With elephants and rhinos getting all the attention with their dwindling numbers, Africa's other iconic animal, the giraffe, is going unnoticed. Giraffe numbers have dropped 40 percent in the last 15 years, a fact that has flown under the radar until now.

"It's a silent extinction," Dr. Julian Fennessy, a wildlife expert conducting the first comprehensive assessment on giraffes, told ABC News. "The numbers have gone down from 140,000 to fewer than 80,000 today," he added.

As the world's tallest mammals, standing at up to 19 feet tall, giraffes (Giraffa camelopardalis) are well recognized animals. But their towering physique also most likely makes them easy to spot by poachers, who are contributing to their declining population, along with habitat loss and fragmentation.

According to the African Wildlife Foundation, the encroaching human population is pushing giraffes out of their native forests and open plains, due to agriculture and construction of roads. Not to mention that giraffe tails are prized among many African cultures, used to make good-luck bracelets, fly whisks, and thread for sewing.

Astonishingly, a 2010 report for the Rothschild Giraffe Project noted how some people in Tanzania believe giraffe meat to be a cure for HIV.

"It is believed [in Tanzania] that giraffe brains and bone marrow can cure HIV-AIDS victims," researcher Zoe Muller wrote.

"In rural African communities, bush meat not only forms a large part of the diet but also provides an important source of income," he said, adding, "Killing a giraffe involves relatively little effort for the amount of meat yielded as a large quarry can be secured with a single gun-shot."

The heads or bones of these beautiful creatures are worth up to $140 per piece.

So poachers scour the 21 countries in which giraffes reside, targeting them whether it's in state-owned national parks, private or communal lands. As a result, fewer than 300 West African giraffes survive in Niger and less than 700 Rothschild's giraffes can be found in Uganda and Kenya, ABC reports.

And while many might be misguided in believing that these spotted animals are abundant, Fennessy hopes that his latest assessment, to be published next year, will open people's eyes.

"Giraffes haven't hit the headlights yet," he said. "They're not on many NGOs agenda, but hopefully that is changing."

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