anna skye harnsberger - monarchconservation.org€¦ · 25-11-2019  · • if the goal of...

Grassland patches surrounded by less grassland contain more monarch butterflies compared to patches surrounded by more grassland.

However, egg + larva abundance was most related to the density of milkweeds.

MONARCH BUTTERFLY LANDSCAPE ECOLOGY:Effects of landscape and local patch characteristics on monarch abundanceAnna Skye Harnsberger¹, Karen Oberhauser¹, Wayne Thogmartin², Chris Trosen³, Claudio Gratton¹¹University of Wisconsin-Madison, ²United States Geological Service, ³United States Fish & Wildlife Service

PROBLEM• Loss of milkweed from the landscape.• ~1.8bil stems needed to sustain the

eastern migratory monarch population.

HOWEVER• Need to know how to optimize habitat

restorations for monarchs.• Does surrounding landscape influence

abundance of monarchs at a site?• How densely should stems be planted?• How big should plantings be?• Are many nectar species are needed?

PREDICTION• Patches with less surrounding grassland

will have higher monarch abundances.• Small patches with higher milkweed

density and more nectar plant species will contain more monarchs.

APPROACH• Surveyed 60 WI sites 3x each; 2018-19.• Measured monarch abundance, patch

size, milkweed density, nectar plants, landscape-level grassland.

• Multiple regressions including yr, region.

Figure 1 | Map of survey sites in Wisconsin.

ResultsTable 1 | Results from multiple regression models showing significance of each factor to each monarch life stage response metric. Symbols represent positive (+), negative (-), p≤0.001 (***), p≤0.005 (**), p≤0.05 (*), & p≤0.1(†) associations, and higher numbers (↑).

Figure 2 | Component-residual plots of factors with significant associations to monarch abundance.

Conclusions• If the goal of restoration is to see adult

monarchs, it should be placed within a site with less surrounding grassland on a 10km scale, rather than more. More nectar species are better than fewer. High milkweed density is important.

• If the goal of restoration is monarch recruitment, it is most important to plant a high density of milkweed stems.

• Abundance within a patch is not well predicted by the size of the patch; thus, milkweed plantings of any size could be beneficial to the monarch population.

Next Steps• Create mixed-effect models, treating site

survey time (early, mid, late summer) as a random effect.

• Model selection.

Adu

lt m

onar

chs

(ave

rage

)co

mpo

nent

+ re

sidu

al

Landscape grassland (proportion grassland within 10km, excluding grassland within 1km, standardized)

Adu

lt m

onar

chs

(ave

rage

)co

mpo

nent

+ re

sidu

al

Adu

lt m

onar

chs

(ave

rage

)co

mpo

nent

+ re

sidu

al

Eggs

+ la

rvae

per

m² (

aver

age)

com

pone

nt +

resi

dual

Milkweed density(stems per m², standardized)

Milkweed density(stems per m², standardized)

Nectar plants(count, standardized)

A

BC

D

A B

C D

skye.harnsberger@wisc.edu

@LEPIDOPTERIST@GRATTONLAB