During their annual migration to wintering sites in Mexico, monarch butterflies encounter dangers ranging from cars and trucks to storms, droughts and predators. A study led by ecologists at the University of Georgia has found evidence that these iconic insects might be facing a new challenge.
With migration patterns of many species changing in response to human activities, some monarchs have started to stay put and breed throughout the fall and winter -- but at a cost. Resident colonies of monarch butterflies that breed year-round suffer extremely high rates of parasitism. Migrants passing through areas with resident monarchs can also be exposed to high levels of disease, and might even stop migrating themselves and stay at the resident sites. Read more about this study at Science Daily.