Estimating age and annual tooth growth rates in narwhals (Monodon monoceros) using computed tomography
The spiraling tooth of the narwhal (Monodon monoceros) has long intrigued scientists, but the growth rates of its "tusk" are poorly constrained due to the difficulty to age narwhal. To learn more about the population dynamics and life history of this exploited species, previous studies have used sectioned teeth to age narwhals and calibrate other ageing methods based on aspartic acid…
Scientists have long been fascinated by the spiraling tooth of the narwhal (Monodon monoceros), yet the growth rates of this unique tusk have remained poorly understood due to challenges in aging narwhals. Previous research relied on sectioned teeth and ageing methods based on aspartic acid racemization, radiocarbon analysis, or trace element analysis, but these approaches were limited by their destructive nature and the need to sacrifice the tooth.
In a new study, computed tomography (CT) was employed on five narwhal teeth as a non-invasive method to estimate the age of these animals, revealing distinct growth rates between erupted and embedded teeth during adolescence. Additionally, when combined with a reanalysis of all relevant literature, CT data provide clarity on the annual growth rates of narwhal tusks, which reach their peak before the age of 10, averaging approximately 100 mm per year.
This innovative approach holds promise for studying narwhal teeth in private and museum collections, potentially leading to more accurate estimations of age and growth rates. Furthermore, the findings may help refine the use of trace element proxies in narwhal teeth, contributing to more sustainable harvest management practices for this exploited species.
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