[Pollinator] "Can roadside habitat lead monarchs on a route to recovery?"

[Evan Cole]

Kasten, K., Stenoien, C., Caldwell, W. et al. 2016. Can roadside habitat
lead monarchs on a route to recovery? Journal of Insect Conservation
doi:10.1007/s10841-016-9938-y

http://link.springer.com/article/10.1007/s10841-016-9938-y



*Abstract*

The Eastern North American monarch butterfly population has severely
declined over the past decade. The decreasing availability of larval host
plants (milkweeds) due to the use of herbicide-tolerant crops has been
implicated in this decline. Roadsides could provide additional habitat for
monarchs. In this study we document the occurrence of milkweed and monarchs
on roadsides, and discuss whether roadsides are appropriate targets for
monarch habitat restoration. We sampled roadside rights-of-way in the Upper
Midwestern U.S. during the summer of 2015 to estimate the abundance,
distribution, and diversity of milkweeds and the extent to which monarchs
use these milkweeds. We then compared monarch densities in roadsides to
other habitat types and modelled immature monarch densities based on
several site characteristics. Our findings suggest that roadsides have
conservation potential for monarchs, especially when other habitat is
scarce and if wildlife-friendly management practices are enacted. Milkweeds
were found on ~60% of roadside transects. *Asclepias syriaca* was the most
common of the seven species encountered, occurring on 97% of transects with
milkweed. Immature monarchs were observed in roadsides, but in lower
densities than other habitats during the same time period. At lower
milkweed densities, immature monarch density per unit area is positively
correlated with milkweed density. However, milkweed density weakens as a
predictor of immature monarch density over ~0.6 plants per m2, possibly
indicating a saturation effect.





Evan Cole

Program and Development Associate

Pollinator Partnership

423 Washington Street, 5th Floor

San Francisco, CA 94111

e:  ec at pollinator.org

w:  www.pollinator.org

p:  415.362.1137

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