Everybody likes Walnuts, especially squirrels. We eat English Walnuts, but our Black Walnuts (above) are similar, if less cultivated. The wood is even more valuable, and lumbering has left few big trees in the wild. The related Hickories (below) are known for the finest firewood to be had.
The Shagbark Hickory nuts above were almost ready to fall when this picture was taken. A week later, they were on the ground, but by the time I was back with the camera, there wasn't much left. The squirrels had been busy, gnawing through the heavy husks, and then into the nut shells to extract the meats within. It looked like a crime scene, but I can't really blame the rodents: I'm sure I'd have done the same.
Below are fruits of the Mockernut Hickory, also worthy of the incisor approach.
Other husks are not so rewarding...