Although in many places December so far hasn't been too cold, there are still plenty of people who are packing up their things and are heading down south for the winter. There they will escape the nor'easters and Alberta Clippers of the north and instead take refuge in the palm trees, sand, and green grass of the south. Animals go through migrations too as I'm sure you know, but you'll find that one's definition of "migration" depends on how you look at it.
Most of the time when we think of migration, the first animal that comes to mind is birds, as they fly from cold northern regions to warm southern areas in the fall the reverse route in the spring (I previously posted about fall bird migrations, check it out here).
But it doesn't have to be cold to trigger migration. For African elephants, they follow the rain. As their native lands dry from lack of rain, the elephants move to areas that still have green vegetation to eat (the grass really is greener on the other side!). Once the rainy season begins, the elephants will return to their newly-greened homes.
And food isn't the only reason for migration either. For the monarch, who doesn't hibernate like the rest of its butterfly cousins, they have to fly nearly 3,000 miles each year to Mexico to escape freezing in the winter. Others migrate in search of suitable breeding grounds; freshwater rivers for the Chinook salmon and Florida beaches for the loggerhead sea turtle.
Nor is migration always in a north-south orientation. Elk and mountain goats practice what is called altitudinal migration; they move from higher to lower elevations as the snow begins to fall.
Migrations don't even have to occur over a long period or distance! Some migrations last only 24 hours, as is the case with the tiny shrimp-like krill that live in the ocean. Krill migrate 1500 feet daily from their daytime protected depths of the ocean to the surface of the ocean under the cover of night to feed while avoiding the keen eye of predators.
So I guess when you think about it, I could consider my 9:00pm raid on the refrigerator a kind of nightly migration; there's no food on the couch, so I have to move to the refrigerator where there is food. Now if I could just burn the same amount of calories as a Arctic tern that has just migrated from the north to the south pole...