Petulia

Petulia was the name of a walrus that frequented a Zoo in California. Ben Burtt used her vocalizations as a basis for Chewbacca's voice, alongside other animals.

Tim Veekhoven and Mark Newbold, in their blog Drawing from the Present: Familiar Creatures in a Galaxy Far, Far Away also mentioned that a walrus was involved in voicing Ponda Baba, although they weren't sure if it was Petulia.