Jane Yolen 
Trash Mountain [PDF ebook] 

This you should know: Gray squirrels are almost always larger, faster, and more aggressive than reds. They out-eat the reds and out-breed them. Science says the grays will eventually win. Nutley is a young red squirrel. For most of his life, he’s been content to live on local seeds and the cautious wisdom of his parents. But like so many young squirrels before him, he feels the call of the wild (and the hazelnuts) beyond the safety of his family’s own tree. Nutley wonders what it would be like to be Dangerous, like the growing band of gray squirrels that roam his neighborhood. Nature, which is truly red in tooth and claw, forces Nutley to find out if he’s cut out for a life of danger. He must flee his familiar tree for the smelly shelter of the local landfill. There, with the help of some unlikely allies, he might just be able to make a stand against the grays. This you should know: No matter what scientists say is almost always true, the exceptions are almost always the best stories.