Squirrels Are Somehow Surviving After Eating Poisonous Mushrooms

Squirrels in Japan have been found repeatedly eating highly poisonous mushrooms that could harm them, leaving a scientist and photographer who observed them stumped.

Images published in the journal Frontiers in Ecology and the Environment on December 1 show Japanese squirrels eating different species of amanita mushrooms, which are poisonous to humans and many animals.

When consumed by humans, the mushrooms can cause delirium, hallucinations, seizures, comas and even death in some rare cases.

The scientist and photographer who documented the squirrel behavior said in the journal entry that the animals returned to eat the poisonous fungi over several days, suggesting that they could consume them safely.

Squirrel eating Fly Amanita mushroom
A Japanese squirrel from the study eating an amanita muscaria or fly amanita mushroom. The mushrooms are toxic and the squirrels were documented eating them safely. Koichi Gomi

The most famous kind of amanitas, amanita muscaria, also known as fly agaric or fly amanita, have been referenced in popular culture, including the computer game series Super Mario.

The visual distortion of objects is one common symptom of consuming the mushroom which, as the authors of the research noted, informed the hallucinatory elements in Lewis Carrol's 1865 novel Alice's Adventures in Wonderland. The protagonist is given some mushroom to eat in the book.

Kenji Suetsugu, an associate professor at in the Department of Biology at Kobe University, worked with photographer Koichi Gomi on the findings.

"I was genuinely surprised. I was afraid the squirrel might get an upset stomach," Suetsugu told Newsweek. "But, the same individual squirrel returned a few days later to continue feeding on a panther cap mushroom, leading us to conclude that it is highly probable that these squirrels can safely consume poisonous mushrooms."

The authors said their observations suggest there is a symbiotic relationship between the squirrels and toxic mushrooms. Not only do the squirrels likely benefit from eating the mushrooms, but they could be helping distribute mushroom spores too.

Suetsugu said the poison found in the mushrooms could still deter other animals who might not have what appears to be a mutually beneficial relationship.

It is thought that mushrooms such as the amanita are poisonous to dissuade animals from eating them.

At the present time, the symbiotic relationship between the squirrels and mushrooms is hypothetical, however. The research poses numerous questions warranting further study, the authors said.

How can squirrels survive eating toxins "deserves future study. As it stands, we cannot answer the question," Suetsugu said.

"Some other squirrels are also known to eat poisonous mushrooms, but the main point of this study is that we were able to figure out that the same individuals eat them on a daily basis," he said.