In the spring of 1986, in their rush to flee the radioactive plume and booming fire that burned after the Chernobyl power plant exploded, many people left behind their dogs. Most of those former pets died as radiation ripped through the region and emergency workers culled the animals they feared would ferry toxic atoms about. Some, though, survived. Those dogs trekked into the camps of liquidators to beg for scraps; they nosed into empty buildings and found safe places to sleep. In the 1,600-square-mile exclusion zone around the power plant, they encountered each other, and began to reproduce. “Dogs were there immediately after the disaster,” says Gabriella Spatola, a geneticist at the National Institutes of Health and the University of South Carolina. And they have been there ever since.
Spatola and her colleagues are now puzzling through the genomes of those survivors’ modern descendants. In identifying the genetic scars that today’s animals may have inherited, the researchers hope to understand how, and how well, Chernobyl’s canine populations have thrived. These findings may reveal some of the long-lasting effects radiation has had on dogs’ health and provide insight into the traits that helped them avoid these worst consequences. The fates of dogs–bred and adapted to work, play, and lounge at our side–are tied to ours. The canines that we abandon when disaster strikes could be a reminder of what it means to live with the consequences.
One of the key canine groups the team is focusing on is based at what’s left of the power plant itself, and has likely weathered the highest levels of radiation of any dog population in the exclusion zone. The researchers are working to compare the genomes of those dogs with those of others living farther out, in Chernobyl City, a quasi-residential region about nine miles away that was evacuated after the blast, and in Slavutych, a less contaminated city roughly 30 miles out, where many power-plant workers settled after leaving their post. The study’s success is dependent on the spatial differences. The region’s landscape is “a patchwork of different radioactivity levels,” says Timothy Mousseau, a biologist at the University of South Carolina who’s been studying Chernobyl’s wildlife for more than 20 years, and is co-advising Spatola’s work. Which means that geographically distinct packs of dogs could, in theory, have distinct exposure histories, and distinct genetic legacies to show for it. Spatola and her colleagues are just starting their work. Spatola and her coworkers have already discovered evidence of differences in canines from the three reactor-adjacent groups.
The animals that the team sampled in Chernobyl City and Slavutych, the researchers found, look a lot like dogs you’d find elsewhere. They’ve been born of mixtures of modern breeds: mastiffs, pinschers, schnauzers, boxers, terriers. However, the population of power-plants seems to be more stuck in their past. There are more dogs in the area, but they still have strong ties to the German shepherd breed. This is a sign that animals have mostly stayed true to their roots. Elaine Ostrander (a geneticist at Spatola’s National Institutes of Health) says that these dogs are inbred and still heavily resemble a German shepherd. Elinor Karlsson (a Harvard and Broad Institute of MIT genomics expert) says that this pack could be something similar to a “time capsule” of the worst of the disaster. Perhaps this lineage of dogs has been stewing in the plant’s radiation for a dozen generations or more. Some could even be able to inherit mutations from the blast itself.
The long-ranging consequences of their exposures, though, aren’t yet clear. Repeated, heavy doses of radiation–which can mutate DNA, seed cancers, and irreparably damage the structural integrity of cells–can be, without question, “extremely detrimental to life,” says Isain Zapata, a biomedical researcher at Rocky Vista University. And over the decades, a wealth of studies has revealed serious health effects among some local animals: Birds have been found with tumors and unusually small brains; bank voles have battled cataracts and produced wonky, underperforming sperm. Even bees seem to struggle to reproduce. However, radiation is not always a problem for all animals. Many have avoided areas that are most saturated. And in some parts of the exclusion zone, some of them appear to be flourishing on terrain now largely devoid of humans and their polluting, disruptive ways. It’s difficult to predict where Chernobyl’s dogs might end up in this vast landscape. Domestic animals are dependent on humans and could suffer greater harm than any other animal when they leave. But that dependence also means that dogs are also less likely to chow down on wild, radiation-contaminated food, and may be well positioned to take advantage of the ruins we leave behind–and to mooch more when we start to creep back.
What the team finds next will be telling. Karlsson explained to me that scientists have spent many decades studying canine genomes. This makes it much easier to detect “when something is unusual.” The researchers might uncover mutations and sickness in the power-plant pack–a sign that the dogs’ genomes have been walloped by years of radiation, as those of some other animals apparently have. Karlsson believes that the researchers could also find evidence of genes that kept these dogs healthy in harsh environments, like a greater resistance to cancer. That, in turn, could bode well for us. Canine and human genomes are quite similar, and “domestic dogs have been a model for human cancer for a very long time,” says Shane Campbell-Staton, an evolutionary biologist at Princeton who studies Chernobyl’s wolves. Perhaps these dogs did not bend under pressure, but instead thrived.
One of the trickiest parts of the project will be figuring out which differences among the studied dog groups are attributable to radiation, rather than the ways in which the Chernobyl disaster completely remodeled the region and its ecosystems. Populations of plants, insects, birds, and mammals ebbed and flowed, affecting the availability of resources and the presence of predators. Sometimes, humans came with food and medical attention, but sometimes they also brought more dogs. There were many generations of animals that replaced one another, and the populations mixed and mingled. Olena Burdo, a radioecologist at the Kiev Institute for Nuclear Research, has worked for years to try to parse these many variables in her work with bank voles. She said that it is usually simple to see differences in populations when they are present in the wild. It’s just not always possible to pinpoint why.
Without perfect record-keeping of individual canines, the team can’t prove that the modern dogs they’re sampling are directly descended from 1980s dogs, either. Burdo told me she suspects that at least some of the power-plant dogs may be more transient than the researchers think. Researchers will struggle to determine the effect of radiation on generations if the dog populations being studied aren’t stable, flexible, or constantly changing. The power-plant dogs–the purported high-radiation cohort–may not really be a lineage born of the facility’s buildings after all.
But Ostrander is fairly convinced that the power-plant population has largely kept to itself. Life among the abandoned buildings is actually quite plush. Workers toss the dogs leftovers; tourists cheerfully sneak them snacks. In recent years, veterinarians joined forces to offer the dogs spay-and neuter and medical services, as well as vaccinations. The canines might not require much beyond that. Spatola said that the pack has become more independent and self-sufficient in recent years and might even have a tendency to return to its wilder, wolfish roots. This population of dogs, which started as pets, was left to survive the blast.
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