Summary

The Columbian ground squirrel (Spermophilus columbianus) is a diurnal herbivore that lives in the Northwest United States and Southeast Canada. The ground squirrel lives in elevated alpine or sub-alpine regions, preferring meadow steppe. Columbian ground squirrels are only active for 3-4 months out of the year and the rest of the time is spent hibernating. They typical emerge from hibernation in mid April and enter hibernation in early August.

The long hibernation can be attributed to two major factors: limited resources and heavy predation. The high elevation that the squirrels live at limits the amount of food that is available. Typically by the end of July an abundance of the high quality forage that the squirrels subsist on is gone. Due to this fact, the squirrels will enter hibernation until the following April. Also contributing to the long hibernation is the heavy predation the squirrels face.

Columbian ground squirrels face a wide variety of land and air predators. Thus, if there is no real resource benefit to encourage them to remain above ground and active, then their next best option is to enter hibernation.

If the Columbian ground squirrel was found at a lower elevation with more abundant resources, it is distinctly possible that they would enter hibernation later despite the predation threats. The abundant resources would be beneficial to late emerging juveniles and underweight yearlings. These individuals would have more resources to help them achieve a necessary weight to survive the hibernation, since they are not fully grown and at a disadvantage when compared to adults.

Columbian ground squirrels live in colonies that are divided into small clusters. The clusters consist of philopatric females, non-reproductive members of both sexes, and one or two territorial males. These territories are maintained by the territorial males through various dyadic encounters, however they are not static.

The mating system of the Columbian ground squirrel can be described as hierarchical promiscuity. Dominant territorial males get access to the females first, but are not the only ones to mate with them as non-dominant males copulate with females quite frequently. Successful females break off from the group and become defensive towards most other individuals. The female will give birth to 3-5 offspring on average. These juveniles will emerge and then have to fend for themselves upon emergence from the natal burrow. Males tend to disperse into new territories while females remain in the territory where their natal burrow is located.

In short, the Columbian ground squirrel has adapted well to its surroundings. Its long period of hibernation protects it from the vast array of predators that it faces. Furthermore, the hibernation allows them to use minimal amounts of energy to stay alive long enough until next season. If they were to remain active during the months of August – April, they would surely die because of starvation and predation. Because of these adaptations, the Columbian ground squirrel has not only been successful, but has thrived where it is found.  

This website was completed in partial fulfillment of the requirements for Biology 323, Animal Behavior, at Davidson College in the Spring Semester 2008.

Please send any comments, questions or suggestions regarding this website to Kevin Cook or Professor Verna Case.