“Because snakes don’t move that much, and they spend their time in one particular local area, the level of radiation and contaminants in the environment is reflected by the level of contaminants in the snake itself,” Hannah Gerke, a lead author on the study, said.
Animals, plants, or other life forms whose health provides insight into environmental health are known as bioindicators. For example, frogs, with their permeable skin and limited abilities to detoxify, are bioindicators of environmental pollution. And lichens, which have no roots and rely on nutrients from the atmosphere, are bioindicators of atmospheric pollution. Gerke’s recent study suggests that rat snakes may be useful bioindicators of radioactive contamination in nuclear disaster zones. But that does not necessarily mean that Fukushima’s environment or its snakes are languishing.
What did the snakes reveal? Some of the snakes’ radiation exposure in the Fukushima Exclusion Zone hails from contaminated prey they eat, but most—80 percent—comes from contact with contaminated soil, trees, and plants.
“Understanding how contaminants move throughout an ecosystem and how they move in different animals throughout the food web gives us a better picture of the impacts [of the nuclear disaster] to the ecosystem,” Gerke said.
An individual snake’s exposure is related not only to the small region in which it spends time but to its behavior. For example, snakes that spent time in abandoned buildings had lower doses relative to those that did not, suggesting that buildings may act as contamination shields. Also, snakes that spent more time in trees had lower doses relative to snakes that spent more time on the ground. Gerke hypothesizes that species that spend their time primarily on the ground are potentially more vulnerable to negative health effects of radiation, should negative health effects for snakes exist.
The current study was the first to describe home range size, movements, and habitat selection of Japanese rat snakes. The results suggest that these animals could be effective bioindicators of local environmental contamination in nuclear disaster zones. But many questions remain. For example, will scientists be able to develop models clarifying the link between habitat use, radiation exposure, and radiation accumulation? If so, they might provide insight into the health effects of chronic radiation exposure in animals or humans.