Cougars and Trees in a Trophic Cascade

This activity guides the analysis of a published scientific figure from a study that investigated the effects of tourism on cougars and cottonwood trees in a national park.

In 1918, Utah’s Zion National Park was established to protect forests and rivers from human activity. But as more tourists began visiting the park, they displaced cougars (mountain lions), the top predator of herbivores called mule deer, from certain areas. In this study, scientists compared vegetation in areas of the park with and without cougars. The figure shows the age structure of cottonwood trees found in the park in 2015. Panel A shows trees from an area where cougars were common, and Panel B shows trees from an area where cougars were rare. The “Educator Materials” document includes a captioned figure, background information, graph interpretation, and discussion questions. The “Student Handout” includes a captioned figure and background information. The original article is also provided as a download.

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