As aspen leaves turn the gold of fall, grizzly bears in the greater Yellowstone area endure the final mania of their annual feeding frenzy before winter’s hibernation. The omnivorous bears compulsively pack on the pounds with berries, fish, carrion, whitebark pine seeds and a food unique to the Rocky Mountains—thousands of army cutworm moths.
Also known as miller moths, they are the adult form of an agricultural pest, the army cutworm, which migrates to mountain fields in early summer to feed on alpine flowers’ nectar. During the past 30 years, a handful of researchers have established the importance of moths as a food source for bears.