What happened to dogs left behind at Chernobyl

A population of wild dogs living near the Chernobyl exclusion zone is now giving scientists a glimpse into how long-term radiation exposure affects generations.

The radiation exposure still being emitted in Chernobyl decades after the 1986 nuclear disaster may have fundamentally altered the genetics of dog populations, according to a study published Friday in Science Advances. Furthermore, the genetics within dog populations that have been exposed to differing levels of radiation are also distinct from one another, the researchers said.

The dogs still living around the exclusion zone are likely descendants of pets left behind after residents surrounding the Chernobyl power plant fled the region in a hurry, leaving behind all their belongings, including their four-legged companions, Tim Mousseau, a professor of biological sciences at the University of South Carolina, told ABC News. The radioactive contamination devastated wildlife populations in the region, but some survived and continued to breed.

Researchers used preserved blood samples collected from more than 300 between 2017 and 2019 in locations with varying levels of contamination by the Chernobyl Dog Research Initiative as the organization has been providing veterinary care, according to the study. The volunteers began treating and sterilizing the dogs around the same time that construction began for the new safe confinement facility for the nuclear reactor that failed, and there was concern that the dogs living in the area may be a problem, Mousseau said.

Many of the effects the researchers have seen in the dogs and other animals parallel what has been observed in the past with atomic bomb survivors from Japan during World War II, Mousseau said.

For instance, they have increased rates of cataracts, because the eyes are the first tissues to show signs of chronic exposure to ionizing radiation, Mousseau said.

Scientists are also looking for other developmental abnormalities, such as tumors, smaller brain sizes and changes in symmetry, Mousseau said.

The researchers aimed to distinguish the different populations of dogs that live in and near the power plant as well as in Pripyat, the abandoned town about two miles away, Elaine Ostrander, distinguished senior investigator at the National Institute of Health's Human Genome Research Institute, told ABC News.

The dogs that live in Chernobyl city have a background of boxer and Rottweiler, while the dogs in Slavutych have more Labrador retriever in them, Ostrander said.

Wide genomic variations within and across geographic locations across the Chernobyl Exclusion Zone, suggest the dogs live close to one another, move between sites and breed freely, the study showed. Researchers are now poised to determine the genetic progression of the dogs in the past several generations and look at how they have survived and propagated through that time, Ostrander said.

Although exposure to ionizing radiation is known to elevate genetic mutation rates across various plant and animal species, it is still unclear how larger animals may be impacted at the population level, according to the study.

The unique genetic diversity of these dogs makes them ideal candidates for future studies seeking to understand the long-term genetic health effects of highly radioactive environments on populations of large mammals, especially in understanding the biological underpinnings of human survival in regions of high and continuous environmental assault, the researchers said.

Even in the shadow of war, researchers and volunteers were able to venture to Chernobyl to treat about 125 animals and obtain more samples, Mousseau said.

These types of samples have only existed "once in human history," exciting scientists for the prospects of the findings to come, Ostrander said.

"It was a dream come true for me to be able to do some really sophisticated, advanced genetics in a way that had never been done before in this setting and on a model organism," Mousseau said. "What could be a better model for humans than dogs?"