The Wolf Keepers by Elise Broach
It's summer vacation time and Lizzie Durango is enjoying her time at the zoo where she lives with her dad, one of the head zookeepers. The zoo is near Yosemite National Park. Lizzie spends her days watching the newer wolves exhibit and writing and drawing about them in her notebook. She sees a boy steal a family's lunch, she becomes curious about him and tries to track him down. She finds Tyler living outside the elephants' exhibit and discovers he has run away from his foster family. Lizzie invites him to stay at the small apartment over her garage and the two begin to investigate the strange illness the zoo wolves are coming down with. They begin to question the involvement of the zoo vet. The two also become interested in finding John Muir's "lost cabin" which is reported somewhere in Yosemite. One night they follow Karen, who is taking two of the wolves away in the dark of night. They end up in Yosemite where they try to find the cabin of Muir before they go home to deal with the consequences of their actions.
To be truthful, I didn't really think I was going to like this book. However, when I started to read it and found out the setting was at the zoo, I began to like it more because I am a fan of Keatings "How to Outrun a Crocodile When Your Shoes Are Untied" series. Plus it is about wolves, something that is not typically written about in fiction (besides the topic of werewolves). I think this may be a book you might want to pick up and read.