I saw this cute little guy in the corridor between the rings and thought “oh how sweet it looks like it’s playing!” I walked a little closer and it made a cute dolphin noise before CHARGING AT ME. All my tribe mates heard was “awww look! Oh... OH NO NOT FRIENDLY!!!” It did a little damage but once I interacted with the “pet” option it went away.
Person who said they are Rockwell's spores, they are not,
They are an extraterrestrial superficially mammal like exostellar life form originating either in deep space or possibly on a "rogue" planet cast from it's solar system by massive gravitational forces.
Or, if you want the short version, they are big space beluga whales who came from another world