Implications of Beetle Killed Lodgepole Pine Effects on the

Red Squirrel in WinterTaylor LoenWinter Ecology

Spring 2009University 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.

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