Climate change is affecting everybody, even narwhals. These mysterious “unicorns of the sea” may decline by 25% by the end of this century, according to a new study.

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Narwhals are a type of Arctic-dwelling whale found only in the cold waters of Greenland, Canada, Norway and Russia. Their population currently numbers about 200,000. In winter, most narwhals spend up to 5 months beneath the sea ice. They are recognizable by a single long, spiral tusk, which is actually an enlarged tooth.

Related: Arctic shipping routes could threaten “unicorns of the sea”

Researchers from Denmark, Canada, Norway, Germany and the U.K. studied tissue samples from 121 narwhals, mostly collected between 1982 and 2012. Some were killed by Inuit hunters in Greenland and Canada. Other samples came from archaeological remains from digs in Russia and northern Europe. Researchers were even able to collect tiny samples from a throne chair featuring narwhal tusks in Denmark.

“They had special access to be able to drill little tiny bits of tusk from that throne,” said Steven Ferguson, an Arctic marine mammal research scientist with Fisheries and Oceans Canada and one of the study’s authors. These samples helped them learn more about narwhal DNA. Through a combination of DNA information and habitat modeling, the researchers investigated the impact of previous climate shifts on narwhal distribution and estimated what the future might hold for these creatures.

Scientists confirmed that the world has three narwhal populations. Most live in two different groups off Canada’s northeastern coasts. The third population of about 10,000 lives off Greenland’s east coast, extending as far as Russia. The researchers were surprised to find that narwhals show the lowest genetic diversity in any marine mammal studied. They weren’t sure why this is.

As sea ice melts because of global warming, the narwhals’ habitats will shrink, and the animals will probably move northward. But as they are crowded into a smaller habitat, they’ll become more vulnerable to human encroachment, competition for food, new diseases and orca predation. Unlike other polar mammals, narwhals are only found in very limited locales. “They really seem to have this Atlantic Ocean habitat,” Ferguson said. “So there’s an open question as to what might happen as we continue to lose sea ice.”

+ Royal Society Publishing

Via Forbes and The Narwhal