Fun fact! Walrus whistles are what were used as ambient spooky background noises during jungle scenes in the second Jurassic Park film!
The sound recordists got pelted with bits of half eaten fish when they were recording(the walruses were rewarded with fish for whistling). Sound supervisor Gary Rydstrom said “the hardest part was not screaming”
Fun fact: This is why sailors believed in sirens.
You can argue, but it’s actually true.