The Eurasian lynx vanished for nearly a century from most of Europe, but it has made a big comeback in the radioactive exclusion zone around the Chernobyl nuclear reactor in northern Ukraine. For years, the big cats with tufted ears left only occasional signs of their presence in the zone: tracks the size of wolves’ but without claw marks, scratches left on tree bark.

But camera trap videos have recently provided the most dramatic proof of the animals’ existence. Filmed in a highly radioactive forest a few miles west of the Chernobyl reactor complex, a female lynx with adolescent cubs display their pale yellow winter pelage as they amble in the snow. They were filmed near where an international conglomerate is building a new dome to cover the aging sarcophagus entombing the ruined reactor. Two more family groups were filmed within 12 miles of this location, suggesting healthy and growing populations.

The camera trap photography is the personal passion of biologist Sergey Gashchak. Over the winter, his cameras captured boars, elk, roe deer, wolves, moose, and most remarkably, lynx—many of them.

Once common, lynx were exterminated by the 20th century in Western Europe thanks to deforestation and hunters who considered them a threat to game and livestock. Considered a vulnerable species today, 90 percent of the world’s lynx live in the forests of Siberia, with small pockets from the Balkans to the Baltics. France and Switzerland have successfully reintroduced small populations, but most of Europe is simply too crowded to accommodate the lynx’s enormous range, which can be as high as 170 square miles, depending on the availability of prey.

The 1986 Chernobyl disaster led to the evacuation of more than 100,000 people, and abandoned Soviet collective farms reverted to the region’s natural forests and swamps. Afterwards, all large European mammals have found the zone to be an inviting habitat. It is Chernobyl’s enduring paradox that the absence of people has made the land safe for wild animals, despite radiation, with species diversity and abundance far greater within the zone’s fenced borders than outside them. Its vast, wild expanses are especially inviting for lynx.

The first lynx sightings around Chernobyl began at the end of the 1990s, when Ukrainian biologists estimated that about a dozen animals might live on either side of the Belarus-Ukraine border that cuts the exclusion zone into two approximately equal halves. Given the variety of prey, and especially roe deer—their calves are a lynx favorite—biologists expected the Chernobyl populations to grow. Fifteen years later, as many as several hundred lynx might be roaming the Rhode Island-size zone. But no one knows their numbers for certain. The last animal census in the zone took place in Belarus in 2007. That report noted the presence of lynx but didn’t count them.

No one knows how radioactive Chernobyl’s lynx are, either. Since radioactive contamination concentrates up the food chain, lynx—like wolves, the zone’s other large predators—are probably accumulating radioactive cesium in their muscle and strontium in their bones. But that’s only a guess, too. After fugitive ex-president Viktor Yanukovich gutted Ukraine’s budget by as much as $70 billion during his four years of rule, no money was left for Chernobyl research.

But the lynx, like the zone’s other animals, don’t care if there’s money for research or not. The less we bother them, the better.