# Dogs in the Chernobyl exclusion zone

After the 1986 nuclear disaster in Chernobyl, the regional domestic dog population suffered from environmental pollution originating from the radiation. This disaster made the environment highly mutagenic, leading to various evolutionary processes including, but not limited to, bottlenecks, directional selection, and higher rates of mutation resulting in evolutionary trajectories that differ from unexposed animals.

## History
### Origin of populations

The exact origin of the populations of dogs living in the Chernobyl Nuclear Power Plant (CNPP) and the surrounding areas of the Chernobyl Exclusion Zone is unknown. However, it is hypothesized that these animals are the descendants of pets left behind during the original evacuation of Pripyat. While many of these original pets population were killed by the Ukrainian Ministry of Internal Affairs to prevent the further spread of radiation, the remainder survived to reproduce. There are currently two geographically and genetically distinct populations of dogs in the area, one in the CNPP and one in Chernobyl City.

### Population characteristics

At least 302 feral dogs live around the Chernobyl Exclusion Zone (CEZ). However, there are projections of up to a thousand individuals due to the present differences with the nearby populations (10 miles away). They differentiate from populations only 16 km away. At least 15 families are living inside the area mostly related to shepherd breeds such as the German shepherds, characteristics shared by other feral dogs living in Eastern Europe.

## Evolutionary processes
### Rapid evolution

The dogs suffer from radiation that may differentiate them genetically from the population of CEZ with their surroundings. Nevertheless, processes such as the high likelihood of inbreeding can lead to difficulties at the moment of analyzing their genome. In addition, the conditions of their habitat, human control in the access to the CEZ, may simulate an island habitat in terms of evolutionary processes such as isolation.

### Mutations

Despite the evidence of genetic differentiation mainly due to the radioactive environment, there is no support for pinpoint radiation as the primary driver of genetic differentiation; the evidence serves as insight for further research in these populations. Some regions of the genome indicate that they can be driven by directional selection. 391 outlier loci are influenced by directional selection, with at least 52 candidate genes

### Comparisons with unexposed populations

Genetic signatures of the Chernobyl dog populations have been compared to both pure-bred and free-breeding dog population genetic structures. The Chernobyl populations did not share increased similarity to pure-bred dogs, indicating that the populations of dogs of Chernobyl have not been inundated with individuals that are modern pets. Instead, this population is similar to free-breeding populations, indicating that the population has been established at least since the disaster in 1986. However, the Chernobyl dogs show enough differentiation from these populations that they can be used as a unique entity for further genomic study.

## Relief efforts

Since 2017, the Clean Futures Fund has implemented annual clinics in the Chernobyl exclusion zone to vaccinate, spay, and neuter the dogs of Chernobyl. This effort is made to reduce the risk of rabies passing to workers and tourists, to decrease the population size of the dogs, and to minimize the suffering that the dogs experience. The dogs in the zone are able to recognize the uniforms of CFF personnel, and often avoid capture. For this reason, the CFF changes the color of their uniforms every year in order to vaccinate, spay, and neuter the dogs.