All photos/credit: in courtesy of Jessica Kendall

Jessica Kendall-Bar

Scripps Institution of Oceanography, University of California San Diego, San Diego, USA

Lessons from sleep in the deep: Records of seal sleep at sea reveal extreme sleep
duration flexibility

DOI: 10.1126/science.adl4885


The extreme sleep adaptations of marine animals can reveal clues to sleep’s function,
plasticity, and pathology. For my PhD, I designed a new submersible system for
electroencephalogram (EEG) recordings of wild northern elephant seals, Mirounga
angustirostris. Unlike fur seals and dolphins that sleep unihemispherically, seals sleep
bilaterally during deep dives (100-400 m), spiraling downward upon entering REM-
associated sleep paralysis.

Using this biomechanical signature of sleep, I wrote an algorithm to estimate sleep
from 334 time-depth records, creating a range-wide “sleepscape”. Across seasons,
seals transitioned from sleeping 10 h per day on land to 2 h per day for up to 295 days
at sea. This unparalleled sleep duration flexibility challenges assumptions of baseline
mammalian sleep requirements with implications for understanding sleep deprivation.


Dr. Jessica Kendall-Bar is a Schmidt AI in Science Postdoctoral Fellow at Scripps
Institution of Oceanography, UC San Diego originally from San Francisco, California,
USA. Her research combines engineering, data science, ecology, and visualization to
measure behavior and physiology of marine animals amidst a changing climate.

For her dissertation, she developed a non-invasive system to record and visualize the
first recordings of marine mammal sleep at sea published in Science. She is an award-
winning scientist, artist, and science communicator who designs data visualization
courses, large-scale exhibits, immersive analytical tools, and decision support tools.
Her data visualizations, published in local news outlets, The New York Times and The
Atlantic, have informed international policy in domains ranging from marine mammal
conservation to coral reef restoration.