Here are two playful ways to say it for a 6-year-old:
Some places are chilly, toasty, splashy, or sandy — and animals put on nature’s costumes and act differently so they can live there! That’s why we see so many amazing, silly, and surprising animals.
Places can be cold, hot, wet, or dry. Animals change their fur, feathers, colors, or tricks — like wearing coats, sunglasses, or rain boots — so they can be comfy. That’s why there are so many different, awesome animals!