Scientists are learning more and more about elephant intelligence.

A new study, released online Monday in the Proceedings of the National Academy of Sciences, shows elephants are more perceptive than previously believed.

Researchers at the Bronx Zoo in New York City found that elephants can recognize themselves in a mirror, suggesting that they possess a degree of self-awareness that was, until now, credited only to humans, apes and dolphins.

They are among a handful of species to use tools, says scientist Joyce Poole, a renowned elephant expert who has studied the animals at Amboseli National Park in Kenya for more than 30 years. Captive elephants have piled tires into step stools to reach high branches. Elephants even have used logs to short out electric fences. Elephants communicate through a variety of calls -- some of which are inaudible to humans -- and chemical signals, Poole says. Elephants have been known to mimic the calls of other elephants, as well as the sounds of machinery and their keepers' voices.

They also have sophisticated societies, typically led by an older matriarch. Daughters stay with their mothers their entire lives and typically serve as babysitters for younger siblings, Poole says. Researchers have observed them trying to help sick elephants get back on their feet, she says.

Like humans, elephants even appear to experience emotional trauma -- such as the massacre of parents by poachers or others, says psychologist Gay Bradshaw at Pacifica Graduate Institute in Santa Barbara, Calif. In a paper in Nature last year, Bradshaw wrote that elephants display the symptoms of post-traumatic stress disorder.

And while some trauma victims never fully recover, with the right care and support, some elephants are able to heal, Bradshaw says. "Elephants have a capacity to forgive, to reach out even to humans who have been the source of a lot of their pain," she says. "It's our own prejudice not to see it."

Elephants Anna and Dolly of the Maryland Zoo in Baltimore soon will enjoy a new outdoor walking track and three additional companions. And here at the National Zoo, Kandula, Shanthi and Ambika will have four times as much room in their habitat as in their current exhibit, which is less than 1 acre.

More than half of the 78 zoos that exhibit elephants plan to construct bigger homes, says Kris Vehrs, executive director of the American Zoo and Aquarium Association. The renovations are driven by a growing respect for elephants, among the best-loved of all zoo creatures.

Yet a widening circle of critics now question whether elephants belong in zoos at all.

Groups such as the Humane Society of the United States say elephants — with their large brains and sophisticated social groups — suffer physically and emotionally from confinement.

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"The traditional zoos we see now and even the ones they are planning cannot exhibit elephants humanely," says Joyce Poole, a renowned scientist who for three decades has studied elephants in Kenya's Amboseli National Park. Captive elephants who live on concrete also are prone to arthritis and foot lesions that researchers don't see in wild populations, Poole says.

Huge animals need space

Since 2000, eight zoos have stopped displaying elephants or have announced plans to phase out their exhibits, according to the zoo association. The Detroit and San Francisco zoos sent their elephants to sanctuaries after concluding that their facilities couldn't meet the animals' needs. Others, such as Chicago's Lincoln Park Zoo, opted not to replace elephants that died.

Elephants also need more room than urban zoos can provide, says Marc Bekoff, a biology professor at the University of Colorado-Boulder who studies animal behavior. He says city zoos typically house elephants in small spaces with one or two companions.

The zoo association has high standards and has raised them twice in the past five years, Vehrs says. It discourages facilities from exhibiting lone elephants and has minimum space requirements.

Zoos also are working hard to prevent problems such as arthritis, says John Lehnhardt, vice chair of the association's steering committee for elephants. Many are replacing hard floors with sand or dirt, which may be easier on elephant feet.

"Historically, some facilities weren't as good," Lehnhardt says. "We're doing a better job today, and we're going to do a better job tomorrow."

Zoos also play central roles in education and conservation, says National Zoo director John Berry. By allowing visitors to experience wild animals up close, zoos encourage people to care about endangered species, Berry says.

According to the World Wildlife Fund, 300,000 to 600,000 African elephants are left in the wild, along with only 35,000 to 50,000 Asian elephants. "Asian elephants are heading for the cliff and could well be extinct within our lifetime," Berry says.

The National Zoo plans to spend $30 million on the first phase of its new Asian elephant habitat, Berry says. The zoo hopes to eventually breed a herd of six to 10 elephants. "It's a stunning display of our commitment to elephants," says Tony Barthel, National Zoo elephant curator.

A new way to see elephants

Les Schobert, former curator at the Los Angeles Zoo and North Carolina Zoo, dismissed such renovations as "baby steps." Schobert, a consultant for In Defense of Animals, says zoos could make better use of their money by investing in conservation and sending their elephants to sanctuaries in California or Tennessee where elephants can roam more than 2,700 acres.

Those sanctuaries may not be able to accommodate all 300 elephants now living in zoos. And neither sanctuary allows visitors. But these spacious refuges can still serve as a model for a new way to keep elephants, Schobert says.

Instead of housing a couple of lonely elephants in small urban zoos, Richard Farinato of the Humane Society says zoos should work together to build regional parks big enough to accommodate dozens of elephants. Schobert predicts animal lovers would be willing to travel to see elephants, just as families travel to Disneyland.

Some zoo directors are skeptical.

"It's a bit far-fetched," says Barbara Baker, president and chief executive officer of the Pittsburgh Zoo. "It's very difficult for zoos to fund-raise and support animals that aren't in their own facility."

Emptying the elephant houses also would deprive many people of the chance of seeing elephants, Vehrs says. That could reduce the public's enthusiasm for protecting elephants in the wild.

But Farinato says, "It's all in the way it's marketed. We've been singing one song to the public: that you need to have live animals to look at so you can love them. But if we tell them that elephants need to be pooled together so they can be healthy, they will believe that."