After the disaster at the nuclear
power plant in Chernobyl, Ukraine, in 1986, local residents were forced to
permanently evacuate, leaving behind their homes and, in some cases, their
pets. Concerned that these abandoned animals might spread disease or
contaminate humans, officials tried to exterminate them.
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And yet, a population of dogs somehow endured.
They found fellowship with Chernobyl cleanup crews, and the power plant workers
who remained in the area sometimes gave them food. (In recent years,
adventurous tourists have dispensed handouts, too.)
Today, hundreds of free-ranging dogs live in
the area around the site of the disaster, known as the exclusion zone. They
roam through the abandoned city of Pripyat and bed down in the highly
contaminated Semikhody train station.
Now, scientists have conducted the first deep
dive into the animals’ DNA. The dogs of Chernobyl are genetically distinct,
different from purebred canines as well as other groups of free-breeding dogs,
scientists reported on Friday in Science Advances.
“Do they have mutations that they’ve acquired that allow them to live and breed successfully in this region?”
It remains too soon to say whether, or how,
the radioactive environment has contributed to the unique genetic profiles of
the dogs of Chernobyl, scientists said. But the study is the first step in an
effort to understand not only how long-term radiation exposure has affected the
dogs but also what it takes to survive an environmental catastrophe.
“Do they have mutations that they’ve acquired
that allow them to live and breed successfully in this region?” said Elaine
Ostrander, a dog genomics expert at the National Human Genome Research
Institute and a senior author of the study. “What challenges do they face and
how have they coped genetically?”
Before researchers could tackle these questions,
however, they had to get the lay of the canine landscape.
“You have this region where there’s different
levels of radioactivity, there’s dogs living everywhere,” Ostrander said. “We
had to know who was who and what was what before we could begin our hunt for
these critical mutations.”
A
nonprofit and some vetsThe project is a collaboration among scientists
in the US, Ukraine, and Poland, as well as the Clean Futures Fund, a nonprofit
based in the US that works in Chernobyl. The nonprofit, which was established
in 2016, began as an effort to provide health care and support to power plant
employees, who still work in the exclusion zone.
“You have this region where there’s different levels of radioactivity, there’s dogs living everywhere… We had to know who was who and what was what before we could begin our hunt for these critical mutations.”
But the organization soon realized that
Chernobyl’s canine residents needed help, too. Although the dog population
boomed during the summer, it often crashed in the winter, when food became
scarce. Rabies was an ongoing concern.
In 2017, the Clean Futures Fund began holding
veterinary clinics for the local dogs, providing care, administering vaccines,
and spaying and neutering the animals. The researchers piggybacked on these
clinics to collect blood samples from 302 dogs living in different locations in
and around the exclusion zone.
Nearly half of the dogs lived in the immediate
vicinity of the power plant, while the other half lived in Chernobyl City, a
lightly occupied residential area about 14km away. (A small number of samples
came from dogs in Slavutych, a city built for evacuated power plant workers,
nearly 50km away.)
Two
distinct populationsAlthough there was some overlap between the
canine populations, in general, the power plant dogs were genetically distinct
from the Chernobyl City dogs, researchers found. There appeared to be little
gene flow between the two groups, suggesting that they rarely interbred.
(Physical security barriers around the power plant may have helped keep the
dogs apart, researchers noted.)
“I was completely surprised by the near total
differentiation between the two populations, the fact that they’ve existed
really in relative isolation for quite some time,” said Timothy Mousseau, a
biologist at the University of South Carolina and the other senior author of
the study.
The study will be a good starting point for further investigation of the effects of radiation, Boyko added. “They find where the interesting populations are,” he said, “where the interesting family groups are.”
The researchers also traced kin relationships,
connecting parents and offspring to identify 15 different family groups. Some
dog families were large and sprawling, while others were tiny, with more
defined geographic territories. Three family groups shared a storage facility
for spent nuclear fuel, scientists found.
New
frontiers in DNA studies“I don’t think anybody has looked at a single,
free-breeding dog population genetically at this level of detail before,” said
Adam Boyko, a canine geneticist at the Cornell University College of Veterinary
Medicine, who was not involved in the research.
The study will be a good starting point for
further investigation of the effects of radiation, Boyko added. “They find
where the interesting populations are,” he said, “where the interesting family
groups are.”
The power plant dogs and the Chernobyl City
dogs had mixed breed ancestry, but both shared stretches of DNA with German
shepherds, as well as other Eastern European shepherd breeds. The dogs from
Chernobyl City also had variants that are common in boxers and Rottweilers.
These segments of shepherd DNA might yield
particularly useful data in future studies, scientists said. Comparing these
sequences from the power plant dogs, the Chernobyl City dogs and purebred
shepherds living in nonradioactive environments might help researchers identify
radiation-related changes in the genome.
“This is a unique opportunity,” Mousseau said,
“a unique population of animals.”
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