Many monarch butterflies are bred in captivity and then released by enthusiasts in the summer and fall to increase their declining numbers. Enthusiasts hope that this will increase the number of monarchs moving south to Mexico or Southern California, as they traditionally do each winter in North America.
But there seems to be a catch.
Monarch butterflies born in captivity have signs of difficulty migrating south.
"These monarchs have been imprisoned and prevented from migrating for many generations, and they have lost their migration genetically ̵
For the study, lead author and Ph.D. The student Ayse Tenger-Trolander bought monarch butterflies from a commercial breeder and placed them in a garden on the roof of a building. Although the monarchs were in mesh cages, they were still exposed to natural light, temperature and humidity. After mating these butterflies, Tenger-Trolander collected the eggs and raised the offspring into adulthood.
Tenger-Trolander stuck these butterflies in an open metal cylinder , which served as a "flight simulator" to determine in which direction they would fly.
As a group, these monarchs – descendants of the butterflies bought by the commercial breeder – did not try to fly south.
In a second experiment, she took monarch butterflies caught in the wild and bred her offspring indoors. Even in the flight simulator, this group did not turn south.
"We know that there are many hobbyists and enthusiastic breeders trying to show their best attitude and avoid buying from commercial breeders," said Tenger-Trolander in the statement. "But there could be a problem with the way they are reared indoors."
The study found that "migratory behavior is remarkably sensitive to genetic alterations and environmental changes" and that monarch butterflies reared by commercial breeders and in captivity differ genetically from monarchs in the wild.
The captured monarchs had rounder forewings, similar to the forewings of monarchs who do not migrate.
"We can not point out a single genetic change that it did because there are many of them," Kronforst said. "But we think somewhere in the genome there are changes that have broken it."
The US Fish and Wildlife Service has considered adding monarch butterflies to the list of endangered species.