WASHINGTON — The sound was like nothing Tom Hinton had ever heard before: a chorus of baleful wolf howls, long and loud and coming from seemingly every direction in the darkness. The predators yipped and chirped and crooned to one another for what seemed like forever, sending a shiver of awe and intuitive fear down Hinton’s spine.
‘‘It was a primordial experience,’’ he said, something most of humanity hasn’t felt for tens of thousands of years, ‘‘back to when humans were prey.’’
It was only possible because of where Hinton was standing, a remote area along the Belarus-Ukraine border uninhabited by humans for decades.
They all left in the wake of a very different sound: the massive explosion of the Chernobyl Nuclear Power Plant in 1986 that left dozens dead and that spread a cloud of radiation driving more than 100,000 people from their homes across a 1,600-square-mile swath of Ukraine and Belarus.
These days, abandoned apartment complexes are crumbled concrete wrecks. Vines crawl up the decaying walls of old farmhouses and break unintended skylights into their roofs. No one lives in the post-apocalyptic setting.
No one human, that is. Wildlife populations there — shaggy-haired wild boar, long-legged elk, the choruses of wolves that so captivated Hinton in August — are flourishing.
That’s according to a study published recently in the journal Current Biology, which found that mammal numbers in the radiation-tainted exclusion zone are as high, if not higher, than in even the most protected parks in Belarus.
‘‘That wildlife started increasing when humans abandoned the area in 1986 is not earth-shattering news,’’ Hinton, a radioecology expert at Fukushima University in Japan and coauthor on the paper, said. ‘‘What’s surprising here was the life was able to increase even in an area that is among the most radioactively contaminated in the world.’’
In other words, whatever the fallout from the disaster may have been for wildlife, the absence of humans was more than enough to compensate.
The study by Hinton and Jim Smith, an environmental science professor at the University of Portsmouth in England, is the first real census of wild animals in the exclusion zone. It relies on a decade’s worth of helicopter observations in the years right after the disaster, and three winters of scientists carefully counting animal tracks on foot from 2008 to 2010 in the Belarusian section.
Though animal numbers were low when scientists first started counting them in 1987 (because no data was taken before the disaster, they can’t tell to what degree the populations were hurt by the explosion), they rapidly rose once humans left the region.
Brown bears and rare European lynx — predatory cats the size of a Great Dane — quickly appeared in the forests, even though they hadn’t been seen for decades before the accident. Wild boar moved into abandoned buildings.
Within 10 years, every animal population in the exclusion zone had at least doubled. At the same time, species flourishing in the exclusion zone were vanishing from other parts of the former Soviet Union, likely due to increased hunting, poorer wildlife management, and other economic changes.
By 2010, the last year of the on-foot census, the populations for most species were as large as in any of the four national parks in Belarus. For one species, the wolves, the population was seven times bigger.
The presence of wolves is particularly telling. As apex predators, they are a sign of the health of the entire ecosystem. This indicates to researchers that chronic exposure to radiation has had no impact on overall mammal populations.
This doesn’t mean that the zone isn’t dangerous, Hinton stressed. He and his colleagues didn’t study the individual- and molecular-level damage caused by lingering contamination. While whole populations aren’t dying out, individual animals might be getting sick. And the soil in areas close to the reactor site still exudes radiation.
But, Hinton said, ‘‘the environment is very resilient.’’
For Hinton, who is currently studying the effects of the 2011 Fukushima nuclear disaster, the impact is both astounding and sobering.
‘‘It’s an amazing experience from a wildlife perspective, but it’s also a sad experience because you see homes that have been abandoned and you imagine the people’s lives that have been disturbed,’’ he said. ‘‘It’s sad to see the houses and the cars and the baseball bats and you envision the life that people had to drop and leave. But you also see wild boar running around and you don’t see that as soon as you leave the zone.’’