A week-old calf at Artis Zoo in Amsterdam, the Netherlands, in November. (Koen Van Weel/EPA)

The stately 18-foot-tall giraffe is among the animals ecologists call “charismatic megafauna,” the name for critters that elicit squeals of delight at the zoo and warm the cockles of corporate marketers. Of the most charming beasts, though, giraffes never managed to generate attention on par with rhinoceroses — a subspecies of which is poised to vanish — or elephants, facing a long and bitter history of ivory poaching.

Researchers were not immune to passing over the giraffe, either. In September, Axel Janke, a German evolutionary biologist, laid it out to National Geographic like this: “Only 400 scientific papers have been written about giraffes, versus 20,000 papers on white rhinos.” The animal was so understudied that just how many species of giraffe exist is a matter of some debate.

But it was agreed, during a meeting of the International Union for the Conservation of Nature on Wednesday, that the tallest species on the planet is rarer than previously understood.

“There is a silent extinction going on,” Julian Fennessy, an IUCN giraffe specialist and director of the Giraffe Conservation Foundation, told The Washington Post by phone early Thursday.

The IUCN, an international NGO headquartered in Switzerland, manages guidelines called the Red List. The Red List is designed to help nations conserve threatened species. If sufficient information exists about the animals, the list classifies creatures on a scale from least concern to extinct. As recently as 2010, the IUCN listed the giraffe as species of least concern.

On Wednesday, the IUCN downgraded the giraffe from least concern, skipped “near threatened” and classified the animal as vulnerable. The giraffe shares this status with the cheetah, the leatherback sea turtle and other species. Giraffes are now considered by the IUCN to be as threatened as African elephants, though the giraffe population is a quarter of its pachyderm neighbors.

“One of the world’s most recognizable animals and the tallest land mammal,” wrote the IUCN in a statement released Thursday, “is now threatened with extinction.”

Giraffes numbered between 151,000 and 163,000 animals, according to a 1985 estimate. A new assessment, per a IUCN giraffe specialist group formed four years ago, determined that the animals declined to 97,562 in 2015. That is, over the course of three giraffe generations, the population plummeted between 36 and 40 percent. Going back even further in history, Fennessy said, could paint an even grimmer picture; 200 years ago, it is possible there were as many as a million giraffes across Africa, he said.

The IUCN cited human population growth and poaching as factors for the decline. Habitat loss, too, played a role. A June 2015 study of Serengeti giraffes found their diet took a hit after woody, “unpalatable species” of trees grew up where the tastier acacia plants once grew. In areas disturbed by war and civil unrest, such as South Sudan, giraffe subspecies such as the Nubian giraffe have dropped by as much as 95 percent.

Fennessy and other conservationists hope the vulnerable status will bring needed attention to giraffes. “People see the animals on safari in Kruger National Park,” he said, referring to a well-managed wildlife reserve in South Africa, “and they assumed that giraffes are everywhere.” As the decline shows, that is not the case.

In addition to conservationists, biologists are also taking a closer look at the long-necked icon. Zookeepers knew the animals would let loose the occasional snort, but scientists only recently discovered that the creatures emit deep hums, on the low end of human hearing, after nightfall. Researchers are unspooling giraffe DNA to determine how it evolved to stand so tall.

There are in fact four different species of giraffe, not one, argued a genetic analysis published in September. The IUCN, on the other hand, recognizes only one species — Giraffa camelopardalis — with nine subspecies.

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