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A critically endangered Hawaiian monk seal sits on the sands of the French Frigate Shoals in the northwestern Hawaiian islands.



Monk Seal Evolution Rewritten: Dwindling Animals "Even Rarer"

Study reveals a new branch on the monk seal family tree.

Scientists have discovered a new genus of monk seal, according to a new study—the first in the modern seal family in more than 140 years.

The new branch of the family tree, Neomonachus, means that species of living monk seals are more distantly related than previously thought—and that the stakes for saving the rare creatures are even higher.

There are three known species of monk seal, all of which were thought to belong to the genus Monachus: the Hawaiian, Mediterranean, and Caribbean. The latter went extinct in the 1950s due to hunting and other causes related to humans. (Related: "Crittercams and Crowdsourcing to Solve Mystery of Hawaiian Monk Seals?")

The two living species are critically endangered: The Hawaiian seal, found throughout the Pacific island chain, numbers about a thousand animals; and the Mediterranean seal, which lives in the southeastern Atlantic Ocean and the Mediterranean Sea, has dwindled to between 350 and 450 animals.

Though threats to the large marine animals differ, most of their decline is due to the impact of humans—ocean pollution and destruction of coastal habitats, for instance, as well as the deployment of fishing gear that entangles the seals.

To save the two species from extinction, scientists want to know as much as they can about them, including their evolutionary relationship to the extinct Caribbean monk seals.

Until recently, that was "a riddle that had gone unanswered," mainly because few high-quality museum specimens of Caribbean seals exist, said study co-author Kristofer Helgen, curator of mammals at the Smithsonian's National Museum of Natural History in Washington, D.C.

DNA Detective

But Helgen and his colleagues had a home-team advantage: the Smithsonian Institution's collection of monk seal pelts, which are the best preserved in the world.

Helgen, who's known for his DNA detective work in unveiling the raccoon relative known as the olinguito in 2013, extracted genetic material from the pelts and examined and compared skulls of all three species.

According to the study, published May 14 in the journal ZooKeys, the results were clear: Caribbean and Hawaiian monk seals belong to a separate, newly named genus—Neomonachus.

That means the Mediterranean monk seal, which remains in the Monachus genus, is only distantly related to the Caribbean seal, not closely related as previously thought.

The new genus discovery is the "most exciting from the classification perspective, because [for] animals as large as these, changes don't happen very often," said Helgen, who is also a National Geographic emerging explorer.

Indeed, this is the first time in more than 140 years that a new genus has been recognized among modern pinnipeds, a group that includes seals, sea lions, and walruses. (See a map of pinnipeds around the world.)

Going from a "coarse understanding" of monk seal history to a much sharper one is admirable, and is "such a great example of continuing to push and ask questions and find new ways to do research," said Charles Littnan, lead scientist with the U.S. National Oceanic and Atmospheric Administration's Hawaiian monk seal research program in Honolulu.

Bad News for Monk Seals

However, the new study is bad news for the rapidly dwindling Hawaiian and Mediterranean monk seals, added Littnan, who was not part of the new research.

Conservationists trying to preserve both seal species used to say that if one of the species went extinct, at least there'd be a "backup" in their sister species.

"It's a little bit scary to suddenly [realize] these animals are even more rare than we thought," said Littnan. Now that "they're both the last of their own distinct lineages, it makes their uniqueness and their value all the greater."

On top of everything else, "living in the tropics is a tough way to be a seal," said Littnan—in fact, the majority of seal species live in more temperate areas and toward the Poles. (Related: "How a Leopard Seal Fed Me Penguins.")

Because monk seals tend to live where people do, they have additional challenges, whether it's sewage runoff, habitat destruction, conflicts with human fishing, or other factors.

"Monk seals may be teetering on the edge at the best of times, so anything extra can push them over," Littnan said.

A good example is the Caribbean seal, which may have once numbered as many as 338,000. Hunters in the Caribbean quickly wiped the docile animal off the planet in the 20th century, despite scientists regularly sounding alarms about its demise, Helgen said.

That it happened so fast "is very sobering," he said. "It reminds us how easy it would be to lose either [of the remaining] species."

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