Researchers unravel the truth about the narwhal's living conditions by studying the bizarre porpoise tusks.
The Unicorn of the Arctic's tusks is built with individual layers that act as archives similar to tree trunk rings, revealing what the mysterious whale has eaten and how it has lived during its long life span.
What is a Narwhal?
The Monodon monoceros or narwhal is a carnivorous mammal that can grow up to 20 feet and weigh roughly 1.5 tons during its long life span of up to 50 years. The pale-colored porpoise is found in Arctic coastal waters and rivers in Greenland, Russia, Norway, and Canada.
Often dubbed as the unicorn of the Arctic, narwhals are bizarre and beautiful whales with iconic tusks protruding from its head.
The near-threatened narwhal's tusks, commonly found on males, are actually an enlarged tooth that has sensory capabilities due to roughly 10 million nerve-endings inside. Some members of the 80,000 population can have up to two tusks, while others can have none. Its spiraled tusks protrude from the head which can grow up to 10 feet long.
The Truth About the Narwhal's Living Conditions
An international team of researchers analyzed individual growth layers from 10 narwhals from North-West Greenland, publishing the study in the journal Current Biology entitled, "Analysis of narwhal tusks reveals lifelong feeding ecology and mercury exposure."
By analyzing mercury and stable carbon and nitrogen isotopes, researchers found out the truth behind what the whales have eaten during their lifetime, how ice affected their living conditions, and the impacts of potentially toxic compounds have changed over time.
Research shows that the narwhal's tusks offer valuable data on its living conditions starting the day it was born up to until it expires.
Rune Dietz, lead author and a professor from the Department of Bioscience, Aarhus University, Denmark, says that researchers were amazed that a single animal could contribute 50-year long-term data which will help researchers further understand the development of biological communities.
He adds that the data provided by the porpoise's tusks mirror the development of the Arctic.
Narwhal's, Climate Change, and Mercury Poisoning
Climate change and mercury poisoning are the top threats to the biggest Arctic predators. Jean-Pierre Desforges, co-author of the study and a post-doctoral research fellow explains that the bigger the animal and the higher it is on the food chain equates to the likeliness of high amounts of mercury poisoning and contaminants in the animal's body.
Researchers were able to trace the development via narwhal's tusks, wherein each layer the team measured traces of mercury as they measured stable isotopes of carbon and nitrogen.
The composition of carbon and nitrogen isotopes in the tusk's layers showed insight into the narwhal's diet and how plentiful the prey was.
Findings showed that the narwhal's of Northwest Greenland mirrors the general trend across the Arctic, where sea-ice is rapidly declining, changing the spatial distribution of sub-Arctic and Arctic fish.
Researchers also found that from 1990-2000, the bizarre porpoises accumulated small quantities of mercury due to their change in diet from halibut and Arctic cod to capelin and polar cod further down in the food chain.
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