Where do platypus live?

Newly hatched mammals (Reddit link)

When I was in Oceanography grad school I had a class called Marine Nekton. I tried to get the professor to let me present a paper about platypus but he refused. Said it was because they live in fresh water. Harumph. I bet they could live in salt water if they wanted to. He was probably just afraid of the blank looks from my classmates with undergraduate degrees in stuff like Psychology when I tried to explain why there's no electric field inside a hollow conductor.

Back then I was interested in the hearing of mammals that go from water to land. Seals, otters, walruses, scuba divers, things like that. I was looking for any papers about how animals that do that deal with how different it sounds in and out of the water. I had an idea to make a theater that simulated what it would sound like to be underwater. I'm still up for doing that if the Navy wants to give me a grant. I hypothesize that humans could learn to judge distance and direction at the faster speed of sound underwater if they just had enough practice. It's possible the Navy has already proven this but they are really secretive about that kind of research.

So anyway, the platypus has terrible hearing but they are as fascinating as sharks with regards to electricity. They close their eyes and nose and ears when they hunt, feeling around for shrimp in the mud with those bills. They have an electrical sensor array in there. Platypus are so sensitive to electric fields the scientists who study them in captivity have to build the platypussary inside a Faraday cage.

That's right, I said platypussary. That is possibly my favorite word of all time. If anybody wants to get some platypus and study them let me know because I would love to design and build a platypussary. That would look so awesome on my resumé.

Before I read the paper about the platypussary I never really knew how big a full grown platypus is. I pictured it around otter or beaver size. They are much smaller than that, only as big as a small house cat. I thought you ought to know.