How did Jessie Coon James find food for Sam in My Side of the Mountain?

We first meet Jessie Coon James, a young raccoon, in the chapter called "In Which I Find a Real Live Man." Sam and Frightful adopted him, took him home and fed him, and he got fatter. Eventually he accompanied Sam to the stream. Jessie was good at digging up mussels. But Sam soon figured out how to use Jessie's techniques to his advantage. If left alone, the raccoon would dig up mussels, eat them, and then stop digging as soon as he was full. Sam let Jessie dig up the mussels, but then he would take the food away so that Jessie would keep digging. In this way, the raccoon's stash fed Sam first, and then Jessie could eat the rest. Sam wrote a recipe about mussel preparation in his notes.