“I heard that squirrels will only eat one side of a buckeye because one side is poisonous and the other isn’t. Is that true?”
We checked Grizmek’s Encyclopedia of Mammals: Volume 3, the Peterson Guide to Edible Wild Plants, Warner Shedd’s Owls Aren’t Wise and Bats Aren’t Blind, The Ohio Nature Almanac, and Osmond P. Breland’s Animal Life and Lore to see if there was any mention of this bit of folklore. While we learned a few interesting facts about squirrels (that they aren’t strict vegetarians, for example – along with nuts, seeds, and mushrooms, squirrels will sometimes also eat eggs and insects), we didn’t find any mention of squirrels only eating half a buckeye.
Looking around online, we found that Cindy Decker, a writer at the Columbus Dispatch, had already tackled the question. She went all the way back to the 1913 edition of The North American Journal of Homeopathy. In the journal, Dr. H.L. True writes of the experiment their friend Mr. C.H. Morris did on squirrels. Morris caged three squirrels and provided them with buckeyes to eat. The squirrels did not all start eating on the same side of the nut. While none of them ate their whole buckeye in one sitting, they would eventually go back and finish it when they got hungry enough.
According to a fact sheet provided by the Ohio Division of Forestry, while the buckeye can be poisonous to people, it doesn’t affect squirrels. It’s not their preferred food, but they will eat it if they can’t find anything better.