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 cat, 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 animal’s main stronghold. They grew up in captivity and were released at 18 months old. The cats were separated by more than 100 miles apart 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 over 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.