A sign outside Sandra's cage explains that "orangutan" comes from the Malay expression for "person of the forest." But she remains in a concrete cell in a Buenos Aires zoo and may never see the rainforests of her ancestors.

Sandra's release seemed imminent after an Argentine court said in 2014 that she was entitled to some legal rights enjoyed by humans in a landmark ruling. It seemed even nearer when the 140-year-old zoo where Sandra has lived for most of her life closed its doors this year and officials announced that hundreds of its animals would be set free.

But now the judge who fought to free the 32-year-old orangutan is agreeing with her caretakers that it might be best just to improve the conditions of her cage instead of sending her to a reserve abroad, because such a move would put her life at risk.

"We don't have any options here ... we're facing a certain reality," said Judge Elena Liberatori. "Sandra has a millstone hung around her neck."

A panel of three international experts reviewed Sandra's situation and presented a set of recommendations to Liberatori last year. The options included: releasing Sandra into the wild, transferring her to a sanctuary, or "constructing an accommodation" for the ape. But all the choices have negative aspects.

Sandra was born in a zoo in Germany and is an institutionalized orangutan, so the panel recommended against releasing her into the wild fearing she would not survive. It also said that since Sandra is classed genetically as a hybrid orangutan — half Sumatran, half Bornean — she might not be able to adapt if sent to Indonesia, where most of the world's wild orangutans live and there are a number of sanctuaries. Suitable facilities might be found abroad but they would need to be reviewed carefully.

For now, everyone from her caretakers to the judge and lawyers agrees with the experts that while she is in captivity, Sandra's accommodations, medical treatment and care must be improved.

"Ultimately, it is a question of our humanity how we treat Sandra. We know that orangutans are intelligent beings who care for their children and can learn about the world in which they live," said Shawn Thompson, a member of the panel and the author of "The Intimate Ape: Orangutans and the Secret Life of a Vanishing Species."

An Argentine court sided with Sandra after a local rights group filed a habeas corpus writ on the orangutan's behalf. It said that "a great ape has rights, including freedom and avoiding suffering from being in captivity."

Last year, Liberatori went further and ruled that Sandra is legally not an animal but a "non-human person." Then in June, another court said Sandra is "a sentient being." It also said the former zoo, now an eco-park managed by the government of the city of Buenos Aires, must improve Sandra's well-being while experts determine her future.

The former Palermo zoo was inaugurated in 1875 on what was then the outskirts of Buenos Aires but is now encircled by noisy neighborhoods, with honking buses passing a few yards from some cages.

Many of the enclosures are considered inhumane by modern standards. Sandra's is a basketball court-sized concrete space with iron bars that resemble those in a prison. She is the only member of her species in the zoo.

"There's a global trend that has turned the social role of zoos from places where you keep exotic animals into places that play a role in the conservation of biodiversity," said Rosario Espina, director of biodiversity at the Buenos Aires eco-park.

Espina said the park is looking into the possibility of a private sanctuary on the outskirts of Sao Paulo, Brazil, but that will depend on the conditions there and Sandra's health.

"At this point, I think Sandra will stay here, but if there's a possibility that her conditions can improve somewhere else we will, of course, encourage a transfer," she said.

Blood tests and X-rays show Sandra is in normal health, said Guillermo Wiemayer, the eco-park's veterinarian. Orangutans can live to 50 years in captivity depending on the conditions.

But Wiemayer said that in order to determine whether she can travel safely, more tests would have to be carried out and she might need to be sedated, posing a health risk. Others risks include the trauma, mental and emotional distress caused by a transfer.

Inside her cage, Sandra covers her head with a piece of cardboard or a cloth. She picks up seeds scattered on the floor or straws dangling from her ginger hair. She often stares at visitors from behind the bars.

Her enclosure has been improved since the court decisions, but Sandra needs more space. Liberatori, who is in charge of overseeing the process, got a ferry company to donate ropes for the orangutan.

"Her natural habitat is missing, and I think she'll never have it," Liberatori said. "I wish she had soil, grass, plants. They have a tree now. It was one of the improvements, but it's just some wood, not a real tree."

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Associated Press video journalist Paul Byrne contributed to this report.