What We Know About the Chernobyl Animal Mutations

You may wonder how, exactly, radioisotopes (a radioactive isotope) and mutations are connected. The energy from radiation can damage or break DNA molecules. If the damage is severe enough, cells can’t replicate and the organism dies. Sometimes DNA can’t be repaired, producing a mutation. Mutated DNA may result in tumors and affect an animal’s ability to reproduce. If a mutation occurs in gametes, it can result in a nonviable embryo or one with birth defects.

Additionally, some radioisotopes are both toxic and radioactive. The chemical effects of the isotopes also impact the health and reproduction of affected species.

The types of isotopes around Chernobyl change over time as elements undergo radioactive decay. Cesium-137 and iodine-131 are isotopes that accumulate in the food chain and produce most of the radiation exposure to people and animals in the affected zone.

Ranchers noticed an increase in genetic abnormalities in farm animals immediately following the Chernobyl accident. In 1989 and 1990, the number of deformities spiked again, possibly as a result of radiation released from the sarcophagus intended to isolate the nuclear core. In 1990, around 400 deformed animals were born. Most deformities were so severe the animals only lived a few hours.

Examples of defects included facial malformations, extra appendages, abnormal coloring, and reduced size. Domestic animal mutations were most common in cattle and pigs. Also, cows exposed to fallout and fed radioactive feed produced radioactive milk.

The health and reproduction of animals near Chernobyl were diminished for at least the first six months following the accident. Since that time, plants and animals have rebounded and largely reclaimed the region. Scientists collect information about the animals by sampling radioactive dung and soil and watching animals using camera traps.

The ​Chernobyl exclusion zone is a mostly-off-limits area covering over 1,600 square miles around the accident. The exclusion zone is a sort of radioactive wildlife refuge. The animals are radioactive because they eat radioactive food, so they may produce fewer young and bear mutated progeny. Even so, some populations have grown. Ironically, the damaging effects of radiation inside the zone may be less than the threat posed by humans outside of it. Examples of animals seen within the zone include Przewalksi’s horses, wolves, badgers, swans, moose, elk, turtles, deer, foxes, beavers, boars, bison, mink, hares, otters, lynx, eagles, rodents, storks, bats, and owls.

Not all animals fare well in the exclusion zone. Invertebrate populations (including bees, butterflies, spiders, grasshoppers, and dragonflies) in particular have diminished. This is likely because the animals lay eggs in the top layer of soil, which contains high levels of radioactivity.

Radionuclides in water have settled into the sediment in lakes. Aquatic organisms are contaminated and face ongoing genetic instability. Affected species include frogs, fish, crustaceans, and insect larvae.

While birds abound in the exclusion zone, they are examples of animals that still face problems from radiation exposure. A study of barn swallows from 1991 to 2006 indicated birds in the exclusion zone displayed more abnormalities than birds from a control sample, including deformed beaks, albinistic feathers, bent tail feathers, and deformed air sacs. Birds in the exclusion zone had less reproductive success. Chernobyl birds (and also mammals) often had smaller brains, malformed sperm, and cataracts.

Not all of the animals living around Chernobyl are entirely wild. There are around 900 stray dogs, mostly descended from those left behind when people evacuated the area. Veterinarians, radiation experts, and volunteers from a group called The Dogs of Chernobyl capture the dogs, vaccinate them against diseases, and tag them. In addition to tags, some dogs are fitted with radiation detector collars. The dogs offer a way to map radiation across the exclusion zone and study the ongoing effects of the accident. While scientists generally can’t get a close look at individual wild animals in the exclusion zone, they can monitor the dogs closely. The dogs are, of course, radioactive. Visitors to the area are advised to avoid petting the pooches to minimize radiation exposure.

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• Moeller, A. P.; Mousseau, T. A. (2009). “Reduced abundance of insects and spiders linked to radiation at Chernobyl 20 years after the accident”. Biology Letters. 5 (3): 356–9.
• Møller, Anders Pape; Bonisoli-Alquati, Andea; Rudolfsen, Geir; Mousseau, Timothy A. (2011). Brembs, Björn, ed. “Chernobyl Birds Have Smaller Brains”. PLoS ONE. 6 (2): e16862.
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• Wood, Mike; Beresford, Nick (2016). “The wildlife of Chernobyl: 30 years without man”. The Biologist. London,UK: Royal Society of Biology. 63 (2): 16–19. 

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