Grand Canyon marks the Birthplace of Squirrel Speciation

As I was growing up, I was always fond of squirrels. I remember when my parents took me to the zoo and I asked them why the squirrels on the trees weren’t in cages. They told me they didn’t need to be because they weren’t part of the zoo. I admired their independence from being a zoo animal and the fact that they lived a carefree life without having to be a pet or a zoo animal. In my AP Biology class, we are learning about speciation. I happened to come across the speciation of the Kaibab and Abert squirrels. I found it rather intriguing and researched further into the topic.

Kaibab squirrel 3Kaibab Squirrel     🙂Unknown

Abert Squirrel    🙂

Arizona’s Grand Canyon was formed creating a geographic barrier between the squirrels that lived there. They could no longer contact and reproduce with each other. Two separate species inhabit the north and south rims of the canyon. The Kaibab squirrels inhabit the north rim and the Abert squirrels inhabit the south rim. According to National Geographic, this type of speciation is allopatric speciation. In the article, it says, “Allopatric speciation occurs when a species separates into 2 separate groups which are isolated from one another…When Arizona’s Grand Canyon formed, squirrels and other small mammals that had once been part of a single population could no longer contact and reproduce with each other across this new geographic barrier.”

This leads me to say that according to Macroevolution,  the type of reproductive barrier that is causing these 2 species to split is called Geographical Isolation. It says that, ” The Kaibab squirrel became geographically isolated from the common ancestor with its closest relative, the Abert squirrel in the North Rim of the Grand Canyon about 10,000 years ago.” This indicates that it is geographical isolation because the Grand Canyon is literally a physical barrier between the two species.

Furthermore, there was a study done on both the basic characteristic of both species. These characteristics include coat, coloration, size, shape, habitat, range, foraging, and feeding. For example, according to the study, one of their distinguishing characteristics is their range. In the article by Animals by Demand Media, it says that, “Abert’s squirrels have a relatively large range and can be found in parts of Arizona, Wyoming, Utah, New Mexico and Colorado in the United States, and from Chihuahua to southern Durango in Mexico.Kaibab squirrels have a much smaller range: They only exist in the ponderosa pine forests of the northern Kaibab Plateau.” A similar characteristic between the two species is their size and shape. According to the article, it says that, “Both Abert’s and Kaibab squirrels are a similar size and shape.These squirrels also have a similar skeletal structure, with no noticeable differences. They have short, broad skulls, with flattened frontal areas, and narrow, laterally compressed rostrums.”

Although these species were separated by a geographical barrier and could not unite their species once again because of geographical isolation, they have many similarities and differences that make them both unique wildlife species. The fact that speciation occurred at one of the most amazing land features in the world is mind blowing. I found this research really interesting and helpful. It made my love for squirrels grow even more!


“National Geographic Education Speciation.” National Geographic. N.p., n.d. Web. 05 Nov. 2015. <;. 
Corona, Lauren. “What Are the Characteristics of Abert & Kaibab Squirrels?” Animals by Demand Media. N.p., n.d. Web. 5 Nov. 2015. <;.
“Allopatric Speciation.” BIO 304. Ecology & Evolution: Macroevolution. N.p., n.d. Web. 05 Nov. 2015. <;.

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