Migration

he Monarch Butterfly (Danaus plexippus) is a widespread tropical insect that ranges as far north as Canada. It cannot withstand freezing winter temperatures nor can it last in the high extremes of summer’s heat. To survive, the Monarch travels to safe stayover sites that are neither too cold nor too warm in what may be the most unique migration in nature.

The Monarchs hatched from the matings at the Pacific Grove site are capable of mating as soon as they emerge from the crysalis. They fly north as the lands warm up, to Oregon. They lay their eggs for the next generation and die, having lived only around four to six weeks. The Oregon hatched Monarchs, capable of mating with a short life span will fly further north to Washington, lay eggs and die once more. The Washington generation moves the farthest north into Canada, where the last milkweed is growing, usually within 100 miles of the US-Canadian border. Here they lay the last eggs of the summer.

Why is this migration so unique?
In many species, such as birds and whales, the same individuals travel the same routes year after year. However, the monarchs that migrate to Pacific Grove have never been here before. In fact, it was the great-great-grandparents of these monarchs from Canada who left Pacific Grove four generations before!

Monarchs east of the Rocky Mountains spend the winters in high mountains in centeral Mexico.

Monarchs west of the Rocky Mountains come to Pacific Grove and several other locations on the central California coast. Recent research indicates that monarchs from Arizona also travel to California.

Overwintering sites are found from just north of the San Francisco Bay Area to as far south as San Diego and Baja, California. En route, they may travel as far as 2,500 miles, covering perhaps a hundred miles a day, and flying as high as 10,000 feet. This is a mighty achievement for a creature much smaller and more fragile than the tiniest bird!
How do they find their way?
Scientists think that the monarchs may rely on the Earth’s magnetic field, the position of the sun and the polorization of the sun’s rays. These butterflies, hatched around the beginning of September, on the most northern milkweeds in Canada, with nothing but instinct to guide them, take five to six weeks to travel to Pacific Grove.

We begin to see them arriving during the first two weeks of October. They go immediately to the locations in town where their ancestors were sheltered the previous year. It is a mystery how these new Monarchs know where they should spend the winter.

Life Cycle

After mating up to 3 times each, the male Monarch will die, and the female Monarch flies almost 100 miles to find milkweed.

A female Monarch is capable of laying hundreds of eggs and only deposits them on very toxic milkweed plants. She approaches new, tender milkweed plants and taps the top of each leaf to test the toxicity of the plant.

If it is strongly poisonous, she deposits a single egg on the underside of the leaf, moving on to test another leaf and lays a single egg under it as well. In this way, she guarantees that the eggcaterpillar that emerges will have plenty to eat, and it will be protected from predators by becoming toxic from eating the milkweed. This toxicity will continue through the entire metamorphisis, thus the adult butterflies are also poisonous, and thus protected from predators. Scientists are able to genetically trace the butterflies during migration by knowledge of the species of milkweed the butterfly fed upon as a caterpillar.

The newly hatched caterpillar (larva) immediately eats the eggshell from which it emerged, then voraciously feeds on the milkweed host plant for 10 to 20 days. During that time, the caterpillar must shed its yellow, black and white striped skin four times as it expands from 1/16th of an inch to about 2 inches in length, and increases its weight by a factor of 2,700 times.

After it has reached its full size, the caterpillar spins a sticky button called a cremaster on or near the milkweed and attaches to the button by its rear claspers, letting go with all its legs and hanging for about a day in a “J” shape. During this time many changes take place within the body of the catterpillar. Then the caterpillar sheds its skin for the fifth and last time, kicking the entire caterpillar body off (head, eyes, antennae, stripes and legs), revealing the chrysalis forming.

The chrysalis at first resembles a sticky, wet jellybean with yellow stripes. During the first hour, the stripes move upward and form a crown of gold buttons near the top and down a side seam. The hardening chrysalis looks like a jade jewel and hangs quietly for approximately 10 days. Slowly the chrysalis becomes more and more transparent until the orange and black pattern of the butterfly within is revealed. The butterfly is ready to emerge from its chrysalis.

As soon as the chrysalis splits open along the seam, a Monarch, with an enlarged abdomen and very crumpled wet wings, emerges. Immediately, the Monarch begins to pump fluid from its abdomen into the crumpled wings along all the black lines which become veins. This action causes the wings to fully expand and flatten until they are perfectly formed. The Monarch stays very still for approximately three hours to let its wings dry and harden. The butterfly is now a fully grown, adult Monarch.

Habitat Protection

We are extremely concerned about the need for further protection and enhancement of the dwindling resources in the monarchs’ overwintering habitats and the lack of available milkweed along the migration flyways.

Pacific Grove Monarch Conservancy is working to establish and promote restoration of the urban forests and microclimates of the Monarch Grove Sanctuary and Washington Park in Pacific Grove. Pine Pitch Canker disease has ravaged the Monterey Pine forest. The habitat in Pacific Grove has been made up traditionally of Monterey Pines, Eucalyptus, and Cypress. Massive plantings of Monterey Pine seedlings by volunteers has sadly been ineffective in establishing needed additions to the microclimate.

Local Monarch butterfly enthusiasts, gathered donations and installed dozens of temporary potted trees to mitigate the 2009 tree trimming. As a result, the Monarchs that arrived in Fall 2010 had a suitable microclimate to remain into the overwintering season. The 2010 population peaked at about 7,000, and the butterflies have persisted at the Sanctuary well into March.

As a result of the unfortunate 2009 trimming, attention  has been focused on the condition of the Sanctuary. In early 2011, Dr. Stuart Weiss presented a plan to restore the viability of the Monarch Grove Sanctuary (Management Plan for Monarch Grove Sanctuary: Site Assessment and Initial Recommendations).

Further recommendations were given following a March 11, 2011 meeting:March 11, 2011 site visit to Sanctuary notes by Stuart WeissOn March 31, 2011, some of the donated boxed trees (mostly Eucalyptus) were planted about 15 feet from the row of mature Eucalyptus along the Sanctuary’s South perimeter.
Dr. Stuart Weiss explains his 2011 plan to plant a second row of Eucalyptus trees at the monarchs’ favorite roosting site at the Sanctuary. A yellow flag marks the future site of the first tree.

Read an article by Kera Abraham in the Monterey County Weekly: “Operation Butterfly”

Read an article by Kera Abraham in the Monterey County Weekly: “Monarch Movement”

Read an article by Steve Chawkins in the L.A. Times: “Anger flutters over ‘Butterfly Town USA'”

Read a blog by Monte Sanford, Ph.D: “Habitat Restoration Lessons from Pacific Grove”

MONARCH GROVE SANCTUARY UPDATE

Following a very severe pruning of the Monarchs’ favorite spot — an amphitheater of Eucalyptus trees near the south end of the Monarch Grove Sanctuary — in late September/early October the Monarchs are in record-breaking low numbers.

Estimates in early to mid-November vary from 5 to 750, at a time that typically sees tens of thousands clustering. On December 5 2009, 989 Monarchs were counted in the Sanctuary. On December 11, 2009, there were 635. By the end of December, there were about 300, and in the first week of January, less than 10 were counted.

Mating Ceremony

In mid-Febuary (near Valentine’s Day), the first milkweeds of Spring break through the ground, awaking the hormones of the male Monarch butterflies who have been in diapause throughout the winter.

The male Monarch begins to create a sweet-smelling, musky perfume called pheromones which he stuffs into the “pockets” (two black dots) on the rear wings.

He then proceeds to chase the females in spirals up into the sky and zooms in front of the female he chooses as his mate, sprinkling her with his perfume. She is just dazzled and almost stops in mid-air, allowing him to grasp her with his feet. This, however, makes it impossible for either of them to fly, so they drift slowly to the ground. Here they proceed in what appears to be a wrestling match for 10 to 15 minutes, oblivious of their surroundings. Visitors to the Butterfy Grove gather to watch the mating spectacle and to cheer on the mating couple.

The female does not cooperate, so that it must be a healthy, virile male that overwhelms her, guaranteeing the best genetic chance for survival of the fittest. He tries to quiet her by stroking her face with his antennae and putting his head down next to hers, appearing to whisper sweet nothings in her ear.

He then stands on his head and attempts to flip her over his body. If successful, their abdomens are the aligned properly so that they can “make the connection.” The female becomes docile and folds her wings together. The male does a remarkable thing: he runs a few steps like a plane taking off, then lifts the female up under his body and begins to fly.

He carries his mate underneath him through the air to the tops of the trees where it will be the warmest. They stay together for many hours, during which time he creates a small pellet called a spermataphore contains lipids (their energy source) which he passes along with the sperm into the body of the female.

When the sun comes up the following morning, the female flies away to find milkweed, laying up to 400 eggs.

Ecosystem

First, each of the California habitats is within a mile of the ocean and has a pattern of morning fog to bring a drink to the Monarchs each morning. They must have water every day.

The butterflies only need nectar every four to five days, and we supply that with butterfly gardens which many local people have planted in yards around the perimeter of the habitat. We call it the “Hospitality Zone.” We have also planted a large number of nectar-source plants on the habitat property. Our butterflies do not have to go far to get a meal — we spoil them in Pacific Grove.

Other microclimate parameters necessary for the Monarch’s survival through the winter include a closed canopy of trees with a single opening to the sky to keep the temperature steady. The basic temperature throughout the winter is usually between 55 and 70 degrees. Anything colder than 55 degrees, the Monarchs cannot fly. Anything hotter than 75 degrees for a long period of time would cause the butterflies to be too active, using too much of their lipids to survive until spring.

The habitat must also contain a mid-range of trees to act as wind buffers and the Monarchs also need trees with greenery from 20′ to 40′ off the ground, so that they can thermoregulate by moving themselves higher or lower in clusters as they deem necessary. Most of the Californian habitats are 100% Eucalyptus trees, but the Monarchs in Pacific Grove have traditionally used Monterey Pine trees as well as Eucalyptus and Cypress trees.

Butterfly Parade

Since 1939, Pacific Grove has celebrated the return of the Monarch butterflies with a welcoming parade. The parade is held on a Saturday morning in early October — call the Pacific Grove Chamber of Commerce at (831) 373-3304 for the date —  and is comprised of all the elementary schoolchildren dressed in costumes and accompanied by the school bands.

The parade is lead by Kindergartners, dressed as Monarch butterflies, in costumes made in class. Grades 1-6 follow dressed as friends of the Monarchs such as caterpillars, flowers, trees, and many other imaginative critters.

The small-town charm of the parade is made even more touching by the fact that it has taken place for over 60 years, so many of the grandparents watching along the parade route were once little Monarchs marching in the parade themselves.

The parade begins at Robert Down School, goes down Fountain Avenue, turns at the main street, Lighthouse Avenue, loops around, and finishes at Robert Down School with a Butterfly Bazaar on the school grounds.