That saying applies to cats too, particularly Caitie-Belle.  She's small but scrappy, and she knows how to take care of herself, as you might expect from a cat who used to dig through garbage cans for food.

   One day soon after we adopted her, she was on the top level of the cat tree, looking out the window, when Kelly showed up.  The Big Guy has always dominated Lizzie, who is a classic fraidy-cat, and he probably expected to deal with his new housemate the same way.  He climbed to the level just below the top, and began taking that last step up.

   The Calico Diva lowered her ears, hissed, and threw a right cross that made Kelly back down.  The next time Kelly wanted to look out that window, he glared up at Caitie-Belle, but decided he didn't want a rematch.  Instead, he gathered himself and leaped from the floor directly to the windowsill.

   Once that little matter of who's-the-boss was settled, Kelly and Caitie-Belle eventually learned to share, (more or less).