Backyard Biology

Of squirrels and mushrooms

The squirrel was a regular in our yard. We saw her every day, and hardly even considered her wildlife. She was a neighbor, nesting in the tall red pine and raiding our bird feeder daily. She had a fondness for unsalted peanuts and bird seed.

One day the dogs and I were coming back from a walk, and the squirrel was in the middle of the yard standing on her hind legs staring us down, eating a mushroom. It was a toadstool, large and white, and the squirrel was holding it in two hands and relishing each bite.

I did a double-take, because I’d never seen a squirrel eat a mushroom before. But it made perfect sense; it solved a mystery. In the backyard I’d seen mushrooms toppled like tiny trees, and mushrooms with tiny bites around the edges. I’d wondered at mushroom bits placed carefully on stumps. I knew someone was foraging mushrooms for some purpose, but who?

It was the squirrel. It had always been the squirrel.

I had an instant newfound respect for this familiar rodent of the yard. Mushrooms are not to be trifled with, and mushroom identification can be confusing. How did the little critter know which mushrooms to eat, and which to leave alone?

So I looked it up, you see. I couldn’t help myself. I had to know about squirrels and mushrooms, so I consulted the all-knowing Google. And the answer was so surprising, it reinforced what I already knew about truth being stranger than fiction. I wouldn’t dare make this stuff up, it sounds too far-fetched. But read on, because every word is true.

Squirrels don’t have to be masters in mushroom identification. Squirrels can eat any mushroom on earth, it turns out, even the poisonous ones. Famously in Japan, a squirrel was observed over time repeatedly eating a poisonous mushroom without coming to any harm. The Kobe University scientist who observed this speculated that there is a symbiotic relationship between the squirrel and the mushroom: the squirrel could be immune to the mushroom’s poison because it works in the mushroom’s favor to be consumed by the squirrel, who spreads its spores. The whole thing, he said, deserves further study.

But it gets weirder. Up north in Alaska where squirrels hibernate, they were observed storing mushrooms that were not only poisonous, but known to have psychoactive properties. The University of Alaska Fairbanks professor who noted this speculated that the psychedelics might help them get through the long dark winter.

So squirrels love mushrooms - all kinds of mushrooms - and mushrooms love them back. Mushrooms and other fungi are a crucial part of the ecosystem because they support other life. They decompose the dead materials - logs and leaves and things, and through all this decomposition, they add minerals to the soil. Mycorrhizal mushrooms live on the roots of plants and form a symbiotic relationship, helping their host plants absorb more nutrients than they would on their own and grow faster as a result.

If mushrooms save the forest and squirrels help mushrooms grow by eating them and spreading their spores, then squirrels are the unsung heroes of the forest. That’s what I’ve learned from all this.

And I never noticed any of it was happening until a squirrel ate a mushroom right in front of me. What else has been hiding in plain sight? Squirrels have the superpower of metabolizing poison that would kill a larger animal. Blue jays can mimic any bird they choose. Slugs can regenerate, and crows can count to four. The yard is more mysterious than you could ever imagine.