Tracking climate impacts on the migratory monarch butterfly

Abstract

Understanding the impacts of climate on migratory species is complicated by the fact that these species travel through several climates that may be changing in diverse ways throughout their complete migratory cycle. Most studies are not designed to tease out the direct and indirect effects of climate at various stages along the migration route. We assess the impacts of spring and summer climate conditions on breeding monarch butterflies, a species that completes its annual migration cycle over several generations. No single, broad-scale climate metric can explain summer breeding phenology or the substantial year-to-year fluctuations observed in population abundances. As such, we built a Poisson regression model to help explain annual arrival times and abundances in the Midwestern United States. We incorporated the climate conditions experienced both during a spring migration/breeding phase in Texas as well as during subsequent arrival and breeding during the main recruitment period in Ohio. Using data from a state-wide butterfly monitoring network in Ohio, our results suggest that climate acts in conflicting ways during the spring and summer seasons. High spring precipitation in Texas is associated with the largest annual population growth in Ohio and the earliest arrival to the summer breeding ground, as are intermediate spring temperatures in Texas. On the other hand, the timing of monarch arrivals to the summer breeding grounds is not affected by climate conditions within Ohio. Once in Ohio for summer breeding, precipitation has minimal impacts on overall abundances, whereas warmer summer temperatures are generally associated with the highest expected abundances, yet this effect is mitigated by the average seasonal temperature of each location in that the warmest sites receive no benefit of above average summer temperatures. Our results highlight the complex relationship between climate and performance for a migrating species and suggest that attempts to understand how monarchs will be affected by future climate conditions will be challenging.

Tracking multi-generational colonization of the breeding grounds by monarch butterflies in eastern North America

“…Monarch breeding distribution has been described by three non-mutually exclusive hypotheses (see the electronic supplementary material, table S1): (i) habitat suitability characterized by land cover (per cent trees, per cent herbaceous and per cent bare ground) and monthly normalized difference vegetation index (NDVI; [23,24]); (ii) geographical limits dictated by the timing and extent of migration characterized by latitude, longitude, altitude and slope [19,25,26]; and (iii) physiological constraints on development and movement imposed by weather conditions characterized by temperature and precipitation [19,25,27,28].…”

Understanding a migratory species in a changing world: climatic effects and demographic declines in the western monarch revealed by four decades of intensive monitoring

“…A further key contribution has come from the development of hierarchical models that can effectively estimate parameters (such as the influence of weather) across large numbers of species and locations (Royle and Dorazio 2008;Ponciano et al 2009;Congdon 2014;Nice et al 2014). A logical implementation of such models involves species that utilize large regions, and migratory species are of particular interest because of complex life cycles that integrate climatic variation across heterogeneous local climates (Zipkin et al 2012). A prominent migratory animal in North America is the monarch butterfly (Danaus plexippus).…”

Assessing Role of Major Drivers in Recent Decline of Monarch Butterfly Population in North America

“…A finding from this study is that high levels of precipitation and intermediate spring temperatures in Texas were correlated with the largest population abundance and arrival to summer breeding habitats in Ohio (Zipkin et al, 2012). However, the weather patterns within Ohio do not affect the arrival of monarchs to this location, and once in their summer breeding habitat, monarchs are minimally affected by precipitation (Zipkin et al, 2012). This suggests that monarchs are only affected by climatic conditions in certain points along their migratory path and only at specific times of the year.…”

“…To explain monarch summer breeding phenology and year-toyear fluctuations in population abundances, Zipkin et al (2012) built a Poisson regression model to estimate summer arrival times and resulting abundances in the United States Midwest. A finding from this study is that high levels of precipitation and intermediate spring temperatures in Texas were correlated with the largest population abundance and arrival to summer breeding habitats in Ohio (Zipkin et al, 2012). However, the weather patterns within Ohio do not affect the arrival of monarchs to this location, and once in their summer breeding habitat, monarchs are minimally affected by precipitation (Zipkin et al, 2012).…”