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Author Notes:

Email: saltizer@uga.edu

Conceived and designed the experiments: SA.

Performed the experiments: SA LW KH.

Analyzed the data: SA AKD JCdR.

Contributed reagents/materials/analysis tools: SA LW KH.

Wrote the paper: SA KH AKD JCdR LW.

We thank Rachel Rarick, Michael Maudsley, Adam Federman, Jeff Smith, Eduardo Rendon, and Isabella Ramirez for field assistance and Ernie Osburn, Samantha Burton and Michael Maudsley for laboratory assistance.

The authors have declared that no competing interests exist.

The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.


Research Funding:

This work was supported by a National Science Foundation (www.nsf.gov) grant (DEB-0643831) to SA and Environment Canada (www.ec.gc.ca/financement-funding/) operating grants to LIW and KAH.


  • Animal migration
  • Protozoan infections
  • Wings
  • Latitude
  • Moths and butterflies
  • Mexico
  • Parasitic diseases
  • Adults

Do Healthy Monarchs Migrate Farther? Tracking Natal Origins of Parasitized vs. Uninfected Monarch Butterflies Overwintering in Mexico


Journal Title:



Volume 10, Number 11


, Pages e0141371-e0141371

Type of Work:

Article | Final Publisher PDF


Long-distance migration can lower parasite prevalence if strenuous journeys remove infected animals from wild populations. We examined wild monarch butterflies (Danaus plexippus) to investigate the potential costs of the protozoan Ophryocystis elektroscirrha on migratory success. We collected monarchs from two wintering sites in central Mexico to compare infection status with hydrogen isotope (δ2H) measurements as an indicator of latitude of origin at the start of fall migration. On average, uninfected monarchs had lower δ2H values than parasitized butterflies, indicating that uninfected butterflies originated from more northerly latitudes and travelled farther distances to reach Mexico. Within the infected class, monarchs with higher quantitative spore loads originated from more southerly latitudes, indicating that heavily infected monarchs originating from farther north are less likely to reach Mexico. We ruled out the alternative explanation that lower latitudes give rise to more infected monarchs prior to the onset of migration using citizen science data to examine regional differences in parasite prevalence during the summer breeding season. We also found a positive association between monarch wing area and estimated distance flown. Collectively, these results emphasize that seasonal migrations can help lower infection levels in wild animal populations. Our findings, combined with recent declines in the numbers of migratory monarchs wintering in Mexico and observations of sedentary (winter breeding) monarch populations in the southern U.S., suggest that shifts from migratory to sedentary behavior will likely lead to greater infection prevalence for North American monarchs.

Copyright information:

© 2015 Altizer et al.

This is an Open Access work distributed under the terms of the Creative Commons Attribution 4.0 International License (http://creativecommons.org/licenses/by/4.0/).

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