There are a handful of kangaroo rat species in the Sonoran Desert. The most commonly encountered one at Organ Pipe Cactus is Merriam’s kangaroo rat. You may notice some smaller kangaroo-rat-like rodents called pocket mice. It’s hard to tell exactly who you’re looking at if you only get a brief glance, but pocket mice are generally the smallest, at about the size of a Brussels sprout. Kangaroo rats are about palm-sized.