Winter is the ultimate challenge. As temperatures plunge across much of America, some animals escape to milder climates of the South, while others stay put and tough out the brutal cold and blizzards that blanket the North.

In autumn, change sweeps across America. As the trees greet the chill with a blaze of color, it's make or break time for the animals. Time to pull up stakes, make last minute preparations, and often find a mate before the cold sets in.

Summer is the time of plenty across America. It's a chance for animals to reap nature's bounty while they can. The year's young begin to explore their world, while new parents make use of the long days to make sure they grow up strong.

Across the continent, the land and its wildlife breathe in warmth and renewal. For some animals, courtship rituals begin to heat up battles for dominance break out. For others, it's the time to tend to brands new life.