Sea Otter Metabolics and Thermoregulation
Sea Otters (Enhydra lutris) have always intrigued me because they are one of the most recent additions to the marine environment having only been fully aquatic for about 1-3 million years, but what really peaked my interest was the fact that they maintain homeostasis as far north as Alaska without blubber in 13-17 degree water, and that the metabolic rate that they would have to have must be enormous so I decided to look into what it takes to keep an otter running in such cold water, especially when you consider how big the difference is between their core temperature and the temperature of their surroundings. The amount of caloric intake required combined with how much oxygen they use during their main activities could tell us a lot about what it takes to live in such an unyielding and unforgiving environment. But by learning how much energy they use and how they use it we could learn a lot about
We measure how much energy it takes an otter to do something by measuring the oxygen consumption during surface behaviors, and the oxygen consumption after an otter returns from a dive. This is done using a small plastic dome put around the animal, and it measures the amount of oxygen which is then divided by the time the activity takes to make the Oxygen Consumption Rate. This has been used to show that sea otters have resting metabolic rates that range from 2.8 to 3.2 times that of a similar sized terrestrial mammal (Iverson, 1972; Morrison et al., 1974; Costa, 1978; Costa and Kooyman, 1982). Even though we expect marine mammals to have a high metabolic rate, this represents an extreme. So what does an otter spend its time doing? So otters spend their time in this breakdown: 36.3 % feeding, 40.2% resting, 8.5% Swimming, 9.1% resting, 7.3%other (Yeates, Willams, Fink 07). This tells us what is important to the life of the sea otter; It’s obvious from spending a third of its life feeding that it takes a huge number of...
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