As in any desert environment, the best time to see wildlife in Arches is early morning or evening. Summer temperatures keep most animals tucked away in cool places, though lizards crawl around all day, so if you happen to be in the right place at the right time you'll spot one of the beautiful, turquoise-necklace-collared lizards. It's more likely you'll see the Western whiptail. Mule deer, jackrabbits, and small rodents such as pack rats are usually active in cool morning hours or near dusk. You may spot a lone coyote foraging day or night. The park protects a small herd of desert bighorns, and some of their tribe are often seen early in the morning grazing beside U.S. 191 south of the Arches entrance. If you are fortunate enough to encounter bighorn sheep, do not approach them. They have been known to charge human beings who attempt to get too close. The park's mule deer and small mammals such as chipmunks are very used to seeing people and may allow you to get close—but don't feed them.
At sunset, the rock formations in Arches glow like fire and you'll often find photographers behind their tripods waiting for the sweet light to descend upon Delicate Arch or other popular park sites. The Fiery Furnace earns its name as its narrow fins glow red just before the sun dips below the horizon. Full-moon nights are particularly dramatic in Arches as the creamy white Navajo sandstone reflects light and eerie silhouettes are created by towering fins and formations.