Yellowstone National Park is a good place to see Rocky Mountain Elk. Elk were once found across much of North America, but their range is now greatly contracted.
The elk in this photo is a female. Females and young live in herds. Males either live alone or in groups of batchlors. During rutting season, females and young will move into harems with one or two males. Males coat themselves with urine-soaked mud, which attracts the females. I did not notice it at the time, but this female is urinating. This behavior is probably not marking territory, and no more complicated than it seems. (As we raced across Yellowstone in search of the Great Gray Owl, this photo is the only elk image I captured.)