Monarch Butterfly Migration Path Mapped by Generations for First Time

Monarch butterflies have one of the most epic and chronicled migrations of the insect world. They journey thousands of miles each year between Mexico and Canada, wintering in the south before returning north once more. Until now, though, linking adult butterflies and their birthplaces during this complicated migration has remained near impossible. Yet scientists have now mapped this migration pattern over an entire breeding season, which may help them preserve this amazing creature.

Monarch butterflies are currently in decline. The vibrant insect is suffering from habitat destruction in addition to having to cope with insecticides and other chemicals in the environment. In particular, the loss of milkweed, the sole plant that Monarch larvae feed on, has drastically impacted butterfly populations.

Mapping the migration pattern of the monarch butterfly was no easy task. The researchers traced successive generations of monarchs to their birthplaces between the southern United States and Ontario over a single breeding season. More specifically, they used chemical markers in butterfly wings to match "waves" of insect generations with their birthplaces. Since milkweed's chemical signature varies from place to place, the scientist were able to analyze these chemical elements in order to map the butterflies. Before this effort, scientists only had a rough idea of these annual colonization patterns.

"This tells us where individuals go and where they're coming from," said Tyler Flockhart, one of the researchers, in a news release.

The migration itself spans hundreds of miles, but one of the key "stops" is in the U.S. Midwest. There, the loss of milkweed plants is negatively impacting butterfly populations. Of special concern is the planting of genetically modified corn and soy, which have affected butterfly survival.

"If habitats in the Midwest continue to decline, then monarchs will lose the ability to expand the breeding range, including those butterflies that end up here in Ontario," said Ryan Norris, one of the researchers, in a news release. "To lose monarchs would be a huge blow to the environment and to the public. People can easily identify monarchs. 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."

The findings are crucial for understanding the monarch migration and protecting these butterflies from future threats. Knowing exactly where these insects are born may help conservationists protect certain areas in order to bolster monarch populations.

The findings are published in the journal Proceedings of the Royal Society B: Biological Sciences.