8 FASCINATING ANIMAL MIGRATIONS
Hi, it’s Katrina!
I’m sure you’ve all seen documentaries with the serengeti wildebeests getting attacked
by hungry crocodiles in the water!
But there are other, dramatic migrations too!
From intergenerational migration cycles to birds that fly millions of miles, here are
8 fascinating animal migrations.
8.
GREAT WHITE SHARK
Great white sharks are one of nature’s most imposing predators, and they also make one
of the animal kingdom’s longest-known migrations.
According to research conducted by Stanford University, which tracked 179 sharks, the
great white’s transoceanic journeys are as long as 3,100 miles (5,000 km) in one direction.
It was during this groundbreaking study that scientists first realized that these sharks
don’t spend their entire lives looking for food near coastal waters.
Every year around April, a number of great white sharks that live primarily off the California
coast, travel to a region halfway between the Mexican peninsula of Baja California and
the Hawaiian archipelago.
They arrive sometime during late Winter or early Spring and congregate in a Colorado-sized
portion of the Pacific that has been nicknamed the “White Shark Cafe.”
Cute name, right?
Until recently, the reasons for this migration remained largely unknown and puzzled scientists
for over a decade after the discovery was first made.
After all, the waters off the California coast that they call home are full of all kinds
of prey, such as seals and sea lions, ruling out the possibility that the sharks migrate
for food - so what are they all doing??
After all, what’s out there deep in the ocean for them to eat??
Researchers from the Monterey Bay Aquarium and Stanford University finally gained some
answers regarding the mysterious vertical migration when they tagged 36 sharks and followed
them during the annual trip.
In the process, they learned that the sharks swim and move along with a warm current that
generates off the California coast and leads to one of the most nutrient-rich biomes in
the world.
Turns out there is food there!
Until scientists physically followed great whites on their journey, they had assumed
that the destination was nutrient-poor, based on satellite images.
7.
CARIBOU
Caribou travel hundreds of miles every Spring in herds of up to 100,000.
They travel from winter ranges south of the Brooks Range in Alaska and from parts of Canada’s
Yukon Territory to calving grounds located on the foothills and coastal plain of the
U.S. Fish and Wildlife Service’s Arctic National Wildlife Refuge.
Caribou are sometimes delayed from reaching calving grounds due to deep snow and the delayed
melting of snow along their route.
In 1987, 2000, and 2001, calves were born along the migration route because of these
environmental issues.
Once the calves were able to travel alongside their mothers, the herd continued northward.
Within hours of being born, calves become fast runners, and easily keep up with their
mothers.
If a mother and her calf become separated, the mother will spend hours looking for her
lost young.
Regardless of where calving occurs, caribou gather annually to feast on the abundance
of vegetation at their traditional calving grounds on the Refuge, later moving to coastal
areas to avoid pesky insects.
These areas constitute their summer range, where new calves are able to access nutritious
food and the entire herd can put on much-needed pre-winter weight.
Later in the year, the summer range becomes inhospitable due to harsh and windy weather,
prompting the caribou to return south for the winter.
The migration route taken by the caribou is very remote; therefore, researchers typically
do not monitor their entire journey, which consists of harsh terrain and rough river
crossings.
What scientists do know, however, is that while some caribou may occasionally be lost
to the elements along their journey from point A to point B, the species as a whole has survived
many years of seasonal migrations.
6.
ARCTIC TERN
The Arctic Tern has the longest known migration of any animal, traveling up to 71,000 kilometers
(44,117.355 miles) per year.
These birds can live to around 30 years old, and over their lifespan, this can add up to
2.4 million kilometers (1,491,290.861 miles).
Arctic Terns travel from Greenland and the Arctic, to Antarctica and back - basically,
from the top of the world to the bottom, and back again!!
The shortest distance between the bird’s two migration points is 19,000 kilometers
(12,000 miles).
This migration pattern means that the Arctic Tern sees two summers annually and more daylight
than any other animal.
In the late summer of 1982, scientists in the UK track an Arctic Tern chick prior to
what was presumably its first migration.
By October, it reached Melbourne Australia, meaning that it traveled a distance of 22,000
kilometers (14,000 miles) in just three months.
Several other studies have shown migrations of similar distances, leading researchers
to conclude that traveling this far is the norm for an Arctic Tern.
5.
HUMPBACK WHALE
Humpback whales embark upon one of the longest annual migrations of any mammal.
The average migration route of a humpback whale is some 5,000 kilometers (3,106.856
miles) long.
This species can be found in all of the world’s oceans.
Populations of humpback whales in the southern hemisphere spend time feeding in Antarctica
during the summer months.
Every year during late Fall, they migrate from here to their winter breeding and calving
grounds in warmer Pacific waters, returning south in the Spring.
Northern Pacific humpback whales migrate from the icy Alaskan waters during autumn to the
waters off Hawaii.
To reach their destination, the whales swim nonstop for six to eight weeks.
Mother whales who are nursing their calves arrive first, usually in late November.
Next, they are joined by adult male whales.
Finally, pregnant whales, who stayed behind to feed until the very last minute, join the
group.
While at their Hawaiian “winter home,” humpback whales breed, as well as nurture
their young.
Humpback whales were once an abundant species; however, by the mid-1800’s, they were all
but depleted due to hunting.
The species reached an all-time low population of less than 1,000 in 1965.
Since then, efforts have been being made to restore the humpback whale’s former numbers
by protecting some of their habitats and by the introduction of a worldwide ban on whale
hunting in 1986.
4.
MONARCH BUTTERFLY
Because monarch butterflies cannot survive the cold temperatures characteristic of a
typical North American winter, they travel south and west during the fall to access more
habitable temperatures.
Most migrations begin during October, but if the weather cools even sooner, the species
may depart sooner.
Typically, they spend the winter in southern California and Mexico - places where it is
warm year-round.
Migration routes are up to 3,000 miles long, and monarchs can travel between 50 and 100
miles per day.
Their journey takes up to two months to complete.
Monarch butterflies must return north during the spring because the plants their larvae
feed on do not grow in the areas where they spend the winter.
The traveling population usually arrives at their northern destinations in the United
States and parts of Canada sometime during June.
This species is the only butterfly known to make a two-way migration.
The migration length of the monarch butterfly is longer than its actual lifespan, meaning
that no single monarch butterfly completes the cycle.
During their time spent up north, two to three generations of monarchs are born and pass
away.
3.
DRAGONFLIES
Monarch butterflies aren’t the only insect whose migration cycle is longer than their
lifespan.
Dragonflies have the longest-known migration of any insect, and it takes up to four generations
to complete it.
According to a 2009 claim by biologist Charles Anderson, which was published in the Journal
of Tropical Ecology, millions of dragonflies make the annual trek from southern India to
Africa.
This migration is not only the longest insect migration, but the first among insects that
occurs across open ocean water.
Anderson first noticed the dragonflies passing through in 1983, the year he arrived in the
Maldives.
Their presence was peculiar, since the 1,200-island archipelago, which lies between 500 and 1000
kilometers (310.686-621.371 miles) from mainland India, almost completely lacks surface freshwater,
which dragonflies need to survive.
With a little more digging, Anderson was able to establish what seemed like a clear timeline
of north-to-south travel among the dragonflies.
The insects first arrived in the Maldives during October, and their presence peaked
between November and December.
Each wave of dragonflies stayed for no more than a few days.
Then, between April and June, they reappeared.
Later research showed that the dragonflies migrate up to 4,400 miles (7,081.114 km) through
the air without landing.
Not all dragonflies make the entire journey non-stop, however, and some take pit-stops
to lay eggs and breed along the way.
According to scientists, there are indicators that the dragonflies travel along with moisture,
which is a necessary component of their breeding environment.
2.
CHINOOK SALMON
This seemingly unexciting species of fish is actually pretty fascinating because it
swims 3,000 kilometers (1,864.114 miles) upstream to spawn, or lay eggs, where it was born.
The chinook salmon, also known as the king salmon, spring salmon, June hog, and blackmouth,
spends up to two years in freshwater after hatching.
During this time, they live primarily in freshwater bodies ranging from big rivers to small streams.
Then, the salmon migrates to the nutritionally rich waters of the Pacific, where it spends
between two and five years reaching its large size, feasting on prey like herring, squid,
and sand lice.
When it comes time to breed, this fish returns to its original birthplace.
The migration of the chinook salmon is short-lived, as the species is semelparous, which means
that they die after spawning just once.
Unfortunately, human activity has interfered with the thriving of the chinook salmon species,
much like it has with many other animals.
Juveniles and adults alike are often prevented from reaching their appropriate habitats due
to barriers such as road culverts and dams.
1.
THE RED CRAB OF CHRISTMAS ISLAND
Fourteen species of land crab can be found on Christmas Island, but of them, the red
crab is the most well-known.
Somewhere between 40 and 50 million red crabs dwell in shady areas throughout the island.
The crabs migrate to the coast together once annually to breed.
Their migration occurs at the beginning of the wet season and is also tied to the phases
of the moon, and usually occurs in October or November.
Males arrive before females, and the journey typically takes over a week total.
Once they arrive on shore, the males dig burrows, which they defend against one another.
Once the females arrive, couples mate near the burrows.
The males then return to the island’s forests, while the females remain in the burrows for
another few weeks, laying and incubating their eggs.
Females lay their eggs in the ocean at the high tide during the last quarter of the moon
- and us humans thought we were complicated!
The women’s work is done after that, and they return to the forest.
After hatching, the crab larvae spend between three and four weeks at sea.
Then, as juvenile crabs, they return to the land.
The migration of red crabs is so significant, many roads in Christmas Island are closed
or blocked to ensure their safety.
Thanks for watching!!
Aren’t these migrations impressive?!!
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See you next time!!
Bye!!