Guessing your niece’s age from the observation that she is watching you type and she insisted you post the joke, I think I must have been around her age when my dad told that joke to me.
But really if you want to catch a polar bear - You get a whale whisker (it’s kind of like a spring that straightens out) you wrap it into a coil and you freeze it in some seal lard. You leave it out for the bear. The bear swallows the piece of lard whole. It unfreezes in his stomach. The whale whisker straightens out piercing two holes in the bear that are incompatible with life more often then not. Cook the bear to taste and enjoy. That’s how the tribals do it; you could also just use a gun.
Up in northern Arizona near the extinct volcanos, there is a huge amount of volcanic ash. So, the same story works there only with a black bear, and “ash-hole.”