Elephant Seal Diving Physiology

Northern elephant seals have a unique diving behavior. Elephant seals can dive very frequently and for a long time. Female northern elephant seals make two foraging trips every year, and after breeding season they head out to the sea for two months before returning to the rookery to molt (Stephens, 2012). This is a very long time to be in the open ocean. These seals can go very far and for a long-extended time into the open ocean. This could be due to where they forage for food. Most northern elephant seals target one oceanographic feature in particular; a boundary zone between two large rotating ocean currents, or gyres (Stephens, 2012). Cold nutrient rich waters and the warmer water of the tropics mix which drives growth of a massive food web. This is an ideal spot for phytoplankton to thrive, which is how these large food webs are supported. This huge abundance of food could be why these seals are able to stay and travel so far. Northern elephant seals can withstand things like climate change because they are not dependent on any single foraging strategy (Stephens, 2012). This makes them extremely adaptable as they change their foraging strategies based on their environment. This could also be the same for their diving physiology. Being able to adapt to consume the most food the most efficiently would help explain why these seals are able to dive for so long and so far. They can consume and retain a lot of energy because of this.

The energy requirements of this species are surprisingly low. Particularly during pregnancy, energy requirements are 70-80% lower than expected for mammalian carnivores (Maresh, 2015). Elephant seals are very efficient at preserving and storing energy, which is remarkable. These values are lower than necessary to support basal metabolism in mammals of this size (Maresh, 2015). These seals use foraging strategies that use the least amount of energy to conserve as much as possible. Something to keep in mind is that these seals travel very far, which makes it hard to collect precise or accurate data of their foraging habits. This means that there is still a lot that is unknown as to exactly how they conserve so much energy and can travel so far even though they are so large and need to consume large amounts of food. To remain in positive energy balance, the energy acquired from foraging must exceed the energetic cost of foraging (Maresh, 2015). This is the most likely reason to why these seals can retain so much energy, as they are traveling far but to a very nutrient rich food environment. Flipper stroking was 24% lower during the long migrations (Maresh, 2015). Being as efficient as possible is important to the seals survival and to thrive, so the less movement the better. Being so efficient is essentially what makes this species so unique.

Foraging habits aren’t the only thing that is fascinating with these species. The tolerance to hypoxia is fascinating as they can function with low oxygen supply. This is amazing with such a large creature that goes so far out to sea, which requires a lot of aerobic activity. Data collected from elephant seals has shown that elephant seals routinely tolerate extreme hypoxemia during dives to completely utilize the blood O2 store and maximize aerobic dive duration (Meir, 2009). Their ability to maximize aerobic dive duration is important for longer dives and is part of what makes elephant seals so successful. Investigating adaptations to hypoxia in animals at high altitude, during hibernation, or in diving environments may provide insights to the understanding and treatment of clinical conditions (Meir, 2009). This ability is unique and is something that should be looked at further as it is an enigma to scientists. These seals have small surface intervals and long dive times to deep depths. The fact that they can do all of this with minimal oxygen in their blood is astonishing. Approximately two-thirds of the total body O2 store is in the blood (Meir, 2009). This explains why they can still maintain body function even though they are doing aerobic activity. This helps with achieving longer dive times and avoiding getting decompression sickness. These animals are very efficient and can really push their bodies to the limit. The study of elephant seal physiology could be very beneficial in the medical field and in understanding how animals adapt to hypoxia.

Works Cited

Maresh, Jl, T. Adachi, A. Takahashi, Y. Naito, De Crocker, M. Horning, Tm Williams, and Dp Costa.n 2015. “Summing the Strokes: Energy Economy in Northern Elephant Seals during Large-Scalen Foraging Migrations.” Movement Ecology 3:22

Meir, Jessica U., Cory D. Champagne, Daniel P. Costa, Cassondra L. Williams, and Paul J. Ponganis.n 2009. “Extreme Hypoxemic Tolerance and Blood Oxygen Depletion in Diving Elephant Seals.”n American Journal of Physiology-Regulatory, Integrative and Comparative Physiology 297:n R927–39.

Stephens, Tim. “Elephant Seal Tracking Reveals Hidden Lives of Deep-Diving Animals.” UC Santa Cruz News, 15 May 2012, news.ucsc.edu/2012/05/elephant-seals.html.

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