Wild animals have free range around northern Ukraine’s Chernobyl nuclear plant, the site of the world’s worst nuclear accident, which spread radiation throughout the region in 1986.

Studies have hinted that significant populations of European gray wolves and other large creatures live in the Chernobyl Exclusion Zone, the roughly Rhode Island-sized, 1,000-square-mile section from which people were evacuated and can no longer live.

While clear of humans, animals are not free from radiation and its health effects, an active and at times controversial area of research. Many questions remain about the extent to which radiation causes mutations in various species, and whether these could be spread outside the zone. (Related: Animals Rule Chernobyl Three Decades After Nuclear Disaster)

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