Upside-down swimming behaviour of free-ranging narwhals

Rune Dietz*, Ari D. Shapiro, Mehdi Bakhtiari, Jack Orr, Peter L. Tyack, Pierre Richard, Ida Grønborg Eskesen, Greg Marshall

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

18 Citations (Scopus)

Abstract

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.

Original languageEnglish
Article number14
JournalBMC Ecology
Volume7
DOIs
Publication statusPublished - 1 Dec 2007

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