North American flying squirrels
They are adapted to fly at night because at night there is the most food and the least competition. Its pattern is regulated by an internal biological clock and not by external clues because even though the hours of darkness change throughout the year in North America, the flying squirrel continues to fly out at the same time no matter if it is light or dark. But external clues such as the light do come in helping the ground squirrel regulate its biological clock and adapt to its changing environment.
Fiddler Crabs
This crab only mates during a full moon or new moon as it is related to the best tidal periods. When the moon is full or new, the gravitational pull of the moon and sun are combined. At these times, the high tides are very high and the low tides are very low. These are called Spring tides. The adaptive value of this behavior is that the mating is timed to coincide with a Spring tide so the eggs can be released during a nocturnal high spring tide so that the tiny, swimming larvae are washed far out to sea. They develop out there for several weeks and then wash into shore.
