Little Tiny Teeth, by Aaron Elkins

Set in Peru, this one is about headhunters, drug smuggling, greed, and boating down the Amazon. It's all good till Our Heroes get kidnapped by drug smugglers ... and then released because the leader isn't that bad of a guy after all. Or something.

Still the rest of the story is good. I like Gideon.

Creepers, by Joanne Dahme