Mar. 11, 2005 Monarch butterflies in eastern North America have
one of the longest migrations of any species, with a survival-
of-the-fittest trek that can take them thousands of miles from
Canada to Central Mexico. A new Emory University study has found
that these journeys may be the key to maintaining healthy
monarch populations at a time when habitat loss and other
environmental issues could curb the ability of the butterflies
to make the trip. Emory researchers discovered that monarch
butterflies infected with a protozoan parasite flew slower,
tired faster and had to expend more energy flying than healthy
monarchs. These results, published in the March issue of Ecology
Letters, may explain why parasite burdens are much lower in
migratory monarch populations compared to year-round residents
-- an effect that possibly occurs in other migratory species as
well, explains Sonia Altizer, lead researcher of the study and
an assistant professor of environmental studies at Emory. "We
know that several species of bi