The Physiology of Marine Mammals

I was on a one-day deep sea fishing trip off the coast of Southern California and the topic of diving mammals came up as we were watching sea lions swim around our boat. They must have been attracted to the same school of fish we were trying to catch. I must admit they were more successful at catching fish that day than we were! Their ability to dive and fish in deep waters, which would require an oxygen tank for a human to attempt, was nothing short of impressive. Curious to learn more, I searched for information on The APS website and came up with an interview between Andreas Fahlman and APS staff on this issue. In this podcast, Dr. Fahlman discusses the unique adaptations of diving mammals that allow them to dive deeper and stay in the water longer than humans. For humans, the lungs are critical in the delivery of oxygen to red blood cells, which transport it to tissues throughout the body, and we have a limited ability to store oxygen. In contrast, these diving mammals have almost 3 times the blood volume, more red blood cells and more myoglobin compared to humans. The excess myoglobin in muscles allows them to store oxygen for use during the dive so that circulating oxygen can be spared for use by vital organs. To further prevent complications from the low oxygen conditions, diving mammals constrict their peripheral blood vessels to ensure adequate blood flow to the essential organs.

Click here to listen to the podcast.