A critically endangered Amur tiger - one of only 500 - died on Friday in a "freak accident" as a Colorado zoo tried to operate her for a "severe dental issue".

Mila, who was moved to the Cheyenne Mountain Zoo (CMZoo) in Colorado Springs from Toronto Zoo in March 2023, was suffering from a dental issue, which needed to be operated on, said CMZoo in a statement.

"This was not just a cavity; and it could not be left untreated, as it was advancing to her sinuses. Left untreated, infections like this can be fatal for animals," said the zoo.

The issue was also delaying Mila's introduction to the CMZoo community.

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How did Mila die?

CMZoo's team had been working on integrating Mila in her new surroundings and helping her getting used to moving around comfortably on her own when they realized that she needed surgery to treat her dental issue. They prioritized re-establishing a voluntary injection training that the Toronto Zoo Wildlife Care staff had previously established.

As a result of this training, Mila voluntarily received the injection of initial anesthesia on Friday and then jumped up on a bench where she began to lay down and let the anesthetic drugs take effect. However, in an unfortunate turn of events, less than a minute after lying down, she slipped off of the waist-high bench, and fell resulting in a fatal spinal injury.

"Given the short timeframe from her lying down to her slipping off, it was impossible from a human safety standpoint to stop her tragic fall," the zoo said in their statement.

“She could have slid off from that height a hundred times and landed in a variety of other positions and been unaffected,” said Dr. Eric Klaphake, CMZoo head veterinarian. Dr. Klaphake said that the team quickly responded to the incident, entering her den when it was safe and tried giving the tiger life-saving care for 40 minutes. However, she could not survive.

“These are impossible life-and-death decisions being made in real time,” said CMZ Zoo president and CEO Bob Chastain. “You can plan and plan and things still go wrong."

Chastain said that the zoo's team delivered the "right amount of drugs to a very calm tiger who had trained for this moment," adding that countless tigers have been successfully anesthetized in this same den in the past.

"We never take decisions to anesthetize an animal for a procedure lightly, and this is a tragic example of why,” said Chastain.

Why was Mila moved to CMZoo?

Pronounced “Mee-la”, meaning dear one, Mila was the only survivor of her mother Mazyria's three-cub litter. She was moved from Toronto Zoo to CMZoo earlier this year, a little after she turned 2. CMZoo said that tigers generally disassociate from their parents at that age to live their own solitary lives and that Mila and her mother Mazy were showing signs that they wanted their own space.

Mila was brought to the CMZoo on a future breeding recommendation. However, she never got the chance to meet CMZoo's male tiger Chewy.

“She was making such great progress with us,” said Rebecca Zwicker, animal care manager in Asian Highlands at CMZoo. “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 that Mila was close to being out to where guests could see her, and that the zoo was excited to introduce her to their community and "for people to fall in love with her here".

Mila is the second female Amur tiger to pass away at CMZoo in recent years. In 2021, Savelii passed away due to complications during recovery from an artificial insemination procedure. After Savelii's death CMZoo made a long-term financial decision to support tigers in their natural habitat as well as in the Zoo.

The two deaths are unrelated, but the zoo said the incident illustrates how the “fragile state of their species is glaring.”

Both zoos also requested visitors to respect the grieving wildlife care staff and refrain from approaching them with questions about Mila "to give them the time and space they need to process this heartbreaking news".

Mila Memorial Fund

The Toronto Zoo has set up a memorial fund in Mila’s honor to help Amur tigers in the wild after a “tremendous outpouring” from the community while CMZoo said that they are committed to preventing such "freak accidents" in the future.

"Many of you have indicated you would like to bring flowers to the Zoo, [so] we are encouraging people to make a donation in her honor," said the Toronto Zoo. "Her playful and endearing nature touched many lives, and inspired people to fight for the survival of this endangered species in the wild."

The fund established through the Toronto Zoo Wildlife Conservancy Wilding Fund will support endangered species conservation projects in the wild.

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Critically endangered

Native to the Sikhote-Alin range in Russia's Far East and small pockets in the border areas of China, Amur tigers are critically endangered in the wild with only around 500 individual tigers roaming their native habitats. Amur tigers live up to 10-15 years in the wild and up to 20 years in captivity.

About a 100 are known to be in human care, at zoos and aquariums accredited by the Association of Zoos and Aquariums (AZA) in the U.S. and Canada, according to CMZoo.

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