She hasn't seen another elephant for the past three years, and she's been in a zoo for over half a century.

Her name is Lucky.

Now 56 and the only elephant at the San Antonio Zoo, Lucky was taken from the wild as a baby back in the 1960s. She was shipped to the U.S., where she has lived in captivity ever since.

In 2013, Boo, Lucky's last companion, passed away. Even though it's against Association of Zoos and Aquariums (AZA) guidelines, for the past three years, Lucky has lived totally alone.

Elephants are generally highly social animals who, in the wild, live in herds of up to 100 other elephants.

"Our position is that by housing Lucky in solitude, for a species as social as elephants are, it's unequivocally harmful to her," Carney Anne Nasser, senior counsel at the Animal Legal Defense Fund (ALDF), told The Dodo. ALDF is currently pursuing a lawsuit on Lucky's behalf. "ALDF's goal is to ensure that Lucky gets to spend her last years at a sanctuary, in a more appropriate habitat with other elephants, where she can have a meaningful existence, and not just be a way of selling tickets."

Asian elephants in the wild usually roam great distances, foraging for food. When put in enclosures, elephants can exhibit what are known as "stereotypic behaviors," like swaying back and forth, that stem from the stress of captivity. Sadly, even wild elephants are struggling to find space to move: Habitat destruction is one of the biggest dangers to their survival.

Even though Asian elephants are no longer allowed to be caught in the wild and brought to live in U.S. zoos, and some zoos have already come to the conclusion that it's not possible to give zoo elephants the lives they deserve, the aging elephant's fate remains uncertain.

Recently, Lucky got a visit from someone from her past. Keith Hodges, who suffers from stage 4 lung cancer, used to work as a keeper for elephants at the zoo in the 1970s. He recently told his daughter how much he'd like to see Lucky again. So, she contacted the zoo to make her father's wish come true: to see the elephant he hasn't seen in 45 years.

Hodges and the other keepers who were working at the zoo decades ago can still remember when Lucky arrived. "She came in a crate," Raymond Figueroa, Hodges' old boss, recalled. "She was a baby."

On Monday, Hodges approached the elephant he'd once known. Lucky approached the fence separating them. She nudged him with her head. It's unclear whether she remembered him or whether she was just relieved to have contact with anyone at all.

The zoo recently invested in improving Lucky's habitat with a pool in which she can submerge herself. But many believe that for an animal as naturally social as Lucky, improving her enclosure is far from enough.

"It used to be when you waved at her she would put her trunk up," Hodges said.

The San Antonio Zoo did not reply to The Dodo's request for comment.

Click here to learn more about ALDF's work on behalf of Lucky.