- The Washington Times - Thursday, September 27, 2007

Robert Robbins, a research entomologist with the Smithsonian’s National Museum of Natural History, is spending this month watching his work fly in front of his eyes.

Mr. Robbins looks out his office window each day and sees monarch butterflies gathering before their annual migration.

Their trek is unlike any other in the animal kingdom. These orange-and-black butterflies prepare for winter by leaving their homes around the United States and Canada and heading south toward Mexico. There, they find their over-wintering spots, where they will stay until the weather to the north warms up.

The migration can be seen in the District area starting in August and running through October, or sometimes November if the weather stays warm.

“If you go to any of the butterfly gardens in the D.C. area, you’ll find them,” Mr. Robbins says.

Those who can grab a closer look at the butterflies can see that their abdomens are swollen with fat. That’s their equivalent of a full fuel tank.

“It takes a lot of energy to fly to Mexico,” Mr. Robbins says, energy provided by the flower nectar the butterflies eat in the weeks leading up to their journey. Monarch butterflies feast primarily on milkweed.

“There are other milkweed butterflies that do some migration, but nothing like the monarch,” he says.

The monarch butterflies that emerge in the late summer from their pupae, or chrysalides, aren’t the same ones that will come back north the next year. These butterflies do not mate or lay eggs until the spring. Their mission is to travel south, period.

The butterflies that begin the trek back north in the spring will be the children, and grandchildren, of the butterflies that land at the over-wintering regions. It can take up to five generations of butterflies to complete the entire cycle.

No butterfly that starts the journey completes the round trip.

Dick Walton, director of the Monarch Monitoring Project in Cape May, N.J., says the study of monarch butterflies took a huge leap forward in the mid-1970s when Canadian researcher Fred Urquhart solved “one of the great science mysteries of the 20th century.”

“The goal was to figure out where they were going,” Mr. Walton says of the butterflies’ path, which Mr. Urquhart did thanks to extensive tagging efforts. The tags, smaller than a thumbnail, are bent on top of the wing’s edge.

Not all of the mysteries surrounding the beautiful creatures have been solved.

“We’re still trying to get a handle on specific routes,” Mr. Walton says, adding that he thinks some over-wintering sites still elude researchers.

Not all monarch butterflies head south for the winter. Butterflies west of the Rockies stay relatively put, Mr. Walton says, while those east of the Rockies make the massive flight south.

Mr. Walton says the theory of how these butterflies made it to our shores involves a slow but steady march northward from Mexico in search of milkweed, the creature’s main food supply and its sole food source during its larvae stage.

“There’s always competition for resources,” he says.

Mr. Walton says last year’s monarch flight was particularly heavy. His group recorded butterflies traveling an average of 50 miles in a day.

Chip Taylor, director of Monarch Watch, says his group distributes more than 200,000 tags a year to track and study the butterflies.

“We learn a great deal about the migration, the timing and pace, how fast it moves. Then we learn a lot about the survival of the monarchs from different places around the country,” Mr. Taylor says.

His group gets fewer recovered butterflies along the Eastern coast, which possibly means some of the creatures get swept away by high winds, while others land on neighboring boats.

The monarch migration has gone on for thousands of years, Mr. Taylor says, but researchers still scratch their heads over parts of the process. How are these delicate creatures programmed to repeat the same movement pattern year after year? The butterflies lack a genetic map in their DNA that could explain such knowledge, Mr. Taylor says.

Whatever they”re doing, he says, they’re setting a different heading based on the latitudinal and longitudinal information available.

“They know where they are relative to the continent,” he says. “We don’t know how they get that information.”

Some bird species migrate for short distances, and an Australian moth does the same, but no other butterfly or insect engages in such a major migration as the monarch, he says.

The monarch’s migration is a thing of wonder, a process in which up to 100 million butterflies take part, according to Monarch Watch. However, some worry that their numbers may drop in the coming years.

“It’s a vulnerable population,” Mr. Taylor says. “They’re over-wintering in Mexico, but if you chop down all those trees there, this thing is going to collapse.”

Donita C. Cotter, a program specialist in the National Wildlife Refuge System’s division of natural resources, cites a number of reasons people should be worried about the majestic creatures.

Ms. Cotter says that, for starters, the butterflies’ life-giving food source is a weed, after all. Some areas of the world put the milkweed on their noxious weed list, and that causes people to spray them with herbicides to kill them. Plant pesticides can also directly kill the monarchs.

Urban development also puts the creatures in jeopardy. Mexicans deforest their lands for economic reasons, but in doing so, they can hurt the over-wintering spots upon which the butterflies depend.

Ms. Cotter calls the migration an “endangered natural phenomenon” in North America.

Those concerned about the monarch’s migration can do their own small part to protect the species, Mr. Taylor says.

Butterfly gardens offer small oases where the creatures can feast along their journey, says Mr. Taylor, who adds that this year portends to be about as strong for monarch sightings as was last year. The homeowner will get to see plenty of monarchs as a result, just not as many as at the roughly 11 to 14 known over-wintering sites. Those sites can have as many as 20 million monarch butterflies per acre.

Planting milkweed and other flowers that offer nectar to the butterflies isn’t complicated, he says.

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