Acknowledgements
We thank the Office of Polar Programs and Division of Integrative Organismal Systems at the National Science Foundation, Harvard Schools of Medicine and Dental Medicine, the Marine Mammal Program at the Smithsonian Institution, the Arctic Research Division of Fisheries and Oceans, Canada (DFO), Aarhus University, Greenland Institute of Natural Resources, and the high Arctic communities of Arctic Bay, Pond Inlet and Repulse Bay for their continued support of field work.

Among the collaborating institutions are the Paffenbarger Research Center at the National Institutes of Standards and Technology, the Explorers Club, World Center for Exploration, Sea World San Diego, the National Institutes of Health Imaging Department, Webb Research, Woods Hole Oceanographic Institute (WHOI), the Johns Hopkins
For the analyses and interpretation of electrocardiogram data, we thank physician Michael Parker and Shahin Tahery, Senior Technician and Trainer at Midmark International. For extensive library searches of foreign and obscure published accounts of the narwhal, our thanks to Mary Sears at the Ernst Mayr Library of the Harvard Museum of Comparative Zoology; Keiko Meshida, Rare Books Collection, Vertebrate Zoology Library, Smithsonian Institution; and David Osterber at Countway Library, Harvard Medical School. We thank the following individuals for their assistance and collaboration: William Fitzhugh, Arctic Studies Center; Judy Chupasko and Mark Omura, Division of Mammals, Harvard Museum of Comparative Zoology; Greg Marshall and Mehdi Baktiara of NGS; Evelyn Flynn and Lisa Marie Leclerc, Boston Children’s Hospital; Joseph Paradiso, Medialab,
Medical School Imaging Department, the Nunavut Wildlife Management Board, the Polar Continental Shelf Project, the National Geographic Society (NGS), Sunstar Butler, Castle Harlan Corporation, Harvard Museum of Comparative Zoology, Arctic Research Center Smithsonian Institution, the University of Copenhagen Zoological Museum, the Forsyth Institute, the Canadian Museum of Nature, Grass-Telefactor, Astro-med, Inc. and Midmark International.

Funding for field research and laboratory analysis was provided by grants 0922052, 0839989, 0739858, from The Neural Systems Cluster of the Division of Integrative Organismal Systems at the National Science Foundation, Harvard Schools of Medicine and Dental Medicine, Harvard Museum of Comparative Zoology and Smithsonian Institution.
 
Massachusetts Institute of Technology; Clint Wright, Vancouver Aquarium; Pierre Richard, Arctic Research Division, Fisheries Oceans, Canada; Leslie Parr, San Jose State University, and her graduate evolutionary biology class; Pete Ewins, World Wildlife Fund; Francis Thackeray, University of the Witwatersrand, Johannesburg; Darlene Ketten, WHO; Ari Shapiro, MIT; Keith Yip, Seaworld San Diego; Hans Christian Schmidt; Jim (Wolverine) Orr; Jessie Shooyook; Frank McCann and Joseph Guay (DFO); videographers Adam Ravitch and Henrik Egede-Lassen; and research assistants Katherine Tiisler, Nancy Stabley, Amy Jordan, Janet Kurland, Judy Moran, and Benjamin Gray Jr., Narwhal Tusk Research.

Support for the collection, translation and interpretation of Inuit traditional knowledge was provided by grants 0756708, 0701534, 0646872, 0630561 from the Office of Polar Programs, NSF.