Social media has played a huge role in publicizing the issue, with more than 100,000 users following the lead of Ms. Nyong’o, Yoko Ono and other celebrities who signed onto WildAid’s #JoinTheHerd campaign. In the spirit of Facebook’s popular rainbow filter to show support for same-sex marriage, users can upload split-screen photos of their faces with an elephant face as their profile photo.
To combat demand for ivory in Asia, the group has also enlisted the likes of Yao Ming (the Chinese-born former Houston Rockets star), Li Bingbing (a prominent actress in China) and Maggie Q (an actress who starred in the CW assassin drama “Nikita” and CBS’s “Stalker” and whose mother is Vietnamese).
“It basically takes an army of 30 people to protect one elephant,” said Maggie Q, who began her acting career in Asia. “On the other hand, what is most effective is to speak to consumers. And there’s an entire side of the world that knows me, knows my values and knows my face.”
Many celebrities go beyond supplying a pretty picture and a quote.
Last summer, Jared Leto, an ambassador for the World Wildlife Fund, co-wrote an editorial in Time magazine demanding that the United States do more to stop the slaughter. “Our collective efforts don’t match the scale and speed of the calamity before us,” he said.
A number of Hollywood notables have also trained their cameras on the cause, making documentaries about the plight of the elephants: Kathryn Bigelow, the Oscar-winning director (the short film “Last Days”); Kristin Davis of “Sex and the City” (who produced and self-financed “Gardeners of Eden”); and Paul Allen, the Microsoft co-founder and Hollywood producer. (He produced “Naledi: A Baby Elephant’s Tale,” which will debut next month at the Seattle International Film Festival.)
The celebrity efforts provide another crucial weapon for conservationists: money.
While philanthropic associations do not track donations to elephant causes specifically, fund-raising for wildlife in general (including other much-publicized endangered animals like rhinos and tigers), appears to be on the rise, according to the Giving USA Foundation.
In 2014, donations to animal and environmental causes rose to $10.5 billion, up 43 percent since 2009.
At a grass-roots level, a celebrity-fueled social media campaign like #JointheHerd can persuade the masses to reach for the credit card, said Mr. Harmon of WildAid. Since the campaign began in February, WildAid has seen the number of small donors to its elephant initiative rise 94 percent, he said.
Celebrities also persuade other celebrities to open their wallets.
Last fall, for example, Owen Wilson hosted the Elephants Forever Auction at Sotheby’s, featuring artwork by Tom Sachs and Rob Pruitt, among others, that drew the likes of Waris Ahluwalia, the actor and jewelry designer, and Ms. Sarandon and raised more than $1 million for Elephant Family, benefiting Asian elephants, and Space for Giants.
“Maybe it sounds corny, but there’s sort of a wisdom to elephants,” InStyle quoted Mr. Wilson as saying.
Elephant Family will make further inroads into the art world this summer, when it takes the Elephant Parade, a showcase of elephant-themed outdoor art by David Yarrow, David LaChapelle, and other artists, to the Hamptons
Similarly, the fashion industry has gotten involved. Two years ago during MADE Fashion Week the Clinton Foundation headed a campaign to install a 10-foot pink elephant, designed by the artist Tristin Lowe, at Milk Studios to raise awareness for its #SaveElephants campaign. (The concept reportedly grew out of conversations among Chelsea Clinton, Diane Von Furstenberg and Oscar de la Renta, all elephant champions).
At Vancouver Fashion Week in February, a group called Elephanatics enlisted 13 designers to conjure elephant-inspired couture clothing “to reach out to a crowd that is more or less responsible for the plight of elephants — people in fashion,” said Ava J. Holmes, who produced the show. J. Crew has been selling a “Save the Elephants” T-shirt for charity, featuring an illustration by the artist Hugo Guinness.
Certainly, it will take more than art auctions and fashion shows to overcome this global crisis. Like the drug trade, the illicit ivory trade involves vast criminal syndicates and countless corrupt government officials, said Trevor Neilson, the president of Global Philanthropy Group in Los Angeles.
“If you want to understand the issue, you have to talk former C.I.A. officers who are in touch with Kenyan intelligence who can tell you who is corrupt at the port at Mombasa,” Mr. Neilson said.
By contrast, “When a well-meaning reality TV star in Los Angeles is tweeting ‘save the elephants,’ I think it’s safe to say that that has no impact whatsoever,” he said.
Even so, there are reasons for hope, conservationists say. On a visit to the United States in September, President Xi Jinping of China promised to enact “nearly complete” bans on ivory import and export.
In the United States, four states including California and New York have enacted ivory restrictions, with others pending. (Citing “horrific cruelty,” Meryl Streep joined the Humane Society’s fight in her home state of New Jersey. Woody Harrelson told representatives in Hawaii that “the world is watching.”)
President Obama has called for a near-total ban on the ivory trade in the United States, and conservation groups expect the new law to be put in effect this summer.
Meanwhile, in a related issue, Ringling Bros. and Barnum & Bailey agreed to retire its touring circus elephants this month, after years of strident opposition from stars like Alec Baldwin, working with People for the Ethical Treatment of Animals.
Such progress is enough to keep celebrities like Ms. Davis going. And going. And going. In recent years, the erstwhile Charlotte has made elephants a mission, taking some 15 trips to Africa, helping serve the David Sheldrick Wildlife Trust, which rescues baby elephants orphaned by poaching, and releasing the unflinching documentary “Gardeners of Eden” in 2014.
She finds the issue gripping in part because elephants seem so human in their behavior, she said: Each herd has its matriarchs, its wise old aunts, its rowdy teenagers. When an elephant dies, the others mourn. “They touch the body with their feet, smell it with their trunks, and stand around for a day or longer,” Ms. Davis said. “It’s almost like sitting shiva.”
And unfortunately, there is a lot of that going on in Africa these days, she said. “How on earth will we be able turn to our children and say, ‘All those elephants in books, they used to be everywhere, now they’re gone.’”
Because of an editing error, an earlier version of this article referred incorrectly to the mother of Maggie Q. She is not an actress who starred in “Nikita” and “Stalker.”