Do Commercial Butterfly Releases Pose a Threat to Wild Populations?
Butterlies bred in captivity for use in special events may threaten wild butterfly populations
At weddings all across the country, it is an increasingly common scene: As they leave the ceremony, the smiling newlyweds are suddenly surrounded by a fluttering cloud of butterflies released by guests. Although it may appear a touching and harmless gesture, some scientists say the practice of releasing mail-order butterflies has a dark side.
"The fad of tossing butterflies about as if they were mere ornaments is extremely worrisome to all who care about the natural occurrence and genetic integrity of our rich butterfly heritage," says Washington biologist Robert Pyle, author of the National Audubon Society Field Guide to North American Butterflies.
In a recent letter to the journal American Butterflies, Pyle and four other leading lepidopterists called for a ban on commercial butterfly releases. The scientists are concerned that such butterflies may spread parasites to wild populations. They also worry that shipping eastern and western monarch butterflies to the opposite sides of the Rocky Mountains could lead to genetic alterations in these distinct populations and could result in the creatures failing to find wintering grounds. And they are fearful that releasing butterflies outside their natural ranges can create a false picture of their true distributions.
But commercial butterfly suppliers deny that releases have an adverse impact. "I don´t send diseased butterflies out into the environment," says Bethany Homeyer, owner of Michael´s Fluttering Wings Butterfly Ranch in Texas. She notes that a disease could quickly spread and wipe out her business. "And I don´t ship eastern monarchs to western sites."
The U.S. Department of Agriculture (USDA), which regulates interstate butterfly transport, allows monarchs and eight other common native species of butterflies to be dispatched within their natural ranges. Overall statistics on the butterfly trade are not available. But individual companies report a surge in orders. Rick Mikula, a Pennsylvania dealer who pioneered the butterfly release wedding more than a decade ago, now books orders for 500 to 800 butterflies a week. Customers may spend as much as $100 per dozen for some species such as monarchs. Suppliers typically feed the butterflies with sugar water, pack them in envelopes and ship them overnight in padded boxes.
As butterfly commerce reaches new heights, some scientists are particularly concerned about the potential spread of Ophryocystis elektroscirrha, a parasite found in both wild and commercially raised monarchs. "We don´t know the degree to which this pathogen contributes to the mortality of wild butterflies," says biologist Lincoln Brower, a monarch expert at Sweet Briar College in Virginia. "However, we do know that it is highly infectious, debilitating and ultimately lethal. It is very insidious in laboratory stock because it doesn´t show up for several generations, so breeders may think they have clean stock and release diseased butterflies by mistake."
Butterfly suppliers say some opponents of the trade may be letting emotions get in the way. "Some people just don´t like the idea of butterflies being commercialized," says Sheri Moreau of The Butterfly Conservancy in California. "I estimate less than 40,000 artificially raised monarchs were released last year to join a monarch population of over 150 million--hardly a statistical blip in the total population."
Bruce Walsh, a specialist in theoretical population genetics at the University of Arizona, confirms that the relatively small number of butterflies released are incapable of altering the genetic makeup of wild populations. In addition, he says there is no evidence for a spread of diseases between the two populations. Brower disagrees, pointing to research showing that O. elektroscirrha is transmitted by monarchs during mating.
USDA senior entomologist Robert Flanders believes that most butterfly suppliers are conscientious about following federal and state guidelines for shipping. "The problem," he says, "is that there has never been such a massive movement of butterflies in the United States as is occuring now."
The controversy seems likely to continue as the popularity of butterfly releases grows. But there may be at least one positive outcome. "At the very least," says Flanders, "concerns about commercialization are generating new research to answer questions about the impact mass releases have on butterflies and their habitats."
Wisconsin writer Judith Kirkwood had no butterflies at her wedding.