Correct Answer - D
Animals use seasonal variations in light intensity and photoperiod to time various activities. Birds of colder areas of Northern Hemisphere begin their Southward migration as the day lengths begin to shorten. Reverse journey is undertaken with the increase in day length. Turkeys, ferrets adn starlings breed in response to lengthening to days while goat, sheep and deer breed in response to shortening of days. Rabbits and guinea pigs are day neutral. In temperature and subtropical areas,cold blooded or ectothermic animals undertake hibernation as the day length begins to shorten.
