A new study, reported in the journal Functional Ecology and headed by Dr Ismael Galván from the Spanish National Research Council, is the first evidence that wild animals adapt to ionizing radiation and the first to show that birds have greatest problems coping with radiation exposure.

The Chernobyl disaster, which occurred on 26 April 1986 in Ukraine, had catastrophic environmental consequences. However, because the region remains heavily contaminated by radiation, it represents an accidental ecological experiment to study the effects of ionizing radiation on wild animals.

Ionizing radiation produces oxidative stress, but animals can adapt to their exposure with physiological adaptive responses. However, the role of radioadaptive responses in wild populations remains poorly known.

Previous studies of the level of antioxidants and oxidative damage at Chernobyl are limited to humans, two bird species and one species of fish. Because different species vary widely in their susceptibility to radiation, this limited data has made it difficult to study how wild animals adapt to radiation exposure.

At 8 sites inside and close to the Chernobyl Exclusion Zone, Dr Galván and his colleagues used mist nets to capture 152 birds from 16 different species: red-backed shrike; great tit; barn swallow; wood warbler; blackcap; whitethroat; barred warbler; tree pipit; chaffinch; hawfinch; mistle thrush; song thrush; blackbird; black redstart; robin and thrush nightingale.

The scientists measured background radiation levels at each site, and took feather and blood samples before releasing the birds. They then measured levels of glutathione, oxidative stress and DNA damage in the blood samples, and levels of melanin pigments in the feathers.

Levels of radiation in the study area ranged from 0.02 to 92.90 micro Sieverts per hour.

The findings show that with increasing background radiation, the birds’ body condition and glutathione levels increased and oxidative stress and DNA damage decreased. The birds which produce larger amounts of pheomelanin and lower amounts of eumelanin pay a cost in terms of poorer body condition, decreased glutathione and increased oxidative stress and DNA damage.

“The findings are important because they tell us more about the different species’ ability to adapt to environmental challenges such as Chernobyl and Fukushima,” Dr Galván concluded.

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Ismael Galván et al. Chronic exposure to low-dose radiation at Chernobyl favors adaptation to oxidative stress in birds. Functional Ecology, published online April 24, 2014; doi: 10.1111/1365-2435.12283