Ernest Williams, the Christian A. Johnson Excellence in Teaching Professor of Biology, published the lead article in the latest issue of the Journal of the Lepidopterists' Society 62(4):177-188. The article, "Monarch butterfly clusters provide microclimatic advantages during the overwintering season in Mexico," was coauthored by collaborators from Sweet Briar College and the Universidad Nacional Autonoma de Mexico and was based on field work in Mexico during February 2007 and January 2008.
The study documented the microclimatic buffering that takes place in the dense clusters of monarchs that form in their overwintering colonies on mountains of central Mexico. In the clusters, temperatures are a little warmer at night (reduces the likelihood of freezing) and a little cooler during the day (reduces lipid consumption), and the humidity is slightly higher at all times (reduces the likelihood of dessication). This study adds to our understanding of the suite of adaptations that enable monarchs to survive the winter.
