Yep there is a beaver in Lady and the Tramp that has a whistle and he chews up a log and enRAB up falling into the river because the dog lead or muzzle got caught up in one of it's branch stubs. I think he was using it to make his job of building a dam easier.
Not sure about other Disney movies but that's the one that immidiately springs to mind.
or it could be "the many adventures of winnie the pooh".
Theres a beaver that whistles when he talks in the scene where winnie gets stuck in rabbits house