for National Geographic News
Digital snapshots from above the Arctic have helped a researcher spot declining narwhal populations. The narwhal—a small Arctic whale known for its six-foot-long (1.8-meter-long) tusk—has dropped in numbers by an average of 6 percent per year during the last 17 years, said marine biologist Mads Peter Heide-Jørgensen.
In Heide-Jørgensen's study, published in the April issue of Marine Mammal Science, he used aerial surveys of narwhals (Monodon monoceros) in 2001 and 2002 at their major summering ground in northwest Greenland. The biologist used two large-format digital cameras that continuously download images to laptop computers.
When the resulting photographs were compared to narwhal counts taken in the 1980s—the last time a species count had been conducted in this area—the results were surprising.
"We thought there was a good supply," said Heide-Jørgensen, a researcher for the Greenland Institute of Natural Resources.
In 2001 Heide-Jørgensen's aerial survey counted 360 narwhals over 324 square miles (840 square kilometers). In 2002, 566 narwhals were sighted in 853 square miles (2,200 square kilometers).
Hunting may be one reason for the narwhal's slow disappearance, Heide-Jørgensen said. Narwhals are hunted by local Inuit populations for their tusks, meat, and skin. The narwhal's skin is particularly valuable, as it has an extremely high vitamin C content, he said.
In addition, climate change and a growing halibut fishery may be playing a role in the changing numbers, Heide-Jørgensen said.
The Voyage of the Narwhal
The narwhal's tusk, a spiraling extension from a male narwhal's lip and upper jaw, is actually an overgrown tooth. While the tusk's primary use may be to attract or impress females, researchers have also witnessed males jousting with their tusks. There are also theories that the tusk may be used by narwhals as a way to sense sound or electromagnetic waves.
The narwhal has often been associated with another one-horned creature, the unicorn. In medieval times traders would pass narwhal tusks off as unicorn horns, thought to have magical disease-curing powers. Queen Elizabeth I reportedly paid 10,000 pounds for a single narwhal tusk in the 16th century—that's about what it would have reportedly cost to build an entire castle at the time.
"It's a very peculiar animal," said Heide-Jørgensen, who has been studying arctic marine mammals for 20 years. "We know very little about them."
To uncover a few of the narwhal's secrets, Heide-Jørgensen and Kristin Laidre, a research scientist at the University of Washington in Seattle, have been fitting the marine mammals with satellite tags. The tags help the researchers track narwhals' movements and behavior from a distance.
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