Wolves, they add, are seven times more populous than animals in those radiation-free areas.
"It's very likely that wildlife numbers at Chernobyl are much higher than they were before the accident," said Jim Smith, of the University of Portsmouth, in a press release.
While earlier studies had shown sharp drops in wildlife thanks to radiation effects, the new data, culled from long-term census information and helicopter surveys, argues that mammals are back with a vengeance.
"These results demonstrate for the first time that, regardless of potential radiation effects on individual animals, the Chernobyl Exclusion Zone supports an abundant mammal community after nearly three decades of chronic radiation exposure," the scientists wrote.
"This doesn't mean radiation is good for wildlife," Smith cautioned, "just that the effects of human habitation, including hunting, farming, and forestry, are a lot worse."
The team's findings have been published in the journal Current Biology.