Monarchs taking a shorter trip, migrating to Florida instead of Mexico

Migrating monarch butterflies might be stopping in Florida instead of making their way to Mexico because of their body condition, according to study published in the journal Animal Migration.

According to Hannah Vander Zanden, a biology professor at the University of Florida and one of the lead authors on the study, a lack of fat stores and resources might be causing butterflies to stop early.

She said lately they're seeing migratory monarchs in Florida, where the climate is "conducive" for letting monarchs stay year-round.

"We assumed there's not a lot of mixing between resident and migratory populations," said Vander Zanden. "We had the ability to look more at the region [of origin] and found some are coming from as far north as Canada."

She said the eastern population of monarch butterflies are mostly migratory. At Point Pelee National Park, thousands of monarch butterflies stop each year. Vander Zanden said those butterflies are usually on their way to Mexico.

The way researchers tracked the butterfly's origin was through a local signal integrated by butterflies when they eat milkweed as caterpillars.

Other reasons for butterflies not moving all the way down south include random chance, being displaced by weather or not having good navigation skills, said Vander Zanden.

However, she said butterflies sensing their body condition won't make it all the way to Mexico is a more likely factor.

Even though the study can help explain why monarch populations in Mexico are on the decline, Vander Zanden said it's not the whole story.

"Habitat loss in their summering ground, or factors during migration or in their wintering site — there are many different ways they can encounter threats."