Snakes have been helping researchers to gauge current levels of radiation around the Fukushima Dai-ichi nuclear power plant in Japan where three reactors suffered meltdowns after the earthquake and tsunami in March 2011.
Radiation leaks forced tens of thousands of people to flee the area. Many have returned in the 10 years since but large areas around the plant remain off limits because of public health concerns.
Scientists from the University of Georgia found that rat snakes in particular, fitted with tracking and radiation measuring devices, offered a clearer picture of the residual radioactivity in the ecosystem around the nuclear plant.
Their study, published in the Ichthyology & Herpetology journal, showed that because of the rat snakes’ limited movement and close contact with contaminated soil, they were able to accurately reflect levels of contamination in specific areas.
“Our results indicate that animal behaviour has a large impact on radiation exposure and contaminant accumulation,” Hannah Gerke, one of the study’s lead researchers said.
She said the study showed that rat snakes travelled an average of only 65 metres a day.
The Japanese rat snake grows up to two metres in length and is non-venomous, feeding on small animals such as rodents, frogs and lizards. They are good climbers and often raid bird nests.
James Beasley, an adviser for the study, said snakes were good indicators of environmental contamination because they spend a lot of time in and on soil.
“They have small home ranges and are major predators in most ecosystems, and they’re often relatively long-lived species,” he said.
The researchers tracked nine snakes for more than a month in an abandoned area about 24 kilometres north-west of the power plant, checking on their location every few days to see if they were in trees or underground.
The latest study confirms last year's findings of a high correlation between the levels of radioactive elements in the snakes and in the soil of the areas in which they were found.
Ms Gerke said the levels of radioactive contamination are generally much lower now because of natural decay, but vary widely across different locations – even between places quite near each other.