(Left to right): UNIVERSAL PICTURES/Album/Alamy Stock Photo; Ondrej Prosicky/shutterstock

Is this monkey the inspiration for Dr. Seuss’s Lorax?

Theodor “Dr. Seuss” Geisel’s beloved picture-book ode to environmentalism is set in a fictional land of thneeds and truffula trees, but The Lorax may have a real-world counterpart. The orange, mustachioed titular character (pictured on the left, above) may have been based on the now-threatened patas monkey (Erythrocebus patas, shown at right), scientists report today.

Geisel wrote 90% of The Lorax while visiting the Mount Kenya Safari Club in Nanyuki, a region inhabited by patas monkeys. The researchers have no direct proof that the author encountered the animal during his stay, but his autobiography mentions that he likened the shape of Kenyan trees to his own style of illustration. He also included an illustration of what could be a whistling thorn acacia (Acacia drepanolobium) in The Lorax—a tree the patas monkeys depend on for more than three-quarters of their diet.

To make a stronger case, the researchers created mathematical models for the faces of several species of Kenyan monkeys. Next, they used an algorithm to group the faces based on the similarity of their features. The Lorax’s face most closely resembled that of the patas monkey, the team reports today in Nature Ecology & Evolution, as well as the blue monkey, another local species. The researchers say the Lorax’s voice, described in the book as a “sawdusty sneeze,” resembles patas monkeys’ wheezing alarm yell.

Ironically, given The Lorax’s strong conservation message, environmental changes have reduced the patas monkey’s range by half since 1991. Their primary food source—the acacias—are disappearing because of drought and land clearance for agriculture. In what the study’s authors call “a prophetic example of life imitating art imitating life,” the animal Geisel may have chosen to “speak for the trees” could one day exist only on the pages of his book.