to the heart with a stethoscope—had no established methods for dolphins.
To change this, the CARMMHA team (Consortium for Advanced Research on Marine Mammal Health Assessment) worked with U.S. Navy dolphins in San Diego Bay. These trained dolphins, some with medical records spanning 50 years, allowed researchers to perfect new field-ready cardiac techniques.
Developing New Techniques
- Auscultation: Researchers discovered the best listening position was on the dolphin’s left side, between the flippers, with six stethoscope placement points.
- Echocardiography: For the first time, portable ultrasound imaging was used to capture heart structure and valve function in dolphins.
Perfecting these methods required creativity. “We ruined a lot of stethoscopes with salt water in the process,” noted Dr. Barbara Linnehan, Deputy Director of Medicine at NMMF.
Findings from the Field
In July 2018, researchers applied these techniques to 34 dolphins in Barataria Bay. Remarkably, all dolphins exhibited murmurs. Comparisons with Navy dolphins and Sarasota Bay dolphins (unaffected by oil spills) revealed similar patterns, suggesting that murmurs may reflect the athletic strength of dolphin hearts rather than disease.
However, not all results were benign. Two dolphins in Barataria Bay showed signs of pulmonary hypertension—elevated blood pressure in the right heart—never before diagnosed in wild dolphins or whales. Additionally, these dolphins had thinner ventricular walls compared to their Sarasota Bay counterparts, hinting at chronic cardiac or pulmonary disease potentially linked to oil exposure.
Why Heart Health Matters
Dolphins rely on powerful hearts to chase prey at high speeds. Conditions such as pulmonary hypertension or weakened heart walls could significantly impact their survival. While many murmurs appear normal, other abnormalities raise concerns about long-term consequences of oil exposure on dolphin populations.
A Step Forward in Marine Medicine
These studies mark the first successful dolphin echocardiograms and auscultations in the wild. They highlight both the resilience and vulnerability of dolphins in oil-impacted environments. As Dr. Smith emphasized, without dedicated funding, dolphin heart health might have remained unexplored.
Further research will investigate links between cardiac abnormalities and oil exposure. For now, the ability to listen to and image dolphin hearts represents a breakthrough in marine veterinary science—and a critical step in protecting these intelligent, athletic animals.
