Late, Sparse Butterfly Migration Puzzles Scientists

Tom Harvey, 512-389-4453,

News Image Share on Facebook Share Release URL

Note: This item is more than 19 years old. Please take the publication date into consideration for any date references.

AUSTIN, Texas — Every year, all of the monarch butterflies east of the Rocky Mountains, millions of them, migrate south through Texas to winter in the same region in the mountains of Central Mexico. This year, scientists are seeing something unusual, and they’re asking citizens to help them understand it by reporting monarch sightings.

“Judging from past year’s experience, the majority of the monarch migrants should be well into Texas by now, but they’re not,” said Mike Quinn, an entomologist with the Texas Parks and Wildlife Department.

Quinn says some reports of substantial monarch numbers have come in from Texas locations such as Midland, east of Amarillo, north of Dallas, Belton, Abilene and especially along the Concho River near San Angelo. However, most observers report low butterfly numbers compared to previous years.

Chip Taylor of the Monarch Watch program based at the University of Kansas describes this year’s migration as unique. He has followed the migration for the past 16 years, and used these words to describe the 2004 fall migration, "…atypical, late, slow, sparse, and undefined. Over the last 13 years, the movement of monarchs each fall has shown that there is a distinct pattern to the migration such that we can predict when the migrants first start to move and when the leading edge of the migration will reach each latitude as it progresses southward. The data behind this statement is quite impressive, but the migration this year doesn’t really fit the pattern and has us scratching our heads.”

The next 10 days represent the last opportunity to assess the size of this migration before the butterflies all move into Mexico. Scientists are urging the public to help assess the strength of the monarch migration through Texas by reporting when, where and approximately how many monarchs they see this month. Quinn is asking people to send him reports by e-mail (, not by phone.

For more information on monarch butterflies, see the Monarch Watch Web site (