What Does the Fox Say?

Q: If you change the third letter of WOLF to an O, you get the sound made by a dog — WOOF. Name a six-letter animal and change the second letter to get the sound made by a completely different animal. What is it?

If you take the sound the first animal makes and you change one letter… well, I’m not saying anything more.

Edit: Rabbits are pretty silent.

A: RABBIT, RIBBIT