There are two types of rabbits in this forest, white colored rabbits and brown colored rabbits.
Changes in Gene Pool
The white rabbits are dying before they can reproduce and the ones that can, are dying before they are even born.
The brown rabbits are surviving long enough to reproduce, have offspring, and pass on their trait of brown color which helps them camouflage in their environment and be able to survive, reproduce, and pass their genes to their offspring and so on.
The brown rabbits are increasing in number due to their survival and ability to reproduce where as the white rabbits are dying and decreasing in numbers.