Transcontinental Monarch Butterfly Migration Mapped Across an Entire Breeding Season

For the first time in the history of monarch butterfly study, researchers have mapped the monarch migration pattern between Mexico and Canada across the continent over an entire breeding season.

The information could be used to assist with monarch conservation efforts as the regal butterflies face increasing threats from habitat loss and loss of food resources, according to the researchers behind the study.

Tyler Flockhart, a PhD student in University of Guelph Department of Integrative Biology and lead author of a paper on the Monarch mapping, said the study will "[tell] us where individuals go and where they're coming from."

The unprecedented monarch study traced successive generations of adult monarchs to their birthplaces between the southern United States and Ontario over a single breeding season.

Integrative Biologist Ryan Norris, also of University of Guelph, said before their study, scientists had only a rough idea of the monarchs' annual colonization patterns.

"You could have a monarch showing up in Ontario, but we didn't know exactly where it came from," he said.

Norris said tracking monarch migration patterns is vital to understanding why monarch populations are declining and predicting the effects on the insects of milkweed plant loss, habitat destruction and other factors.

According to Flockhart, in 2012 the smallest-ever population of monarchs were recorded in their Mexican overwintering grounds.

He said their numbers have been "declining steadily" and that typically monarchs show up in southern Ontario by June or July. This summer, few had been sighted here by the end of July.

"To lose monarchs would be a huge blow to the environment and to the public. People can easily identify monarchs," Flockhart said. "It might be the first butterfly they see or catch as a child, and it's often the first story they hear about how animals migrate."

Flockhart and his colleagues' research is published in the journal Proceedings of the Royal Society B.