How does the rabbit know when to change its color?

You're likely thinking of the snowshoe hare, a rabbit species that changes color with the seasons. They don't actually *know* when to change, it's a biological process triggered by the changing amount of daylight.

Here's how it works:

* Melatonin: As the days get shorter in fall, the snowshoe hare's body produces more melatonin, a hormone that influences the production of melanin, the pigment responsible for fur color.

* Melanin Production: More melatonin triggers the production of darker melanin, causing the hare's fur to turn brown or gray to blend in with the autumn landscape.

* Spring Changes: As the days get longer in spring, melatonin production decreases, and the hare's body switches to producing lighter melanin, resulting in its white winter coat.

So, it's not that the hare is consciously aware of the changing seasons and decides to change color. It's an automatic response driven by hormonal changes in response to the changing amount of sunlight.