Workers on a break watch a stray dog saunter by outside an administrative building inside the exclusion zone at the Chernobyl nuclear power plant on August 18, 2017 near Chornobyl, Ukraine. An estimated 900 stray dogs live in the exclusion zone, many of them likely the descendants of dogs left behind following the mass evacuation of residents in the aftermath of the 1986 nuclear disaster at Chernobyl. Volunteers, including veterinarians and radiation experts from around the world, are participating in an initiative called The Dogs of Chernobyl, launched by the non-profit Clean Futures Fund. Participants capture the dogs, study their radiation exposure, vaccinate them against parasites and diseases including rabies, tag the dogs and release them again into the exclusion zone. Some dogs are also being outfitted with special collars equipped with radiation sensors and GPS receivers in order to map radiation levels across the zone. (Photo by Sean Gallup/Getty Images)





A stray puppy walks along abandoned train tracks near the Chernobyl nuclear power plant on August 19, 2017 near Chornobyl, Ukraine. (Photo by Sean Gallup/Getty Images)





In this aerial view abandoned, partially-completed cooling towers stand at the Chernobyl nuclear power plant as the new, giant enclosure that covers devastated reactor number four stands behind on August 18, 2017 near Chornobyl, Ukraine. (Photo by Sean Gallup/Getty Images)





Jake Hecla (R), a graduate student in nuclear engineering at the University of California, Berkeley, uses a “frisker” Geiger counter to measure radiation on the paws and fur of an anesthetized stray dog before surgery as Portuguese veterinarian Filipe Pequito and volunteer Kerry Anne O'Connor look on at a makeshift veterinary clinic inside the Chernobyl exclusion zone on August 17, 2017 in Chornobyl, Ukraine. (Photo by Sean Gallup/Getty Images)





Workers walk past a tagged, stray dog inside the high-security “local zone” outside the new, giant enclosure that covers devastated reactor number four at the Chernobyl nuclear power plant on August 18, 2017 near Chornobyl, Ukraine. (Photo by Sean Gallup/Getty Images)





Anna Sovtus, a Ukrainian veterinarian working with The Dogs of Chernobyl initiative, tends to a stray puppy she had just washed in the bathroom sink at a makeshift veterinary clinic inside the Chernobyl exclusion zone on August 17, 2017 in Chornobyl, Ukraine. (Photo by Sean Gallup/Getty Images)





Administration worker Lyudmila Ivanovna greets stray puppies inside the exclusion zone at the Chernobyl nuclear power plant on August 18, 2017 near Chornobyl, Ukraine. (Photo by Sean Gallup/Getty Images)





Terry Paik, a veterinarian from San Diego, California, volunteering with The Dogs of Chernobyl initiative, prepares to neuter an anesthetized stray dog at a makeshift veterinary clinic inside the Chernobyl exclusion zone on August 17, 2017 in Chornobyl, Ukraine. (Photo by Sean Gallup/Getty Images)





A “frisker” Geiger counter used to measure radiation shows a reading of 1240 counts, approximately 20 times higher than normal, on the paws of an anesthetized stray female dog at a makeshift veterinary clinic operated by The Dogs of Chernobyl initiative inside the Chernobyl exclusion zone on August 17, 2017 in Chornobyl, Ukraine. (Photo by Sean Gallup/Getty Images)





Stray dogs loiter inside the high-security “local zone” outside the new, giant enclosure that covers devastated reactor number four at the Chernobyl nuclear power plant on August 18, 2017 near Chornobyl, Ukraine. (Photo by Sean Gallup/Getty Images)





Workers on a break pet a stray dog they have named Bulka outside an administrative building inside the exclusion zone at the Chernobyl nuclear power plant on August 18, 2017 near Chornobyl, Ukraine. (Photo by Sean Gallup/Getty Images)





Stray dogs seek a handout of food outside the workers cafeteria at the Chernobyl nuclear power plant on August 17, 2017 near Chornobyl, Ukraine. (Photo by Sean Gallup/Getty Images)





Stray dogs hang out near an abandoned, partially-completed cooling tower at the Chernobyl nuclear power plant on August 18, 2017 near Chornobyl, Ukraine. (Photo by Sean Gallup/Getty Images)





Dog catcher Aleksander Klimov releases a stray dog back into the wild inside the exclusion zone around the Chernobyl nuclear power plant after veterinarians with The Dogs of Chernobyl initiative had tagged, spayed and vaccinated it on August 17, 2017 in Chornobyl, Ukraine. (Photo by Sean Gallup/Getty Images)





A tagged, stray dog sniffs for food in a trash can outside the workers cafeteria inside the exclusion zone at the Chernobyl nuclear power plant on August 18, 2017 near Chornobyl, Ukraine. (Photo by Sean Gallup/Getty Images)





Jake Hecla, a graduate student in nuclear engineering at the University of California, Berkeley, and a volunteer with The Dogs of Chernobyl initiative, uses a spectroscopy device to measure gamma rays emitted from isotopes, including americium, which is derived from plutonium, and cesium lodged inside the body of an anesthetized stray dog recovering from surgery at a makeshift veterinary clinic inside the Chernobyl exclusion zone on August 17, 2017 in Chornobyl, Ukraine. (Photo by Sean Gallup/Getty Images)





Pavel “Pasho” Burkatsky, a professional dog catcher from Kiev, takes aim with a blow gun to shoot a tranquilizer dart at a stray dog in the exclusion zone around the Chernobyl nuclear power plant on August 19, 2017 near Chornobyl, Ukraine. (Photo by Sean Gallup/Getty Images)





Nastya Grabchuk (L), a Ukrainian medical student volunteering with The Dogs of Chernobyl initiative, and Meredith Ayan, Executive Director of SPCA International, a U.S.-based animal rescue non-profit, tend to stray puppies recovering from a sedative after surgery and vaccinations at a makeshift veterinary clinic inside the Chernobyl exclusion zone on August 17, 2017 in Chornobyl, Ukraine. (Photo by Sean Gallup/Getty Images)





A dog catcher holds a tranquilizer dart he had just used in an attempt to capture a stray dog inside the exclusion zone around the Chernobyl nuclear power plant on August 17, 2017 in Chornobyl, Ukraine. (Photo by Sean Gallup/Getty Images)





A stray dog stands at a monument outside the new, giant enclosure that covers devastated reactor number four at the Chernobyl nuclear power plant on August 18, 2017 near Chornobyl, Ukraine. (Photo by Sean Gallup/Getty Images)