The zoo’s staff rushed to aid the 270-pound tiger after her fall, but Mila ultimately succumbed to her injuries.

“You can plan and plan and things still go wrong,” Bob Chastain, the president and chief executive of Cheyenne Mountain Zoo, said Tuesday in a news release. “Our team delivered exactly the right amount of drugs to a very calm tiger who had trained for this moment. We have successfully anesthetized countless tigers in this same den, and have never experienced an accident like this. We never take decisions to anesthetize an animal for a procedure lightly, and this is a tragic example of why.”

Chastain said that before Mila slipped, she was on “a mission to save her own species” — or increase the number of Amur tigers, an endangered population that lives primarily in the harsher climate of eastern Russia’s birch forests, as well as China and North Korea. As few as 500 of the animals, also known as Siberian tigers, are left in the wild, John Goodrich, chief scientist for Panthera, the global wild cat conservation organization, told The Washington Post.

This goat was supposed to be a Siberian tiger’s dinner. Now they are best friends, and it is charming Russia.

Russia’s efforts to protect Amur tigers have helped slow the decline of a subspecies that was on the brink of extinction in the 1940s, but poaching, illegal trade and habitat loss continue to threaten an animal population that is key to keeping ecosystems in balance, Goodrich said. Plus, because of the Russian invasion of Ukraine, many of the international organizations working to conserve the tigers have pulled back, he said.

Mila — pronounced Mee-la — was born at the Toronto Zoo in 2021. After a 104-day pregnancy, her mother, Mazyria, gave birth to her and two other cubs that April — the first litter born at the zoo since 2007.

Weeks later, her siblings had to be euthanized because of organ defects. But Mila, the amber-eyed, rambunctious cub, thrived and captured hearts in Canada while chomping on steak, playfully nipping on her mother’s tail and sashaying around her enclosure.

In March, she was sent to Colorado Springs to one day breed with the zoo’s male tiger, Chewy. However, the two never began their courtship.

Throughout the five months Mila was at the Cheyenne Mountain Zoo, the tiger was “making such great progress,” said Rebecca Zwicker, an animal-care manager in the zoo’s Asian Highlands.

“She was a feisty and intelligent tiger, and the team had been patiently and consistently training with her to help her settle in and feel comfortable in indoor and outdoor spaces behind the scenes,” Zwicker said in a news release. “She was getting so close to being out where guests could see her. We were excited to introduce her to our community and for people to fall in love with her here, just as they had in Toronto.”

But her introduction to guests was delayed by a “severe dental issue,” according to the zoo — one that left untreated could become a fatal infection spreading through Mila’s sinuses. She needed surgery, so Mila’s caretakers began an injection-training process.

At the National Zoo, a dentist had a tiger by the tooth

When Mila voluntarily received her initial dose of anesthesia on Friday, the big cat jumped onto a bench to lay down as the drugs started taking effect.

Less than a minute later, though, she slipped. It happened so quickly that staff members were unable to stop her fall, zoo officials said.

“She could have slid off from that height a hundred times and landed in a variety of other positions and been unaffected,” said Eric Klaphake, Cheyenne Mountain Zoo’s head veterinarian. “The team quickly entered her den when it was safe and diligently tried for 40 minutes to give her lifesaving care.”

The news quickly rippled from Colorado to Mila’s former zoo in Canada, where staff members said they were “deeply saddened” by the death of a tiger with a “playful and endearing nature [that] touched many lives.”

The Toronto Zoo set up a memorial fund in Mila’s honor to help Amur tigers in the wild after a “tremendous outpouring” from the community, Amy Naylor, a zoo spokesperson, wrote in an email. The zoo will also display a banner near the Amur tiger habitat where visitors can share their memories of Mila.

“We hope her memory will help to inspire those who loved her, and animal lovers as a whole, to continue to fight for a world where wildlife and wild spaces thrive,” Naylor added.

Goodrich, the tiger biologist, echoed that sentiment.

“Tigers are one of the most charismatic and most loved and appreciated animals on this planet,” he said. “The fact that they’re so loved throughout the world and are in danger is mind boggling. People need to appreciate and understand that tigers need everything we can give them to protect them. Because if we lose tigers what hope do we have of protecting anything else?”