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Implications of Beetle Killed
Lodgepole Pine Effects on the
Red Squirrel in Winter
Taylor Loen
Winter Ecology
Spring 2009
University of Colorado Boulder Mountain Research Station
Introduction
• Front Range Lodgepole pine (Pinus contora)
forest is a major habit for the Red Squirrel
(Tamiasciurus hudsonicus fremonti) because of the
predicted availability of the cone supply. (Finley.
1969)
• The bark beetle (Dendroctonus ponderosae)
infestation reduces the number of viable lodgepole
pine. Dead trees are known as beetle kill trees.
Parameters
• Q1: What is the relationship between pop.
of R. Sqs and the density of BK trees?
• Q2: What is the relationship between
frequency of interaction with BK tree and
BK tree density?
• Q3: How are the bk trees in H density areas
being used?
Results
Q1: What is the relationship between pop. of R. Sqs and the
density of BK trees?
• R. Sq population is lower in stands of high density
bk trees. (Koprowski 2005) (Matsuoka 2001)
• Thinned stands of lodgepole provide less food,
and less protection to predation than medium or
high density stands of healthy trees. (Sullivan &
Moses 1986)
• Average home range is about .56 ha = 5,600 m2=
1.38 acres. Average density was 1.3 sq/ha (Gurnell
1984)
Results
Q2: What is the relationship between frequency of
interaction with BK tree and BK tree density?
• Likelihood of
interaction increases
3.3% - 5.5% per
beetle
attacked/killed tree
in the squirrels home
range. (Pretzlaw. 2006)
Results
Q3: How are the bk trees in H density areas being used?
• Bk trees are used as foraging sites for bark
beetle larvae. (Pretzlaw 2006)
• Encounter rate determines the time it takes
for the squirrel to develop a prey model for
the beetle larvae. (Getty 1993; Tinbergen 1960)
Discussion
• Red Squirrel ranges are dependent on the food
available, therefore reducing the number of cone
producing trees will impact their survival in that
area. (Rusch & Reeder 1978)
• Their winter survival is highly dependent on their
midden stores to last them through a winter. (M.
Smith 1968, Streubel 1968)
Discussion Cont.
• Beetle killed lodgepole pines change the dispersal
of the squirrels in the area, but also increase the
likely hood of the squirrels interacting in some
way with bk trees. Which could change the
seasonal diet of the squirrel allowing it to save the
cones for the winter, since beetle larvae are not
cached. (Pretzlaw 2006)
• The inherent loss of trees will effect a novel
change in the habits of the front range red squirrel.
Summary
• High density bk trees/thinned stands of lodgepole
have lower populations of R. squirrels.
• The more bk trees there are the more likely the
interaction.
• Red Squirrels may feed on beetle larvae.
• Reduced number of lodgepole means more
competition for cones of other species.
• Winters will be tougher because of fewer available
lodgepole cones for storage.
References
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