Scientist Reports Firsthand on Monarchs' Migration Route

A Monarch butterfly rests on a rope, which is tied to a gas production platform in the Gulf of Mexico 70 miles south of Cameron.

For example, the Louisiana Department of Wildlife and Fisheries and many sports fishermen have long attested that the submerged infrastructures of offshore drilling rigs and production platforms attract both quantities and varieties of fish by acting as artificial reefs.

Ornithologists - bird scientists - also readily acknowledge that many species of migratory birds regularly take advantage of the offshore structures for temporary refuge during inclement weather.

Small particles of the mineral magnetite (shown above) are incorporated into the body of the monarch butterfly. Scientists believe that the substance allows monarchs to orient to the earth's natural magnetic fields in order to migrate south in the fall and north in the spring.

Now, a third biological group can be added to the growing roster of beneficiaries of offshore oil production: butterflies. To be precise, monarch butterflies.

For the past four years, with cooperation from UNOCAL Corporation and Petroleum Helicopters, Inc., I have been able to amass substantial evidence that myriads of brightly colored range-and-black monarch butterflies descend temporarily upon various offshore structures each October and, to a lesser degree, each March.

Although this documentation has proven to be a showcase phenomenon itself, analysis of the pinpoint data reveals an even more noteworthy conclusion: the existence of a consistent and unmistakable over-water flyway approximately 90 to 100 miles wide and 400 miles long between the southwest coast of Louisiana and the northeast coast of Tamaulipas, Mexico.

Small adhesive tags are used to track migrating monarchs. Information gathered from tagging programs so far indicates that monarchs can fly a straight-line distance of over 2,000 miles.

The new route, although suspected by some scientists, was previously undocumented. In the past, most scientists concluded that monarchs tend to avoid large bodies of water, preferring to fly instead above land from their summer breeding grounds in Canada and the United States to their overwintering grounds in the cool mountain forests of central Mexico. I theorize that the highway in the sky, now christened the monarch "Trans-Gulf Express," allows the migrating insects to shorten significantly both in time and mileage their fall and spring journeys.

Just how airborne monarchs locate the offshore structures remains a mystery. Empirical data, however, suggest that color and magnetism play key roles. Past research has proven that monarchs are extremely sensitive to color, especially yellow, and that their bodies contain magnetite, a so-called biosynthetic compass empowering the insects to orient to the earth's natural geomagnetism.

Since more than 90 percent of the offshore sightings involve structures painted bright yellow, and since these facilities generate substantial electromagnetic fields, I theorize that the insects' genetic programs are fooled by false readings from their internal compasses.

With more than 3,000 man-made structures fanning out nearly 150 miles south of the Louisiana coast, monarchs drift farther and farther off course. And once over the water, the butterflies mistake the colorful protuberances for patches of wildflowers, a potential source of nectar and energy.

Butterfly scientist Dr. Gary Noel Ross, author of this article, tags a monarch. Since butterflies live less than one year, new monarchs have to be tagged each year.

They then descend to refuel. But finding nothing for sustenance, they simply take advantage of the opportunity to rest, often through the night, on the dangling ropes, metal gratings, and heavy machinery.

Eventually, however, the migratory imperative becomes too compelling. The wayward butterflies abandon the fortuitous "pit stops" and continue flying for another 10 to 13 hours until landfall, when adequate sources of food and water are available and when their internal guidance systems are once again put on track.

To be sure, the final story of the "Trans-Gulf Express" has yet to be told. Although I am tantalized by the possibility that the petroleum industry may have inadvertently sparked the evolution of the flyway, I find that concept difficult to accept, acknowledging that oil exploration of the Gulf of Mexico dates back only 40 to 50 years.

I think the probable truth is that the monarchs are simply exploiting man in much the same way as fish and migratory birds do. I am convinced, though, that the role of the offshore structures should not be taken lightly. Since the over-water route probably enhances survival potential for the monarch as a species, I theorize that the "Trans-Gulf Express," which may have been initiated in some long-forgotten time and by only a few aberrant wanderers, is now being continually reinforced - and perhaps even expanded each year - because of the presence of the petroleum industry in the Gulf. Time will tell.

So, who said that oil, water, and wildlife can't coexist?

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