WSU study charts migration of 15,000 Monarch butterflies

After five years and nearly 15,000 tagged butterflies, scientists now have proof that Monarch butterflies migrate from the Pacific Northwest to California in late summer and fall, a journey averaging nearly 500 miles.

Most of the tagging was done by citizen scientists and inmates from the Washington State Penitentiary in Walla Walla. The prisoners were carefully trained in raising, tagging and releasing Monarchs.

The findings were recently published in the Journal of the Lepidopterists’ Society.

WSU Entomology professor David James spearheaded the project, which took a massive amount of time and coordination to put together, ultimately involving hundreds of volunteers. The research was unfunded, which made the work by volunteers indispensable.

The paper covered the initial five years of the project, from 2012 to 2016. Participants tagged and released 13,778 Monarchs that were raised in captivity and tagged 875 wild Monarchs. More than one-third of the raised Monarchs were reared by inmates at Walla Walla, James said.

Butterflies were released from around Washington, Oregon, Idaho and British Columbia.

“On average, the butterflies averaged almost 40 miles of travel each day,” James said. “That’s pretty remarkable for such a small creature.”

Scientists suspect the Monarchs may ride warm air currents called thermals a few thousand feet up in the air, then use the strong upper-air currents to navigate, James said.

The longest recorded journey was from a butterfly released by James himself in Yakima that was recovered at Tecolote Canyon, near Goleta, Calif., a straight-line distance of 845 miles.