The trick to finding good locations for camera traps involves finding spots that

The trick to finding good locations for camera traps involves finding spots that draw animals.

In this instance, a mountain lion came by a "scrape," or scent site, which can indicate which animals are in the area.

You can see a great example of what's called the flehmen response, in which the cat curls back its upper lip and inhales, allowing it to smell what else has been around this site lately.