Mystery of the Monarch butterflies solved | WWF

Mystery of the Monarch butterflies solved

Posted on
11 May 2001
Cerro San Andres, Mexico - The great majority of the gorgeous Monarchs gather in huge colonies within the protected Monarch Butterfly Biosphere Reserve in Michoacan, Mexico, where tourists gawk at trees dripping with butterflies and the air is thick with the flying insects. A few relatively small colonies gather outside the reserve, such as on San Andres mountain, which was not included when the reserve was expanded by presidential decree last year to 133,400 acres (54,000 ha) from 39,540 acres (16,000 ha).

The butterflies' deaths created alarm among local environmentalists and the tourist industry and questions for scientists about what exactly caused the phenomenon. The official report given by PROFEPA (the Environmental Enforcement Agency) determined that the butterflies died from the cold. According to their report, a total of 2,291,340 butterflies out of a population of 28,340,000 died this year. In San Andres 326,370 butterflies died, representing 29.7% of that colony.

After PROFEPA collected samples of the dead butterflies and had them analyzed in independent chemical laboratories, no chemical evidence of insecticides was found.

"Having talked with associates who contacted local citizens in the butterfly areas, and with PROFEPA, we have come to the conclusion that the most reasonable explanation of the mortality is that it was caused by severe winter weather, exacerbated by the forest thinning," says Monica Missrie, coordinator of the Monarch butterfly project at WWF's Mexico office.

A PROFEPA scientist, Jesus Cerecero, says it was clear "there is not the vegetation cover they need. For a lot of reasons the optimum conditions for butterflies do not exist."

Missrie says logging control was key in the area. "The authorities need to get their act together," she says. "In San Andres they have been begging the government to help them with illegal logging. PROFEPA are the ones who should be patrolling the area, and they don't have enough resources."

Maravatio Mayor Jose Jaime Hinojosa hopes the discovery of the mass butterfly deaths will prod authorities to declare the area a reserve and help him control logging there. "We want the authorities to declare this a reserve and stop the logging. For me it is even more serious if they died because of a lack of trees rather than because of a fumigation," Hinojosa says.

Logging is a major industry in an area of dramatic mountain ranges rising above rich fields of corn and vegetables. Trucks loaded with enormous trunks and wooden furniture bustle along the highways and every few miles there is a sawmill. Hinojosa says even owners of forest property are begging for protection because clandestine loggers are stealing their wood. They hope environmental programmes will compensate them for lost logging rights if a reserve is created. The justice system had to back up the police actions against loggers, Hinojosa says. "As municipal president I have stopped many logging trucks," he says. "I take them to the prosecutor's office and two to three hours later they are set free."

For more information contact: Monica Missrie, Coordinator Monarch butterfly project MMissrie@wwfnet.org