rabbits moved to an area where the grass are naturally brown. There's a variation of rabbits, one that that's brown and one that's white.
These bunnies reproduced and created offspring more than the ecosystem can support. This caused competition between bunnies for their food.
soon after, these rabbits adapted to their environment, creating a generation that's fit for the environment with regards to the kind of food that they eat.
no more bunnies?
however, their peace was soon after disrupted by a hungry howling bird attacking them.
because of the rabbit's fur color, brown rabbits camouflaged to their surrounding making them hidden from the predator and survive. The white bunnies, on the other hand, was targeted by the predator which caused the decrease in numbers of bunnies with white fur.
Eventually, brown bunnies reproduced and became more common in the environment. They possessed the more advantageous trait by being able to camouflage with the environment and have a higher survival rate.