Question

Why does sandburg compare the frog to the cat

Answer 1

it's more like fog hovers silently but never stays in one place too long just like like the cat it watches its surroundings silently but ends up moving

Answer 2

Cats typically sit on their haunches as they stare out at the world. This particular stance, unique to the cat, enables them to keep watch over their surroundings, but also be ready to take off if necessary. When a cat is on its haunches, they cannot be captured because it is easy for them to escape with a quick jump

Hope its right