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Japanese squirrels can eat “poisonous” mushrooms

Mushrooms in the Amanita genus such as A. muscaria and A. pantherina have long been consumed by humans for their interesting psychedelic effects. Hallucinogenic symptoms from these mushrooms’ poison can distort the size of objects, as described in Lewis Carol’s Alice in Wonderland as well as cause other hallucinations, deliria, seizures and rarely death. There’s also a history of people consuming them as food but after a careful process of detoxifying them first.  

A common hypothesis is that poisons contained in the mushrooms have evolved to dissuade consumption by animals. An observation of Japanese squirrels (Sciurus lis) calls into question this idea, according to a new study from Kobe University.

Professor SUETSUGU Kenji and independent photographer GOMI Koichi watched an individual squirrel feeding on Amanita mushrooms several times over a few days in Nagano prefecture, Japan. The team concluded that the squirrel almost certainly evolved a way to safely eat the mushrooms. 

From these observations, a new theory emerged – it’s not always detrimental to a mushroom to be eaten. Much like eating the fruits of plants, sometimes an animal can actually benefit a mushroom. 

If the mushroom’s spores can survive the digestive tract, it is feasible that a squirrel could be dispersing the mushroom’s spores. In this regard, perhaps the “poison” could be acting to deter some animals, for instance those whose digestive tract would destroy the spores. Other animals that may have co-evolved with the mushroom would be rewarded for their dispersal with a tasty dinner.

Now professor Suetsugo wishes to carry the research further and investigate whether the squirrels are truly dispersing the Amanita spores or not. To do this, the scientists will check squirrel excrement for living spores. 

Understanding the relationship between these mushrooms and squirrels could unlock more information on forest ecology in general. Amanita mushrooms form important mutualistic relationships with different trees, helping to maintain forest ecosystems. 

“Perhaps Amanita mushrooms facilitate mutualisms with toxin-resistant squirrels, which can disperse viable spores, while deterring toxin-susceptible enemies, which could negatively impact spore survival. If so, potential dispersal of fungal spores by squirrels is analogous to a seed dispersal mutualism, in which a plant offers a reward to an animal as a seed disperser,” wrote the study authors.

“How do squirrels safely eat Amanita mushrooms? What role do squirrels play in Amanita spore dispersal? How would squirrel-assisted spore dispersal contribute to the establishment of ectomycorrhizal relationships within these ecosystems? These questions warrant further investigation.”

The research is published the journal Frontiers in Ecology and the Environment.       

Image Credit: Koichi Gomi

By Zach Fitzner, Staff Writer

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