WARM-WEATHERMIGRANTS
Lisa Crozier holds no doubt that warmer weather has led to her dis-
tinction of being the first person to discover a particular cold-sensitive
butterfly—the sachem skipper (Atalopedes campestris)—in the semi-
arid desert city of Yakima, located east of the Cascade Mountains in
south-central Washington. Hot, dry days and pleasantly cool nights
mark the summers of Yakima, population 72,000, and its nearby wine
country. While it is blessed with 300 days of sunshine, though, Yakima
faces cold winters with average minimum temperatures of 19.7°F.
Crozier says she figured it was just a matter of time before the lit-
tle cold-sensitive butterfly showed up in Yakima. Typically a southern
species, it had already migrated north into eastern Oregon and to a
cluster of small communities known as Tri-Cities, Washington, south-
east of Yakima, where its caterpillars struggled but hung on through
the winter.
She recognized the butterfly instantly when she saw it that day in
- “I was very excited,” says Crozier, who back then was a
University of Washington researcher studying the butterfly. “I would
just go every week to see if they were there. I had been doing it for a
year. So when they finally appeared, it was thrilling. Initially, I just
found one. And then about two weeks later, they appeared more con-
sistently in a whole bunch of different sites.”
“They look more like moths,” says Crozier, who found a sachem
skipper fluttering around the leafy alfalfa and shrubby rabbitbrush she
monitored. “So they aren’t like the glamorous butterflies that every-
body thinks about, but they are butterflies. This particular one is pretty
large. They’re fairly stocky. They’re extremelyfast fliers—that’s why
they’re called skippers. They fly in a straight line, almost like bees.”
Crozier theorizes that the year-round temperatures in Yakima had
warmed sufficiently to attract the winged colonizers. She believes a
warming climate “was definitely a prerequisite” for the butterfly’s
arrival. Her studies ruled out several other possible explanations. She
is quick to add that “there is neverjust one explanation.” Yet, she adds,
butterflies are “very sensitive to climate change.”
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