ST. GEORGE — Thousands of years ago, a desert-hardy plant, now quintessentially southern Utahn, moved from what is now northern New Mexico across the Mojave Desert. And a native species of rodent genetically adapted to eat its toxic leaves.
The creosote bush is a species that can be found across the Mojave Desert and is native to southern Utah. The desert-hardy shrub is evergreen and produces small yellow flowers, according to the Arizona-Sonora Desert Museum. Creosote has several adaptations that help it survive in the desert, including deep roots to access water from the water table, small leaves that lose less water than large leaves and a waxy coating on its leaves that reduces water loss.
The plant invests "a huge amount of energy" into creating the resin coating, which comprises approximately 25% of the leaf's weight and contains various toxins, M. Denise Dearing told St. George News. Dearing is a distinguished professor of biology at the University of Utah and principal investigator at the university's Dearing Lab.
Additionally, the toxins deter herbivores, like range animals, from eating the bush's leaves. Despite this, some animals still feed on creosote, such as pollinators, creosote bush grasshoppers, chuckwallas and other reptiles, kangaroo rats and wood rats. Wood rats, also known as pack rats, are one of the only species known to tolerate a diet high in creosote bush.
But the creosote bush wasn't always common in southern Utah, and it wasn't always a staple food for wood rats.
