How long does the generation that migrates south live? what do they do once they migrate?

Inhaltsverzeichnis Show

What is so special about the Monarch butterfly?
The Magnificent Migration of Monarch Butterflies & How a Super Generation Makes it Happen
By Josie Knuth, Marketing & Communications Intern
WINTER HOLIDAY IN MEXICO
PREPARING TO JOURNEY NORTH
THE ULTIMATE RELAY TEAM
SUPER GENERATION IS BORN
TINY NAVIGATION SYSTEMS
FEASTING ON MILKWEED
How long do migrating monarchs live?
What generation of monarchs migrate?
Do monarchs return to where they were born?
What generation of monarchs migrate to Mexico?

The Monarch Grove at Pismo State Beach is publicly owned assuring its protection into the foreseeable future. Sites on privately owned land may not be as safe since development is reducing preserved space at an alarming rate. Although the Monarch Butterfly is not now an endangered species, biologists are beginning to worry about the survival of this amazing insect. Pismo State Beach is one of the largest monarch groves in the United States. The butterflies that come here are part of an ongoing study. A tagging program is helping scientists discover more about life patterns of the Monarchs. Monarch clusters, though in fewer numbers, are found throughout coastal San Luis Obispo County.

What is so special about the Monarch butterfly?

Along with the astonishing numbers found at over wintering sites along the California coast, even more astonishing is the story of how they got here. Two populations of Monarch butterflies call the United States home. The group living east of the Rocky Mountains migrates south to spend the winter in Mexico. Those living west of the Rockies migrate to the coast of central and southern California. Migration is not an uncommon phenomenon. So, what is so unusual about the Monarch butterfly migration? Let’s follow them. The western Monarchs’ summer range extends from the Rockies to the Pacific Ocean and north as far as southern Canada. In October, as colder weather approaches, the butterflies instinctively know they must fly south to escape the freezing temperatures. Some have to fly over 1,000 miles. The journey is hazardous and many never make it. By November, most are sheltering in trees stretching from the San Francisco Bay Area south to San Diego. Pismo State Beach hosts one of the largest over wintering congregations, varying in numbers from 20,000 to 200,000. The winter monarchs live about six to eight months. On sunny winter days they will fly away from the sheltering trees, searching for nourishment in flower nectar and water to drink. In late February, as the weather turns warm, the great migration north begins.

After a flurry of mating, the female Monarchs fly north seeking milkweed plants where they must lay their eggs. Their job done, the winter Monarchs soon die. It would seem as though the migration had come to a halt before it even got under way. This though, is

where it gets interesting. The eggs hatch after a few days and the tiny larvae voraciously begin eating milkweed leaves day and night. Milkweed is the only food the larva can eat but it eats enough to increase its weight 2,700 times in just two weeks. This is equivalent to a human baby growing to the size of a gray whale in just two weeks! Once it’s eaten its fill, the fullgrown caterpillar attaches itself to a solid object, sheds its skin, and forms a hard,

green and gold colored outer skin called a chrysalis. For the next two weeks inside the chrysalis, the fat, striped caterpillar rearranges its body’s molecules and then emerges as a beautiful orange and black Monarch butterfly. The new summer Monarchs continue to fly farther north, mating, laying their eggs on milkweed, then dying. The summer monarchs only live about 6–8 weeks but each new generation flies farther and farther north, following the growing milkweed. This cycle repeats itself 4–5 times throughout the summer. It is unknown how the successive generations of butterflies inherit the information needed to return to the over wintering sites but with the shortening days of October, the new winter generation of Monarchs does not mate and die but instead migrates south. How do they know where to go? Experience the mystery of these butterflies, enjoy their beauty, and learn more about their fascinating behavior at Pismo State Beach.

The Magnificent Migration of Monarch Butterflies & How a Super Generation Makes it Happen

By Josie Knuth, Marketing & Communications Intern

No migration compares to that of the small, black and orange creature you see fluttering through your neighborhood in summer.

When you think about migration, you might describe how birds fly south for the winter and return when temperatures warm up again. For a monarch, migration is much more complex and requires multiple generations to complete its journey, including one very special generation known as the super generation.

The monarch is the only butterfly known to make a two-way migration like birds typically do. Monarch larvae, pupae, and adults can’t survive cold temperatures so they fly as far as 3,000 miles to reach a habitable climate for the winter months.

PC: John Oates Photography

As you can imagine, this journey is no easy task for the monarch who weighs less than a gram and has a wingspan of just 3 to 4 inches. Nevertheless, these tiny creatures travel up to 50 miles a day, flying as high as one mile in the sky… Incredible!

Take a closer look at the migration of the monarch butterfly and you may never look at them the same way again!

WINTER HOLIDAY IN MEXICO

The super generation of monarchs overwinters in the mountain ranges of Central Mexico, a location that offers the perfect climate. The humidity of this area keeps them from drying out and helps conserve their energy.

From October to late March, several hundred thousands of monarchs gather in the towering treetops of the oyamel fir forests. They return to these same mountain ranges each year, creating one of the most astonishing sights you will ever see.

Monarchs live off stored energy for several months until their internal seasonal clock tells them it’s time to leave.

PREPARING TO JOURNEY NORTH

Once a monarch’s internal clock tells them it’s time to head north, they begin releasing a certain hormone and they become reproductive. At this time, female monarchs lay their eggs and soon every butterfly that survived the winter dies.

Monarch caterpillar on leaf

Eventually these eggs hatch into a typical adult monarch and they begin to fly north. Regular generations of monarchs only live 2-6 weeks so it often takes 4-5 generations of monarchs to make the trip north.

THE ULTIMATE RELAY TEAM

What makes the monarch migration so unique is that it requires an intergenerational relay team to complete its annual migration to Mexico.

During the migration north, the monarch flies, mates, lays eggs, and ultimately dies as it passes the baton to the next generation. It’s up to their children and grandchildren to continue the journey.

By August, third or fourth generations of monarchs will reach their northernmost destination in the United States and Canada, including Wisconsin! Then as late summer arrives, shorter days and cooler temperatures cue the female monarch to lay a special egg.

SUPER GENERATION IS BORN

These caterpillars grow up to be very different from previous generations. The absence of an age inducing hormone will allow them to live 8 times longer and fly 10 times farther than their parents and great-grandparents.

Now it’s up to this super generation of monarchs to make the trip from northernmost parts of North America to Central Mexico.

So how does a butterfly who was born in northern parts of North America know how to navigate all the way to a place it’s never been before?

In order to navigate the long journey to Mexico, monarchs use the tiny solar compasses in their pin-sized brains.

Monarchs navigate by reading the horizontal position of the sun and by using an internal clock. Since monarchs don’t carry a wrist watch, they rely on their small antennae to tell them what time of day it is. Factoring both the location of the sun in the sky and the time on their antennae clock, monarchs can point themselves in the right direction. On cloudy days the monarch’s eyes have special cells that can find the sun using polarized light.

The super generation completes the longest ‘leg’ of the relay by mid to late November and overwinter in the mountains of Central Mexico.

FEASTING ON MILKWEED

Milkweed is essential to the survival of monarchs. Female monarchs lay eggs on milkweed plants and monarch caterpillars feed on milkweed. In fact, milkweed is the only thing caterpillars eat, and they eat a lot of it!

Monarch caterpillars eat and eat until they grow so much they shed their skin. They’ll do this 4 to 5 times before cozying up in their chrysalises.

Support monarch populations and their magnificent migration by planting milkweed! Don’t know what to plant in your region? Check out this helpful handout for information about selecting and finding milkweed plants for your garden or landscape.

Want to learn more about how you can help support monarchs? Check out these resources:

SAFE Monarch
Monarch Joint Venture
JourneyNorth

Sources

fs.fed.us
Unraveling the Great Butterfly Migration Mystery

How long do migrating monarchs live?

Most monarch butterflies live for 5 weeks, except for the generation born at the end of summer. These butterflies will live up to 8 months as they fly back to their wintering grounds in Central and South America, where they stay until the following spring.

What generation of monarchs migrate?

Generation 1 monarchs are the offspring of the monarchs who overwintered in Mexico. Each successive generation travels farther north. It will take 3-4 generations to reach the northern United States and Canada.

Do monarchs return to where they were born?

Successful migrating monarchs will live between 6 to 9 months and reproduce and die in the southern U.S. in the spring. Their offspring then carry on their migration north. Therefore, individual monarchs do not make it back to their original starting place.

What generation of monarchs migrate to Mexico?

Some generation 3 individuals emerge early enough to reproduce in the northern part of their breeding range or after moving south (see immature distribution map). However, Generation 3 individuals that emerge late in August will undergo diapause and migrate to Mexico, as will most Generation 4 individuals.