These holes were made by Sandstone Bees (Anthophora pueblo). Instead of building nests of wax, or carving burrows in the ground or wood, the Sandstone Bee digs holes in rock. Named after the Pueblo Native Americans, who lived in cliff shelters, Sandstone bees slowly dig burrows into fairly hard sandstone, and have even been known to dig into cement.

Their homes in the rock help protect them from predators, flash floods, parasites, and other dangers. The tunnels are safe enough that a young bee can "skip" a year or two, waiting in its protected home during periods of drought. They are currently being studied to learn more about their behavior and role as pollinators.