Past and present population dynamics of narwhals Monodon monoceros

• Main Author: Garde, Eva
• Format: Book
• Language: English
• Published: Faculty of Science, University of Copenhagen 2011
• Subjects: Arctic; Canada; Greenland; Beluga; Beluga whale; Beluga*; Climate change; Delphinapterus leucas; inuit; Monodon monoceros; narwhal*
• Online Access: https://curis.ku.dk/portal/da/publications/past-and-present-population-dynamics-of-narwhals-monodon-monoceros(1fb2c571-f9a3-4ebd-936a-c7b9fac52339).html

The narwhal, Monodon monoceros, is a medium-sized odontocete whale, endemic to the Atlantic sector of the Arctic and sub-Arctic. In both Canada and Greenland, subsistence hunting of narwhals by the Inuit has existed for centuries and still today the narwhals are hunted for their precious tusks, meat and mattak. Concerns have been raised about the sustainability of the hunt, which have led to implementation of hunting quotas in both countries. Hunting quotas are usually calculated from population dynamics models where survival and reproductive rates, based on reliable age distributions, are vital. Estimation of life history parameters for the narwhal has previously been hindered by lack of a reliable age estimation technique. The Aspartic Acid Racemization (AAR) technique is a relatively novel method that I have applied to narwhals. This PhD thesis focuses, in part, on current population dynamics and life history of the narwhal by estimating life history parameters and creating age distributions using the AAR technique. The thesis includes several studies involving the application of AAR in age estimation. We conclude that the AAR technique is indeed a reliable method for age estimation of both marine and terrestrial mammals, although the technique still requires both optimization and further validation. In addition, the thesis includes a study of past population dynamics in narwhals. We have investigated the genetic response to climate change and the emographic history of the narwhal through analysis of ancient and modern mitochondrial DNA (mtDNA). Very low levels of genetic diversity have been observed in modern narwhals from Canada and Greenland, resembling that of species that have endured through severe bottlenecks. The hypothesis is that the current narwhal populations were founded from only few individuals relatively recently. Using samples collected over the past and present geographical ranges of narwhals, representing a time series from several thousands years ago and until today, we detect long-term low genetic diversity in the narwhals extending as far back in time as 50.000 years. The results are compared with results from the beluga whale, Delphinapterus leucas, revealing two very different demographic histories.