120 miles of Russian forest couldn't keep these two tigers apart

When Russian scientists released a pair of orphaned Amur tiger cubs into the wild in a remote corner of Russia's far east in 2014, they were trying to save a species. While the tigers, sometimes called Siberian tigers and the world's largest big cats, remain endangered, the scientists created something else: an unlikely love story.

The cubs, Boris and Svetlaya, had been rescued from the wild as unrelated 3- to 5-month-old cubs in the Sikhote-Alin mountains, the animals' main stronghold. They grew up in captivity and were released at 18 months old. The cats were separated by more than 100 miles with the goal of expanding the distribution of released tigers as much as possible in the Pri-Amur region along Russia's border with China.

The scientists tracked the cubs until, more than a year after their release, something strange happened: Boris walked more than 120 miles, almost in a straight line, to where Svetlaya had made a home.

Six months later, Svetlaya gave birth to a litter of cubs.

While the strategy of releasing rescued cats raised in captivity to restore populations in the wild had proved successful with the Iberian lynx in Spain, it had never been tried with big cats.

But scientists working with the Wildlife Conservation Society say in a study published last month in the Journal of Wildlife Management that the successful release of rescued cubs like Boris and Svetlaya may, for the first time, become a viable option for restoring wild tigers to their historical range.

Estimates of the number of tigers left in Russia range from 485 to 750. But researchers say that the Russia-China border area, including the Pri-Amur area where Boris and Svetlaya live, could support hundreds more of the animals.

The reunited cats were not the project's only successful reintroductions. Two hunters had found another female, Zolushka (or "Cinderella" in Russian), in a snow drift a few years earlier. After the conservationists returned her to the wild, an unknown male tiger showed up on a camera trap near where Zolushka had been released.

In such a vast area, it was an encounter of extraordinary good fortune. "Cinderella's prince showed up and they lived happily ever after," said Dale Miquelle, lead tiger scientist for the Wildlife Conservation Society and an author of the study. Zolushka and the male also produced a litter of cubs, the first known cubs to be born in that area since the 1970s.

In all, Russian scientists raised 13 orphaned Siberian tiger cubs in captivity, avoiding any contact between the growing cubs and their human caretakers so as to prepare them for life in the wild. The team gradually introduced the cubs to live prey, so that they could learn how to hunt.

Also critical to the success was the timing of the cubs' release: during spring when prey was plentiful.

One male cub failed the test of freedom. He wandered into China and preyed on domestic animals, including 13 goats in one shed in a single night. Russian scientists recaptured the young male and sent him to a captive-breeding program at a zoo.

But the remaining 12 proved that they were able to hunt wild prey and to survive as well as wild tigers that had never spent time in captivity.

As the Pri-Amur population grows, the Russian-American team hopes that it can join up with other tigers, including across the border in China. "The grand vision is that this whole area would be connected," said Luke Hunter, executive director of the Big Cats Program at the Wildlife Conservation Society. "There's lots of habitat that could be recolonized by tigers."

With so much potential habitat across Asia -- a 2023 study found that there was around 270,000 square miles of potentially suitable habitat across Asia where tigers remained absent -- the implications of this success are wide-ranging.

"These results indicate that it is possible to care for young cubs in a semi-captive environment, teach them how to hunt and to release them back into the wild," said Viatcheslav V. Rozhnov, former director of the Severtsov Institute of Ecology and Evolution of the Russian Academy of Sciences and leader of the reintroduction project. "These findings provide a pathway for returning tigers to large parts of Asia where habitat still exists but where tigers have been lost."

And just as Boris and Svetlaya's unlikely partnership has proved critical to the project's success, the Russian and American scientists hope their efforts may be a model for international conservation cooperation.

"It's a testimony to how really good things can happen when you start working collaboratively irrespective of nationality and politics," Miquelle said.