One of the most fascinating phenomena in the living world is the complex process of migration.
Various animals across the world undertake these monumental journeys, sometimes thousands of miles
in length. We find migration patterns in all the major animal groups from birds to mammals,
reptiles to amphibians, and even in some insects, like the monarch butterfly. The oceans of
this beautiful planet earth are interconnected making it possible for marine animals to travel
vast distances to complete their own migrations. Scientists have tracked migratory patterns in gray
whales, orcas, seals, jellyfish, sea turtles, and even some species of fish, like the blue marlin.
The intricate process of migration is still a mystery in many ways.
Migrations are usually completed seasonally or annually and are typically performed to
either find food or locate a safe place to breed and raise their young. Often scientists don't
know exactly what triggers an animal to start its migration and they can only guess how each animal
knows where to go and how to get there. Migratory patterns might even appear random at first glance,
but on closer examination a clear purpose and design can be seen guided by the hand of God.
For example, after a migration of over 10 000 miles, the female leatherback turtle will actually
return to the very beach where she was hatched to lay her own eggs. How did she recognize the
location of that specific beach and navigate back to it decades later? It's an unanswered mystery.
What causes these animals to migrate? Is it changes in sunlight, temperature,
or food supply that trigger these trips or some internal knowledge in each animal letting them
know it's time to leave? Scientific study of each migrating creature allows us to learn
more. Let's go along for the ride with a mighty grey whale on its annual migration.
The grey whale is a type of Baleen whale that reaches lengths of up to 50 meters or
49 feet and weighs up to 41 tons or 90,000 pounds. Grey whales typically
live between 50 and 70 years and they get their name from the gray patches on their skin.
Each year gray whales take the longest migration path of any mammal on earth traveling around
19,000 kilometers or 12,000 miles by the time their expedition is complete.
Most grey whales birth their calves in January in the warm sea waters of the pacific ocean near
Mexico. Then comes springtime the whales begin their epic journey traveling northward together
in groups called pods. They can travel up to 160 kilometers, or 100 miles, a day on their way to
their summer feeding grounds. Their destination? The cold, arctic waters off the coast of Alaska.
This area is rich with the grey whale's main source of food; small shrimp-like crustaceans.
Once they arrive in the far north, the grey whales begin to eat. Throughout the summer the whales
must eat constantly taking in well over one ton of tiny crustaceans and plankton each day. The
plentiful food helps them prepare for the fall when they make their return journey another 10,000
kilometers or 6,000 mile trek back south to the warmer waters from which they came.
The weight they gain also helps during their journey and throughout the breeding season
when they will eat very little and live off the fat stores developed during these summer months.
It's not uncommon for a grey whale to lose 25 to 30 percent of its body weight during its journey
south. So why don't the great whales just stay in the north where the food is so plentiful? Why
migrate south at all? The move to warmer waters in the south is actually vital for the survival
of the species. The full-grown whales have enough fat to keep them warm in the cold arctic waters
but the newborn calves do not. The mild salty waters of the south allow the calves to keep warm
while they gain weight for their own trip north. This cycle of birthing, migrating, eating,
migrating, and birthing continues without fail every year. We don't know for sure
how the whales know when it's time to migrate and it may be a combination of several factors.
The hours of sunlight increase in the spring and decrease in the fall.
The temperature of the ocean waters fluctuate and the local food supply varies by season.
Some scientists believe that grey whales have an internal biological clock that
tells them when it's time to migrate and an internal compass that tells them where to go.
Grey whales tend to migrate along the coastlines close to the shore. Staying near the coast may
also help them navigate during their months-long trek. Because of this nearshore migration,
often within two to three kilometers or one or two miles of the coastline, scientists and spectators
can easily observe this annual voyage. Off the west coast of the United States and Canada,
tourists and residents alike look forward to the time each year when the whales pass by, reliable
as the changing of seasons. Scientists study the roots and patterns of migrating animals to better
understand the forces that prompt these journeys. As you can see there is still much for us to
learn about animal migrations. These mysterious voyages continue year after year on land, in air,
and beneath the ocean waves. This fascinating topic will inspire us for years to come.