Dolphins are air breathing, diving mammals that hold their breath to find food. The amount of food they can obtain depends partly on how long they can hold their breath. Lung disease is therefore a significant problem as it both causes health issues and reduces foraging efficiency. In Sarasota, Florida, the shallow bays provide food at shallow depths and dive durations can be relatively short. The pelagic dolphins in Bermuda, on the other hand, dive up to 1,000 m (more than 3,000 ft) and as they have to swim a much longer distance to the food, dive durations of more than 13.5 minutes have been recorded.
To better understand the physiological adaptations that allow dolphins of the same species to inhabit such divergent habitats and ecological niches, we wanted to compare lung function between the Sarasota Bay and Bermuda dolphins. To do this, we used a custom designed device (called a pneumotachometer) that measures the amount of air the dolphins are inhaling and exhaling, and also measures the concentration of oxygen and carbon dioxide in their breath. Together, the flow and gas concentration are used to determine the metabolic rate. In addition to metabolic rate, we can use these measurements to assess lung health and better understand the adaptations that allow the Bermuda dolphins to dive to depths where the extreme pressure may cause trauma to air filled spaces like the lung. We also use ultrasound to examine the condition of the lungs. The procedures we use to assess lung function are similar to those used to assess the health of human lungs. If we see large differences in lung health in the dolphins in Sarasota and Bermuda, this may indicate there are problems in the ecosystem. By comparing respiratory health in different populations of dolphins, we can learn more about the health of those populations and the marine environment in which they live. Analyses are underway, and we are specifically looking at comparing the respiratory tidal volumes, which at least preliminarily seem to be larger for Bermuda dolphins than for those of the dolphins in Sarasota Bay. Funding was provided by Dolphin Quest and through an Office of Naval Research YIP award (#N000141410563).
This article appeared on pages 14-15 of the 2017 SDRP Annual Report, Nicks n Notches.