L5 U1-4-2 Mysteries of Nature 2
Another amazing example of survival is the salmon[1].
Salmon spend most of their lives in the ocean, which is saltwater.
Yet, when it's time to breed[2], they do so in freshwater rivers.
Salmon can adapt their bodies to survive in both saltwater and freshwater.
When it's breeding time, they return to the same river where they were born.
It seems as if they have a built-in map that guides them for hundreds of miles.
Once they leave the saltwater, they don't eat.
They are determined to finish their journey, despite the many obstacles.
They swim against strong currents[3], jump over waterfalls and try to escape the claws[4] of hungry bears.
Many die along the way, but enough of them survive to breed and produce the next generation.
Once they have laid their eggs, they die, having completed their journey.
It seems that their purpose in life is just to reproduce.
Migration takes animals to new, more favorable[5] environments when the seasons change.
Some of these journeys are long and dangerous, along routes[6] with no obvious landmarks[7].
The longest migration is that of the Arctic tern[8].
It flies from pole to pole, twice a year.
If a tern achieves its average lifespan[9] of 20 years, the distance it has flown[10] will be equivalent[11] to a journey to the moon and back.
Humans also migrate, but seldom if ever for seasonal variations.
Unfortunately, human migrations are often due to human activities.
Since the beginning of the 21st century, large scale migrations have become a global problem.
Millions of migrants have had to leave their countries and look for new homes.
Many have died along the way or lived as refugees[12] in camps until they are admitted into a new country.
So the question remains as to how our global community will face these challenges.
