Wildlife watching in Yellowstone National Park takes on a bit of a voyeuristic flavor in the fall, as the park’s famed mega-fauna embark in the pursuit of romance during their annual ruts in an often public spectacle that rivals any of the drama on The Bachelor. Visitors can hear the loud thunderclap of bighorn sheep clashing, the raucous bugling of bull elk, or the deep grunting and bellowing of bison—all performed in pursuit of a mate or mates.

In the fall, animals and birds prepare for winter. Bears eat constantly to fatten up before they slow down. Many birds are already on their migration path. Elk and other ungulates are preparing for the mating ritual, the rut. Take a look -- or stop and listen -- in many national parks this Fall and you'll catch a glimpse of this autumnal spectacular.

How do you make a fee-free day to a national park even better? By allowing visitors to not only volunteer, but also earn another fee-free coupon. If you think this sounds like a great idea, then come out to volunteer on September 25, National Public Lands Day!

Visit a national park in the Fall and you'll likely be enveloped by the brilliant colors of the season, crisp temperatures perfect for hikes, and wildlife on the move. In a week-long series we'll point to the best the park system can offer during this season.