Posted by “The Adventures of Pinny the Pinniped” By Eleanor Ransdell-Green & Jeremy Sanchez
Abstract:
The book “The Adventures of Pinny the Pinniped” tells the tale of a young elephant seal pup named Pinny, who must overcome his fears of diving in the ocean to survive and prepare for a long migration to Alaska. Pinny must not only learn to face his fears, but also utilize the physiological adaptations that an elephant seal has, including suppressing his body’s metabolism and maximizing the oxygen stores within his body, so that he can dive for as long as one hour in the ocean to forage for food. On this journey, Pinny meets other young Elephant Seal pups who become his best friends and who also embark on this journey with him, learning how to dive and forage in the ocean. This journey shows the ecology and physiological adaptations of elephant seals which makes them very efficient among mammals that dive in the ocean. The objective of this story is to help children understand aerobic metabolism and the seals’ utilization of oxygen to efficiently generate energy from food.
Written statement:
“The Adventures of Pinny the Pinniped” tells the story of a young juvenile Northern elephant seal named Pinny, who learns how to make deep dives into the ocean with the help of his friends and an old lone elephant seal that he encounters on the sunny beaches of Central California. Through this emotional, fun-filled story, children will learn about the importance of oxygen and its use in aerobic metabolism to convert food into energy for the body. Children will also learn how the rate of oxygen consumption via aerobic metabolism can be controlled by altering heart rate. Along with these objectives, readers will become familiar with the diving adaptations of elephant seals, as well as some of their feeding and migration patterns. To capture the attention of readers, the story is illustrated with colored pencil drawings depicting scenes of Pinny and his friends.
Northern elephant seals (Mirounga angustirostris) are considered to be the deepest-diving pinniped. These remarkable animals routinely dive to depths greater than 500 meters but have been known to occasionally dive to depths exceeding 1,500 meters. Elephant seals are known to spend 80-90% of their time underwater. Dive durations average approximately 20 minutes but have been known to last for as long as 90 minutes (Webb et al., 1998).
At 28 days old, young elephant seals are left behind by their mothers, and must learn to extend the time of their breath-holds and diving durations on their own (Thorson & Le Boeuf, 1994). The developmental period of an elephant seal is considered a critical time in which a young seal must build oxygen stores and enhance its ability to utilize these stores in a manner that will extend the time it spends in an aerobic state (Tift, 2011). To make long, deep dives, juvenile elephant seals work to increase the concentration of hemoglobin and myoglobin in their blood and muscle, respectively, allowing them to increase oxygen storage capacity by 47% (Thorson & Le Boeuf, 1994).
Previous studies have shown that, during a routine dive, elephant seals are capable of achieving O2 partial pressure (PaO2) values of 12-23 mmHg and O2 saturation (SaO2) values of 8%-26%. This demonstrates remarkable hypoxemic tolerance, giving them the ability to maintain aerobic metabolism during a dive instead of anaerobic metabolism (Meir et al., 2009).
Upon submergence, an elephant seal will decrease tissue oxygen delivery by reducing its heart rate by 50–80% from the SI value (Andrews et al., 1997). Data collected on juvenile elephant seals suggests that a blood volume of one-third arterial and two-thirds venous work to optimize loading and utilization of blood O2 stores during a dive. The contribution from venous O2 stores toward the total metabolic rate is greater than 100% of their estimated allometrically basal metabolic rate (Meir et al., 2009). These remarkable diving adaptations of the elephant seal are essential for successful foraging for squid and fish and will allow them to complete their long migration from Central California, all the way to the Aleutian Islands of Alaska (Le Boeuf et al., 2000). During their migration, male and female elephant seals tend to move north or northwest along the continental margins, to feed on benthic prey, such as fish, found in shallower waters. In contrast, female elephant seals will remain in deeper waters, and concentrate their feeding on pelagic prey, such as squid (Le Boeuf et al., 2000).