Why does my Pekingese store food like a squirrel?

My dog is 4 years old & she has always done this. I was just curious as to why she does this. She has favorites too. Like pizza crust & anything bread like, including biscuits. She won't eat for months & then terrorize the house with the food. She will growl & scream when she has the food in her mouth & she takes the treats out periodically to bother people. Why is this?