The Dogs of Chernobyl Are Going Through Strange Genetic Changes

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The Dogs of Chernobyl Are Going Through Strange Genetic Changes. Scientists Are Still Trying to Figure Out Why.
These canines “survived for a reason,” an expert told us. But what exactly is causing these rapid genetic transformations?

Feb 19, 2025


On April 26, 1986, the world’s worst nuclear disaster unfolded at the Chernobyl Nuclear Power Plant in what is now northern Ukraine. After one of the plant’s reactors exploded during a test, it spewed uncontrolled, high-energy radiation, eventually contaminating about 58,000 square miles across Belarus, Russia, and Ukraine.

Soon after, to reduce the spread of radioactive elements from the accident, cleanup workers called “liquidators” were tasked with culling thousands of contaminated animals surrounding the plant. These included pet dogs left behind during evacuation.

Today in Chernobyl, the remaining levels of radiation vary across the landscape between amounts lower than natural background radiation—which is present in the environment around us, making up about half of our average yearly radiation exposure—to levels thousands of times higher.

Scientists are still debating how long-term radiation exposure may or may not be impacting the genomes of surviving creatures and their offspring in the Chernobyl Exclusion Zone, the sealed-off, Yosemite National Park-sized area surrounding the plant. After all, it’s tricky to nail down the relationship between radiation exposure and changes in different organisms.

Unlike the tidy conditions in a lab, real-life locales like the 19-mile radius Exclusion Zone come with all kinds of compounding factors.

It’s actually a cocktail of toxic, hazardous, carcinogenic chemicals, any one of which or combination thereof could lead to the kinds of changes that we’re seeing,” says Matthew Breen, a geneticist at North Carolina State University.

The free-breeding dogs that roam the Exclusion Zone, which may have descended from abandoned pets, could offer some clues about radiation exposure and genetic changes. In a 2023 study, scientists showed that dogs living in the Exclusion Zone are genetically distinct from nearby communities of dogs. But according to new research published in December 2024, which Breen collaborated on, those differences likely weren’t just a result of radiation, as some experts had suspected.

So if the dogs of Chernobyl aren’t experiencing rapid evolution due to the direct effects of radiation, what is causing it?

This kind of genetic detective work in disaster zones didn't focus on large mammals like dogs until fairly recently. Now, researchers like Breen are wielding high-tech, increasingly sensitive screening methods to find answers that weren’t previously possible.

In 2017, a team from the U.S. and Europe began collecting and analyzing genetic samples from free-roaming dogs in and around the Exclusion Zone. They found distinct genetic differences in the Exclusion Zone population compared with dogs living in nearby Eastern European countries, and even dogs living about 10 miles away in Chernobyl City, according to the 2023 paper.

In their 2024 work, Breen and his teammates looked for increased mutation rates on the chromosomal level and the genome level, and even zoomed into the dogs’ single nucleotides, the molecular building blocks of DNA. While the dogs are roughly 30 generations removed from the accident, these mutations would be passed on to present populations if they provided a survival advantage.

Ultimately, the search for higher rates of mutations spurred by radiation exposure came up empty.

But this research can go a step further: it’s crucial to determine whether the genetic changes seen in the Exclusion Zone dogs may affect survival and reproduction, says Christelle Adam-Guillermin, a senior researcher at France’s Nuclear Safety and Radiation Protection Authority. This would require linking the dogs’ genetic differences with potential changes in gene expression and functional responses (like changes in phenotypes). Breen says the team would need to take more blood samples in the Exclusion Zone, but his colleagues haven’t been able to do so since 2020 due to the ongoing Russo-Ukrainian War.

“If you want to go further and really understand the consequences of these changes, you would need to have responses at the level of genes, proteins, phenotypes to have a different weight of evidence,” says Adam-Guillermin.

Some species around Chernobyl seem to have fared differently. Scientists have found that increased rates of mutations in Daphnia, a type of tiny crustacean, and rodents called bank voles may be linked to chronic radiation exposure since the incident.

Research from Breen’s co-author, Timothy Mousseau at the University of South Carolina, points to signs of increased mutations, health issues, and population declines in organisms living in the Exclusion Zone such as birds, insects, and some mammals. Still other research teams have found no evidence that radiation is reducing certain other animal populations in the Exclusion Zone, including elk, red deer, and wild boar. Even in highly contaminated areas, the mammal populations seem to be steady.

These disparate results could have several explanations, including varying research methods and the effects of confounding factors in the surrounding environment. The different results among species also likely comes down to biological differences, says Adam-Guillermin. A given creature’s response to radiation depends on factors like their unique sensitivity to radiation and efficiency in dealing with DNA damage, along with the specific environment, and the creature’s ability (or inability) to migrate.

Trees, for instance, can’t just walk away from the still highly contaminated Red Forest near the Chernobyl plant. They can accumulate high levels of radiation when taking up nutrients from the soil, says Megan Dillon, a Ph.D. student at North Carolina State University who worked on both dog studies. This could help explain why scientists have found increased mutation rates in pine trees in the Exclusion Zone, for example.

An abandoned dog: