Scientists reveal how Chernobyl’s radiation is rewriting the DNA of wild dogs

From Catastrophe to Canine Community

In April 1986, the Chernobyl nuclear power plant in Ukraine suffered the largest nuclear disaster the world had seen at the time. Just ten days after the explosions at reactors 4 and 5, the atmosphere across Europe—and even as far as the United States—was still thick with cesium-137, iodine-131, and other radionuclides spewed out from the gaping, exposed radioactive core. Unsurprisingly, the local ecosystem was turned inside out by the event. Authorities established a 1,000-square-mile (2,600 km²) exclusion zone around the reactor, kicking out the people but leaving behind a teeming animal population. But what does this radioactive legacy mean for the animals that never left?

From Mice to Mutts: A Genetic Investigation

So far, the effects of local radiation had been studied mostly in small creatures like mice. Big mammals? Not so much. That gap was addressed by a team led by Timothy Mousseau (University of South Carolina, Columbia) and Elaine Ostrander (National Institutes of Health, Bethesda), who have spent years researching the genetics and distribution of the stray dogs living in and around the damaged Chernobyl zone. Their first findings were published in the March 3 issue of Science Advances.

Blood Samples and Survival Instincts

The investigation began in 2017, when researchers set out to collect blood samples from stray dogs in the region impacted by the disaster. Over two years, three clinics spread across the area gathered samples from 301 dogs. One clinic operated just next to the remains of the power plant—a site now populated only by workers handling the wreckage. The second clinic was in the mostly abandoned city of Chernobyl, about 9 miles (15 km) away. The third was farther out in Slavutych, 28 miles (45 km) from the site—a town built after the disaster to shelter the evacuated residents of Chernobyl and its irradiated surroundings.

Despite orders from the Ukrainian Ministry of the Interior soon after the disaster to cull all stray or abandoned animals to prevent further radioactive contamination, enough survivors seem to have slipped past hunters. Packs of these dogs gradually re-established themselves within and around the Chernobyl zone.

Unexpected Lessons from Mutant Mutts

The scientists analyzed the genetic signatures of these three dog populations, divided by their distance from the epicenter: far (45 km/28 mi), close (15 km/9 mi), and smack dab in the heart of the disaster.

• First lesson: As shown in earlier studies on small animals, the closer these dogs live to the plant’s ruins, the more evidence of irradiation they carry. Signs include deposits of cesium-137—a toxic radionuclide—found in their bodies. Levels of cesium-137 in dogs near the former plant were over 200 times higher than in dogs living just ten kilometers away in the city of Chernobyl.
• Second lesson: These three populations are not only genetically different from ordinary strays, but also distinct from each other. Of course, that doesn’t stop them from mingling—and, well, nature takes its course: DNA analysis revealed traces of genetic mixing across all three populations.

For Christophe Hitte, from the Dog Genetics team at IGDR (Rennes, France), this study marks only the beginning for American researchers:

“Now that they’ve thoroughly mapped out the dogs’ distribution areas and the genetic structure of the different populations, the team has a great toolkit to go further—for example, to examine how thirty years of radiation have impacted these populations. What allowed these canine bloodlines to survive? Personally, I think the genes involved in DNA repair must be more efficient in dogs under such harsh conditions compared to an average dog, which wouldn’t have survived.”

The research is definitely set to continue. It’s just the start of a huge genetic project that lies ahead for these scientists. As Christophe Hitte puts it, this situation offers a unique opportunity:

“A colony of relatively isolated dogs that have been breeding for 30 years in such a highly mutagenic environment makes for perfect material for a geneticist!”