Stereotypical resting behavior of the sperm whale

• Published in: Current Biology
• Main Authors: Miller, Patrick, Aoki, K., Rendell, Luke Edward, Amano, M.
• Format: Article in Journal/Newspaper
• Language: English
• Published: 2008
• Subjects: SLEEP; ASYMMETRY; Physeter macrocephalus; Sperm whale
• Online Access: https://research-portal.st-andrews.ac.uk/en/publications/0b519f39-c159-45d3-b195-034afbd59cd5; https://doi.org/10.1016/j.cub.2007.11.003; http://www.scopus.com/inward/record.url?scp=37449002623&partnerID=8YFLogxK

Though very little is known about sleep in wild cetaceans, toothed cetaceans in captivity sleep with one side of their brain at a time [1]. Such uni-hemispheric sleep is thought to enable swimming, voluntary breathing, predator avoidance and/or social contact during sleep at sea 2 and 3. Using suction cup tags, we discovered that sperm whales (Physeter macrocephalus) worldwide conduct passive shallow ‘drift-dives’ in stereotypical vertical postures just below the sea surface. Bouts of drift-dives accounted for 7.1% of recording time, or 36.7% of non-foraging time. Drift-dives were weakly diurnal, occurring least from 06:00–12:00 (3% of records), and most from 18:00–24:00 (30% of records). A group of vertically drifting whales were atypically non–responsive to a closely-passing vessel until it inadvertently touched them, suggesting that sperm whales might sleep during these stereotypical resting dives.