Sonia Altizer, an ecology professor in UGA’s Odum School of Ecology, was recently quoted by National Geographic about the migration of monarch butterflies to southwestern Mexico. As the temperature gets colder, monarch butterflies search for a safe place to spend the winter. There are several theories about why monarchs migrate and how they know where to go. Altizer suggests their immune systems are the reason.
“We think that migration weeds out the most heavily infected monarchs, removing them from the populations,” said Altizer, who has found that adult butterflies infected with a protozoan parasite can’t fly as well in lab tests and travel shorter distances in the wild.