Upside-down swimming behaviour of free-ranging narwhals

• Published in: BMC Ecology
• Main Authors: Dietz, Rune, Shapiro, Ari D., Bakhtiari, Mehdi, Orr, Jack, Tyack, Peter L., Richard, Pierre, Eskesen, Ida Grønborg, Marshall, Greg
• Format: Article in Journal/Newspaper
• Language: English
• Published: 2007
• Subjects: Admiralty Inlet; Canada; The Tusk; Monodon monoceros; narwhal*
• Online Access: https://risweb.st-andrews.ac.uk/portal/en/researchoutput/upsidedown-swimming-behaviour-of-freeranging-narwhals(43b327c7-0c24-448f-b810-d1d27114dfff).html; https://doi.org/10.1186/1472-6785-7-14; http://www.scopus.com/inward/record.url?scp=38949092085&partnerID=8YFLogxK

Background. Free-ranging narwhals (Monodon monoceros) were instrumented in Admiralty Inlet, Canada with both satellite tags to study migration and stock separation and short-term, high-resolution digital archival tags to explore diving and feeding behaviour. Three narwhals were equipped with an underwater camera pod (Crittercam), another individual was equipped with a digital archival tag (DTAG), and a fifth with both units during August 2003 and 2004. Results. Crittercam footage indicated that of the combined 286 minutes of recordings, 12% of the time was spent along the bottom. When the bottom was visible in the camera footage, the narwhals were oriented upside-down 80% of the time (range: 61 100%). The DTAG data (14.6 hours of recordings) revealed that during time spent below the surface, the two tagged narwhals were supine an average of 13% (range: 9-18%) of the time. Roughly 70% of this time spent in a supine posture occurred during the descent. Conclusion. Possible reasons for this upside-down swimming behaviour are discussed. No preference for a clockwise or counter-clockwise direction of roll was observed, discounting the possibility that rolling movements contribute to the asymmetric left-handed helical turns of the tusk.