The Chornobyl Dogs: Why Scientific Evaluation Must Accompany Population Management.

Nearly four decades after the 1986 reactor explosion, several hundred semi-feral dogs persist within the Chornobyl Exclusion Zone. Genomic work has characterised their population structure and shown that radiation-induced mutation does not, on current evidence, drive the differentiation between groups; the cause of that differentiation remains unresolved, and their epigenome has never been examined. These dogs are a potentially valuable model for chronic, low-dose, multi-stressor exposure, not because they are "radiation-adapted", a contested claim, but because they are a human-adjacent, densely sampled, pedigreed mammal for which comparative canine-human tools already exist. Since 2017, a humane sterilisation programme, carried out at the request of and in cooperation with the Ukrainian authorities, has reached near-complete coverage of the established populations. That programme was justified: dogs are formally prohibited in the zone, they injure workers, free-roaming animals inside an operating nuclear facility raise security as well as veterinary concerns, and reproduction was outpacing what the environment could support. Our argument concerns timing rather than policy. The scientific value of this population was never evaluated while it was still breeding, and the archived material that does exist, roughly 400 dogs including parent-offspring trios and repeat-sampled individuals, was assembled for population genetics rather than for the regulatory questions now worth asking. That archive should be analysed for methylation and expression now, as this is the only access to the population as it was. The animals themselves have not gone: several hundred identified dogs are still alive there, so sampling at veterinary contact and the retention of tissue at natural death or clinically indicated euthanasia remain possible, provided they are planned and funded in advance rather than improvised. More generally, the scientific evaluation of a population should accompany the decision to manage it rather than follow it, because sterilisation is not reversible at the population scale and an archive cannot be assembled retrospectively. We set out what such an evaluation requires at the outset of a programme. Its most concrete element asks nothing of the animals: a sterilisation clinic is the only routine access to a free-roaming population under anaesthesia, and the reproductive tissue it removes-the one material capable of addressing germline questions-is discarded as surgical waste.