The Dogs of Chernobyl

In April of 1986, a steam explosion in Reactor 4 of the Chernobyl Nuclear Power Plant in the Soviet Union ignited a fire that raged for 10 days and spewed vast quantities of radioactive particles into the atmosphere. Carried by prevailing winds, they were deposited over large swathes of Europe and even into North America.

The Soviet government closed the area around the power plant, and it remained officially off-limits until 2002, when it was opened to tourists. The current hostilities have forced its re-closure. Called the Chernobyl Exclusion Zone (CEZ), this 2,600-square-kilometer area was known before the nuclear disaster for its biological diversity. It has become the world's largest outdoor laboratory for the study of the effects of radiation on the flora and fauna.

Among animals that survived the Chernobyl disaster were dogs, those ubiquitous fellow travelers with humans. Now, an international group of scientists headed by Tim Mousseau of the University of South Carolina’s Department of Biological Science and Elaine Ostrander of the National Human Genome Research Institute at the National Institutes of Health in Bethesda, Maryland, has published a paper in the journal Science Advances, “The Dogs of Chernobyl: Demographic Insights into Populations Inhabiting the Nuclear Exclusion Zone,” conducting a genetic survey of 302 dogs in a zone that has been effectively shut to most traffic. This information is expected to forge new knowledge concerning the effects of radiation on large mammals in general.

Source: Credit: Clean Futures Fund+, used with permission.

Perhaps their most significant finding (which may not surprise some but is nonetheless worth documenting) is that the dogs of Chernobyl are genetically distinct from other dog populations in the world. Within the population of dogs in the CEZ, the researchers identified 3 main groupings. Those could then be split into subgroups similar to individual family groups, which showed long lines of relatedness in discrete locations around the disaster. The dogs closest to the reactor showed greater genetic difference than those at a further distance. The team also found that one population lived within the Chernobyl power plant site itself, and had been doing so since the explosion.

Ostrander and Mousseau hope to gain insight into what genetic differences might exist between CEZ dogs and those outside, which is complicated by the fact that unexposed dogs have been routinely brought into the zone by workers and visitors. The task requires great attention to the slightest variation in genomes between populations of dogs. For instance, some variations may involve coat density and color, which could represent an adaptation to the cold climate of the region or could relate to radiation-driven genetic variation, or a combination of the two. Until the researchers can get their detective work done, these questions remain unanswered.

I talked with Ostrander and Mousseau by Zoom on March 14. One interesting tidbit that emerged from the conversation was that they have found no evidence of rabies or other major viral diseases in the Chernobyl dog populations to date. Ostrander speculates that the absence of such highly communicable diseases might be due to the fact that these dogs tend not to live beyond 3 to 3.5 years, not long enough, if they have such viral diseases, to reproduce and transmit the disease.

One of the paradoxes of this study and others of its kind that rely on the testing of large numbers of dogs is that they are often tied to spay and neuter clinics, which if successful in their program to control the numbers of a given population of dogs through their sterilization, ultimately cause the demise of that population. The effects of radiation itself on fertility, namely whether it causes infertility, or, in fact, might increase fertility rates among the radiation-expose population, is unknown. The spay and neuter clinics obviously affect the evolution of the studied population by altering its reproductive capacity, but in the case of the dogs of Chernobyl, Mousseau and his colleagues are also regularly bringing hundreds of kilograms of dog food into the area. Given the war raging in Ukraine and the subsequent loss of tourism in the area, Mousseau and the clinic’s food offerings draw into their orbit a large number of dogs who rely on their food for their survival.

Source: Credit: Tim Mousseau / Clean Futures Fund+, used with permission.

Anecdotally, Mousseau said that up until 2015 or so, he and his crews of voluntary vets, technicians, and helpers often saw dogs of certain morphotypes roaming far from their home base and behaving, to all appearances, like their wolf cousins. Many of them appeared to be descendants of the Eastern European shepherds and pincers historically prevalent in the area. These dogs had learned to recognize the scrubs of the vets and their crews and how to evade them. How many of these semi-wild dogs or truly wild dogs existed, or still exist, is not known. However, many of them are believed to have opted to accept the food from humans who have routinely fed them. Most animals appear more than happy to at least supplement their diets by partaking of “freely” offered human cuisine. In the long run, this opting of an animal for an easily-obtained meal might well prove their undoing.

The spay and neuter program here had, apparently, stabilized the population before the war in Ukraine began. Ostrander and Mousseau emphasized that, in many ways, they are just beginning their inquiries into the genetic natures of these animals. We can only hope that the dogs of Chernobyl continue to survive to tell their stories.