A weird thing I have noticed is that MG animal stories are popular but they seem less common than they should be.
Also, they often have a much higher maturity level, making readers feel like the author understands they can handle tough things like cats fighting clan wars. (You didn't mention Guardians of Ga'Hoole, Warriors, Redwall, or Wings of Fire, which are all upper middle grade and deal with a lot of violence.)
A weird thing I have noticed is that MG animal stories are popular but they seem less common than they should be.
Also, they often have a much higher maturity level, making readers feel like the author understands they can handle tough things like cats fighting clan wars. (You didn't mention Guardians of Ga'Hoole, Warriors, Redwall, or Wings of Fire, which are all upper middle grade and deal with a lot of violence.)