Long-Term Trends in Eastern North American Monarch Butterflies: A Collection of Studies Focusing on Spring, Summer, and Fall Dynamics:

Abstract

The monarch butterfly, Danaus plexippus (Nymphalidae, Danainae), is one of the most familiar and appreciated insects in North America and is an iconic symbol of insect conservation (Gustafsson et al. 2015); attention on this charismatic species has increased since declines of their Mexican overwintering colonies were reported (Brower et al. 2012). These declines are alarming, yet they may or may not be representative of the patterns for other phases of this species’ ontogeny or its phenology. The collection of articles in this special feature was produced by researchers associated with a variety of nation-wide citizen science projects that have been tracking monarchs for many years, with the overarching goal of identifying long-term trends in their abundance or distribution outside of the wintering period. The articles in this feature include: 1) a study that reports patterns of spring recolonization within the breeding range (Howard and Davis); 2) two articles that examined long-term changes in reproductive output (Stenoien et al., Nail et al.); 3) a paper that analyzes censuses of summer adult monarchs from two butterfly monitoring programs (Ries et al.); 4) two studies focusing on fall migration censuses (Badgett and Davis, Crewe and McCracken); and 5) a paper examining 18 yr of migration tagging and recovery data from one site (Steffy). The collective results of these studies should have a significant impact on our current understanding of eastern monarch population dynamics. For example, despite dramatic reductions in overwintering size, there has been no detectable change in the recolonization of the overall breeding range of monarchs in the past 18 yr (Howard and Davis), and at least one model suggests …