Density estimates of monarch butterflies overwintering in central Mexico
Given the rapid population decline and recent petition for listing of the monarch butterfly (Danaus plexippus L.) under the Endangered Species Act, an accurate estimate of the Eastern, migratory population size is needed. Because of difficulty in counting individual monarchs, the number of hectares...
| Main Authors: | , , , , , , , , |
|---|---|
| Format: | Article |
| Language: | English |
| Published: |
PeerJ Inc.
2017-04-01
|
| Series: | PeerJ |
| Subjects: | |
| Online Access: | https://peerj.com/articles/3221.pdf |
| _version_ | 1797420181744517120 |
|---|---|
| author | Wayne E. Thogmartin Jay E. Diffendorfer Laura López-Hoffman Karen Oberhauser John Pleasants Brice X. Semmens Darius Semmens Orley R. Taylor Ruscena Wiederholt |
| author_facet | Wayne E. Thogmartin Jay E. Diffendorfer Laura López-Hoffman Karen Oberhauser John Pleasants Brice X. Semmens Darius Semmens Orley R. Taylor Ruscena Wiederholt |
| author_sort | Wayne E. Thogmartin |
| collection | DOAJ |
| description | Given the rapid population decline and recent petition for listing of the monarch butterfly (Danaus plexippus L.) under the Endangered Species Act, an accurate estimate of the Eastern, migratory population size is needed. Because of difficulty in counting individual monarchs, the number of hectares occupied by monarchs in the overwintering area is commonly used as a proxy for population size, which is then multiplied by the density of individuals per hectare to estimate population size. There is, however, considerable variation in published estimates of overwintering density, ranging from 6.9–60.9 million ha−1. We develop a probability distribution for overwinter density of monarch butterflies from six published density estimates. The mean density among the mixture of the six published estimates was ∼27.9 million butterflies ha−1 (95% CI [2.4–80.7] million ha−1); the mixture distribution is approximately log-normal, and as such is better represented by the median (21.1 million butterflies ha−1). Based upon assumptions regarding the number of milkweed needed to support monarchs, the amount of milkweed (Asclepias spp.) lost (0.86 billion stems) in the northern US plus the amount of milkweed remaining (1.34 billion stems), we estimate >1.8 billion stems is needed to return monarchs to an average population size of 6 ha. Considerable uncertainty exists in this required amount of milkweed because of the considerable uncertainty occurring in overwinter density estimates. Nevertheless, the estimate is on the same order as other published estimates. The studies included in our synthesis differ substantially by year, location, method, and measures of precision. A better understanding of the factors influencing overwintering density across space and time would be valuable for increasing the precision of conservation recommendations. |
| first_indexed | 2024-03-09T06:58:56Z |
| format | Article |
| id | doaj.art-334c1d85c5504a419feba35a9609147c |
| institution | Directory Open Access Journal |
| issn | 2167-8359 |
| language | English |
| last_indexed | 2024-03-09T06:58:56Z |
| publishDate | 2017-04-01 |
| publisher | PeerJ Inc. |
| record_format | Article |
| series | PeerJ |
| spelling | doaj.art-334c1d85c5504a419feba35a9609147c2023-12-03T09:57:26ZengPeerJ Inc.PeerJ2167-83592017-04-015e322110.7717/peerj.3221Density estimates of monarch butterflies overwintering in central MexicoWayne E. Thogmartin0Jay E. Diffendorfer1Laura López-Hoffman2Karen Oberhauser3John Pleasants4Brice X. Semmens5Darius Semmens6Orley R. Taylor7Ruscena Wiederholt8Upper Midwest Environmental Sciences Center, US Geological Survey, La Crosse, WI, USAGeosciences and Environmental Change Science Center, US Geological Survey, Lakewood, CO, USASchool of Natural Resources and the Environment and Udall Center for Studies in Public Policy, University of Arizona, Tucson, AZ, USADepartment of Fisheries, Wildlife and Conservation Biology, University of Minnesota, St. Paul, MN, USADepartment of Ecology, Evolution, and Organismal Biology, Iowa State University, Ames, IA, USAScripps Institution of Oceanography, University of California, San Diego, La Jolla, CA, USAGeosciences and Environmental Change Science Center, US Geological Survey, Lakewood, CO, USADepartment of Ecology and Evolutionary Biology, University of Kansas, Lawrence, KS, USAEverglades Foundation, Palmetto Bay, FL, USAGiven the rapid population decline and recent petition for listing of the monarch butterfly (Danaus plexippus L.) under the Endangered Species Act, an accurate estimate of the Eastern, migratory population size is needed. Because of difficulty in counting individual monarchs, the number of hectares occupied by monarchs in the overwintering area is commonly used as a proxy for population size, which is then multiplied by the density of individuals per hectare to estimate population size. There is, however, considerable variation in published estimates of overwintering density, ranging from 6.9–60.9 million ha−1. We develop a probability distribution for overwinter density of monarch butterflies from six published density estimates. The mean density among the mixture of the six published estimates was ∼27.9 million butterflies ha−1 (95% CI [2.4–80.7] million ha−1); the mixture distribution is approximately log-normal, and as such is better represented by the median (21.1 million butterflies ha−1). Based upon assumptions regarding the number of milkweed needed to support monarchs, the amount of milkweed (Asclepias spp.) lost (0.86 billion stems) in the northern US plus the amount of milkweed remaining (1.34 billion stems), we estimate >1.8 billion stems is needed to return monarchs to an average population size of 6 ha. Considerable uncertainty exists in this required amount of milkweed because of the considerable uncertainty occurring in overwinter density estimates. Nevertheless, the estimate is on the same order as other published estimates. The studies included in our synthesis differ substantially by year, location, method, and measures of precision. A better understanding of the factors influencing overwintering density across space and time would be valuable for increasing the precision of conservation recommendations.https://peerj.com/articles/3221.pdfMixture distributionMonarch butterflyUncertainty modelingDanaus plexxipusDensity estimation |
| spellingShingle | Wayne E. Thogmartin Jay E. Diffendorfer Laura López-Hoffman Karen Oberhauser John Pleasants Brice X. Semmens Darius Semmens Orley R. Taylor Ruscena Wiederholt Density estimates of monarch butterflies overwintering in central Mexico PeerJ Mixture distribution Monarch butterfly Uncertainty modeling Danaus plexxipus Density estimation |
| title | Density estimates of monarch butterflies overwintering in central Mexico |
| title_full | Density estimates of monarch butterflies overwintering in central Mexico |
| title_fullStr | Density estimates of monarch butterflies overwintering in central Mexico |
| title_full_unstemmed | Density estimates of monarch butterflies overwintering in central Mexico |
| title_short | Density estimates of monarch butterflies overwintering in central Mexico |
| title_sort | density estimates of monarch butterflies overwintering in central mexico |
| topic | Mixture distribution Monarch butterfly Uncertainty modeling Danaus plexxipus Density estimation |
| url | https://peerj.com/articles/3221.pdf |
| work_keys_str_mv | AT wayneethogmartin densityestimatesofmonarchbutterfliesoverwinteringincentralmexico AT jayediffendorfer densityestimatesofmonarchbutterfliesoverwinteringincentralmexico AT lauralopezhoffman densityestimatesofmonarchbutterfliesoverwinteringincentralmexico AT karenoberhauser densityestimatesofmonarchbutterfliesoverwinteringincentralmexico AT johnpleasants densityestimatesofmonarchbutterfliesoverwinteringincentralmexico AT bricexsemmens densityestimatesofmonarchbutterfliesoverwinteringincentralmexico AT dariussemmens densityestimatesofmonarchbutterfliesoverwinteringincentralmexico AT orleyrtaylor densityestimatesofmonarchbutterfliesoverwinteringincentralmexico AT ruscenawiederholt densityestimatesofmonarchbutterfliesoverwinteringincentralmexico |