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Sleeping while diving: tools to detect, analyze, and visualize sleep in wild seals

Creative Commons 'BY-NC' version 4.0 license

Wild animals have evolved extreme physiological adaptations to balance the risks of starvation, predation, and exhaustion. Sleeping animals sacrifice food while vulnerable to predators. Marine mammals at sea balance the need to feed with the added challenge of surfacing to breathe, where predators lie in wait. Northern elephant seals (Mirounga angustirostris) travel thousands of kilometers, performing long dives to gather sustenance before returning to land to fast while they breed or molt. For my dissertation, I engineered a device that measures when, how, and how much these animals sleep at sea- the first recording of sleep in a wild marine mammal. Across their amphibious habitat, seals slept as much as 14 hours per day on land in the lab and as little as 0 hours per day at sea. Analytical methods derived from these results allow us to interpret hundreds of diving records over a 20-year dataset to find that seals sleep about 2 hours per day during >220-day foraging trips. At sea, elephant seals leverage their extreme breath-holding capacity to create a safe sleeping niche, up to 377 meters below the surface. I developed a process to transform data into animated 3D visualizations that display physiology alongside behavior. As new technology facilitates the collection of large ecophysiology datasets, we must also advance sensor technology, analytical workflows, and visualization techniques to better interpret this data. My dissertation creates and implements novel instruments and techniques that record, characterize, and visualize the physiology and behavior of wild animals to facilitate comparative neurophysiology research within conservation and translational medicine.

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