Abstract

Narwhals (Monodon monoceros) are medium sized toothed whales which hold great cultural significance to the Inuit of Canada’s eastern Arctic. Baseline health information is lacking for this iconic species, and they are considered to be at high risk for negative population impacts from ocean warming and associated disturbance¹. They are listed as a “Species of Special Concern” in Canada², and information about population trends is sparse³. Narwhals have a range limited to ocean waters north of 60 degrees latitude, with the largest concentrations found in remote Arctic waterways in eastern Canada and western Greenland². Climate, geography, sparse human population and scavengers limit access to any stranded narwhal carcasses, so the authors collaborated with local hunters from the Mittimatalik Hunter and Trapper Organization (Pond Inlet, NU) during two summers to conduct necropsy examinations on 13 traditionally harvested whales (10 adult: 3 juvenile or subadult; 5 male: 8 female). Review of gross and histopathological findings reported here forms one aspect of a broader health assessment of these individual whales for changes related to disturbance, nutrition, aging, injury, neoplasia and pathogens. A comprehensive range of tissue samples were collected from each whale, preserved in formalin and examined for microscopic abnormalities. All animals examined were judged to be in good body condition based on blubber thickness, however histologic changes in the liver indicative of atrophy led to a conclusion that these animals are not meeting nutritional energetic requirements while close to shore in July and August. All animals exhibited aural and pulmonary parasitism involving Halocerus sp. nematodes with associated multifocal inflammation. Multifocal myodegeneration and scattered tissue bradyzoites (suspected Sarcocystis sp.) were present in skeletal muscle and myocardium. One mature male had a chronic fracture and exuberant callous of the maxillary bone at the base of the tusk. Several neoplastic changes were identified including pulmonary chondrosarcoma, pancreatic duct adenoma, adrenal lipoma, intestinal leiomyoma, and epidermal papilloma. One animal had extensive hepatic fibrosis with biliary hyperplasia. Reproductive examination documented normal lactation in some females, and inactive mammary glands in others. Recent ovulation, active uterine involution, and paucity of ovarian follicles were identified in different females and extend our knowledge of the reproductive life of the narwhal. Examination of these 13 animals is providing new information on the biology, diseases and aging of narwhal, which can be used for comparison to other populations, and begins to lay the groundwork for a health baseline for Monodon monoceros.

Acknowledgements

The authors would like to acknowledge the assistance of The Mittimatalik Hunters and Trappers Association, and the many hunters and elders from the community of Pond Inlet, without whom this work could not have proceeded. These include Caleb Sangoya, Jonas Kiliktee, Andrew Jaworenko, Caleb Sangoya, Sam Omik, Hammy Quaraq, Simon Komagapik, Nyman Pewatoalook and Mishal Pewatoalook. In particular assistance and mentoring by Mr. Jack Orr were of paramount importance to this work.

Literature Cited

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2.  COSEWIC 2004. COSEWIC assessment and update status report on the Narwhal Monodon monoceros in Canada. Committee on the Status of Endangered Wildlife in Canada; Ottawa, Canada.

3.  Witting L. 2016. Meta population modeling of narwhals in East Canada and West Greenland. Canada-NMMPRC 2016 October: 1–20.