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Squirrel nest site preferences

Casandra Brocksmith and Lauren Gray

Introduction

We looked at nest site preferences of squirrels in the Nature Park.  We chose this topic because we noticed a lot of squirrel nests in trees and we were interested in learning more about squirrel nesting habits.  

Squirrels typically live in forests throughout the United States and Canada.  They prefer hardwood nut-producing trees because these provide squirrels with the bulk of their diet (acorns, hickory nuts, beech nuts).  A squirrel's home range is typically one to eight acres and overlaps with other squirrels.  

Both male and female squirrels construct the nest.  They build the nest during the summer by weaving small branches together.  The nests are lined with grass, moss, pine needles, and leaves.  The nests are also known as "dreys" and are typically built 30 feet off the ground in the fork between a tree limb and the tree trunk.

Previous research by Cox et al. (2005) found that gray squirrels preferred to nest in oak and maple trees and that there was a correlation between nest height and tree height.  

Hypothesis

Squirrels prefer to build their nests in oak and maple trees of larger circumferences.  There will be higher numbers of nests in heavily wooded areas.

methods

We chose three sites.  Site 1 was along the W4 trail.  Site 2 was next to Big Walnut Creek.  Site 3 was located near the main entrance to the Nature Park.

At each site, we counted the number of squirrel nests, measured the height and circumference of each nest tree, and counted and measured trees 

results

We found six nests at site 1, 3 nests at site 2, and 3 nests at site 3.  There was no difference in the circumference of trees with nests and the circumference of trees without nests (p = 0.87).

The pie charts show the relative abundance of red oaks and other tree species at site 1.  The pie chart on the left shows the nest trees and 15 trees that were closest to the nest trees.  The pie chart on the right shows 50 trees near the area of site 1.  There was a significant difference in the composition of the trees (Fisher's exact test, p = 0.01).  About 50 percent of the trees near nest trees were red oak.  About 25 percent of the trees in the general vicinity were red oak.  These data suggest that squirrels build their nests in areas where there are more red oaks.

 

discussion

We found that squirrels choose to build their nests in areas with more red oak trees.  We could not test the hypothesis that squirrels nest more frequently in heavily wooded areas because our sample size was limited.  There was no difference in the circumference of nest trees and neighboring trees.  This shows that squirrels did not choose the largest trees.  Instead, the squirrels were looking for the best place in a tree to build their nests.

References

Cox, K., et al.  2005.  Nest-site preference of gray squirrels.  Journal of Ecological Research 7:  36-42.