Here are some other sounds walruses make:
* Barking: This is often used as a warning call or to communicate with other walruses.
* Snorting: This is often used as a way to clear their nasal passages.
* Grunting: This is often used as a way to express aggression or dominance.
* Clicking: This sound is used for echolocation, helping them navigate and find food.
So while the "moo" is the most iconic, walruses have a surprisingly diverse repertoire of sounds!