Unravelling the annual cycle in a migratory animal: breeding-season habitat loss drives population declines of monarch butterflies

Flockhart, D. T. Tyler, Pichancourt, Jean-Baptiste, Norris, D. Ryan and Martin, Tara G. (2015) Unravelling the annual cycle in a migratory animal: breeding-season habitat loss drives population declines of monarch butterflies. Journal of Animal Ecology, 84 1: 155-165. doi:10.1111/1365-2656.12253


Author Flockhart, D. T. Tyler
Pichancourt, Jean-Baptiste
Norris, D. Ryan
Martin, Tara G.
Title Unravelling the annual cycle in a migratory animal: breeding-season habitat loss drives population declines of monarch butterflies
Journal name Journal of Animal Ecology   Check publisher's open access policy
ISSN 0021-8790
1365-2656
Publication date 2015-01
Year available 2014
Sub-type Article (original research)
DOI 10.1111/1365-2656.12253
Open Access Status
Volume 84
Issue 1
Start page 155
End page 165
Total pages 11
Place of publication Chichester, West Sussex, United Kingdom
Publisher Wiley-Blackwell Publishing
Collection year 2015
Language eng
Abstract Threats to migratory animals can occur at multiple periods of the annual cycle that are separated by thousands of kilometres and span international borders. Populations of the iconic monarch butterfly (Danaus plexippus) of eastern North America have declined over the last 21 years. Three hypotheses have been posed to explain the decline: habitat loss on the overwintering grounds in Mexico, habitat loss on the breeding grounds in the United States and Canada, and extreme weather events. Our objectives were to assess population viability, determine which life stage, season and geographical region are contributing the most to population dynamics and test the three hypotheses that explain the observed population decline. We developed a spatially structured, stochastic and density-dependent periodic projection matrix model that integrates patterns of migratory connectivity and demographic vital rates across the annual cycle. We used perturbation analysis to determine the sensitivity of population abundance to changes in vital rate among life stages, seasons and geographical regions. Next, we compared the singular effects of each threat to the full model where all factors operate concurrently. Finally, we generated predictions to assess the risk of host plant loss as a result of genetically modified crops on current and future monarch butterfly population size and extinction probability. Our year-round population model predicted population declines of 14% and a quasi-extinction probability (<1000 individuals) >5% within a century. Monarch abundance was more than four times more sensitive to perturbations of vital rates on the breeding grounds than on the wintering grounds. Simulations that considered only forest loss or climate change in Mexico predicted higher population sizes compared to milkweed declines on the breeding grounds. Our model predictions also suggest that mitigating the negative effects of genetically modified crops results in higher population size and lower extinction risk. Recent population declines stem from reduction in milkweed host plants in the United States that arise from increasing adoption of genetically modified crops and land-use change, not from climate change or degradation of forest habitats in Mexico. Therefore, reducing the negative effects of host plant loss on the breeding grounds is the top conservation priority to slow or halt future population declines of monarch butterflies in North America.
Keyword Agricultural intensification
Annual cycle
Conservation planning
Genetically modified organisms
Matrix modelling
Migratory connectivity
Transboundary conservation
Q-Index Code C1
Q-Index Status Confirmed Code
Institutional Status UQ
Additional Notes Published online ahead of print 25 June 2014.

Document type: Journal Article
Sub-type: Article (original research)
Collections: Faculty of Science Publications
Official 2015 Collection
 
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