In this scenario, as the average temperature increases and the winter becomes shorter, the environment may become less suitable for white-furred rabbits, which are typically adapted to snowy conditions where their fur provides camouflage and warmth. Conversely, brown-furred rabbits may have a survival advantage in a warmer ecosystem with less snow cover.
Therefore, the most likely scenario is:
The proportion of white-furred rabbits in the population declines.
This is because the white-furred rabbits may struggle to survive and reproduce in the changing environment, leading to a decrease in their population relative to the brown-furred rabbits.