You have likely seen one at an aquarium. It is the friendly creature with the oversized head that swims up to the glass with what looks like a smile on its face. Beluga whales are extremely social mammals that are often called sea canaries because of their high-pitched chatter, or melonheads for the enlarged and flexible area above their eyes that creates facial expressions. These distinguishing features of the beluga whale make up just some of its unique characteristics. At the subject of much debate, however, is the whale’s teeth when it comes to determining its age.
A new collaborative study published by researchers at 91ֿ and Northeast Ohio Medical University (NEOMED) provides evidence that the thick layers - called growth layer groups (GLGs) - preserved in the teeth of beluga whales, may be just as reliable for measuring age as it is in other whale species. Much like counting rings of a tree trunk, researchers say beluga whales deposit one layer per year, providing an easy, visual marker.
Growth layer groups refer to a layer of dentin —the type of hard, bony tissue that lays below the enamel in our teeth. Beluga and sperm whales have particular cavities in their teeth that allow for continuous dentin deposits throughout their lifetimes. This distinction has for decades complicated the process of determining age in those species.
“Some scientists felt the standard measurement (one growth layer group per year) did not apply to Belugas, which made age estimation difficult,” said Joseph D. Ortiz, Ph.D., professor and assistant chair in the Department of Geology in 91ֿ’s College of Arts and Sciences. “The alternative model thought that Belugas laid down two growth layer groups per year.”
Dr. Ortiz teamed up with researchers David A. Waugh, and J. G. M. 'Hans' Thewissen, professor of anatomy at NEOMED, along with Robert S. Suydam, senior wildlife biologist for the North Slope Borough Department of Wildlife Management in Utqiaġvik, (Barrow) Alaska. Together they studied tooth samples taken from whales in the Chukchi Sea (north of the Bering Sea, between Russia and Alaska).
“The way that we were able to resolve this was to document that the beluga whales also laid down thin, daily layers that make up the dentin in each GLG, which we could then show are annual growth layers,” Ortiz said. “I helped to quantify the trends in the data and the statistical significance tests we applied,” Ortiz said.
Beluga whales are thought to live roughly 60 to 70 years in the wild in both Arctic and Subarctic waters. As their Arctic environment continues to change at a rapid pace, it is imperative to better understand beluga’s life history.
As part of 91ֿ’s ongoing commitment to drive research to enhance the quality of life, this latest study is the first of its kind to confirm annual banding in beluga teeth by comparing against daily layers. The results show that these two were internally consistent, resolving the question of how much time each band represents.
The is published in the open-access journal PLOS ONE.
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Photo Caption:
A new collaborative study published by researchers at 91ֿ and Northeast Ohio Medical University provides evidence that the thick layers - called growth layer groups - preserved in the teeth of beluga whales - may be just as reliable for measuring age as it is in other whale species.
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