Summary of Available Data from the Monarch Overwintering Colonies in Central Mexico, 1976–1991

Open-File Report 2020-1150
Prepared in cooperation with the U.S. Fish and Wildlife Service
By: , and 



Historical estimates of the area occupied by overwintering Danaus plexippus (monarchs) in central Mexico (between winters of 1976 and 1991) were published in García-Serrano and others (2004) and more recently in Mawdsley and others (2020). Our primary objectives were to identify the specific data that informed those estimates and, importantly, determine the degree to which the reported estimates reflect the total size of the overwintering monarch population during that period. Understanding how historical estimates of the overwintering area relate to total population size is necessary to ensure that inferences about population abundance and temporal trends are reliable, particularly as the U.S. Fish and Wildlife Service is in the process of determining if the species should be listed under the U.S. Endangered Species Act.

Suggested Citation

Zylstra, E.R., Thogmartin, W.E., Ramírez, M.I., and Zipkin, E.F., 2020, Summary of available data from the monarch overwintering colonies in central Mexico, 1976–1991: U.S. Geological Survey Open-File Report 2020–1150, 10 p.,

ISSN: 2331-1258 (online)

Study Area

Table of Contents

  • Overview
  • Monarch Migratory Cycle and Overwintering Ecology
  • Data Collection at Overwintering Colonies, 1993–2019
  • Historical Data, 1976–1990
  • Inferences About Monarch Population Size and Trends
  • References Cited
Publication type Report
Publication Subtype USGS Numbered Series
Title Summary of available data from the monarch overwintering colonies in central Mexico, 1976–1991
Series title Open-File Report
Series number 2020-1150
DOI 10.3133/ofr20201150
Year Published 2021
Language English
Publisher U.S. Geological Survey
Publisher location Reston, VA
Contributing office(s) Upper Midwest Environmental Sciences Center
Description iii, 10 p.
Country Mexico
Online Only (Y/N) Y
Google Analytic Metrics Metrics page
Additional publication details