He has a stutter, lives in a zoo and can speak animal- Fantasy possibly YA

I read this book years ago when I was in 8th grade. It's about this kid who has a massive stutter and not the usual "s-s-sorry" but a "I went to- went to, I went to the..I went to the store today- the store today" style stutter. He had an older brother who was a jerk and had a superiority complex that his dad definitely made bigger by having them compete all the time. Whoever won got to hold onto a monkey paw.
They live on an island that their dad turned into a large Zoo and at some point the MC hurts his hand and a magic Leopard or Jaguar licks the wound and heals it, causing him to now understand animals. The most I remember after that is: (spoilers, I do clearly remember how it ends)

* He hears mice talking and assumes theyre intruders and causes his dad and brother to panic a bit- which ends with his dad taking the monkey paw and giving it to his brother
* There's a girl who's sort of like a love interest, he shows her his scar and she feels it.
* He tries to save some rodent from being eaten by snakes but fails
* He helps the animals overthrow the Zoo and there's a line about the girl looking for him in the treeline before evacuating

Whenever I try to search for it in google nothing helpful comes up, so I'm hoping someone here knows what I'm talking about. Thank you for reading my post!