Twin three-month-old red pandas (Ailurus fulgens fulgens) huddle together at the Lincoln Children's Zoo. Sartore photographed the pair as part of his Photo Ark project, through which he is documenting thousands of rare species.
"Half of all the species on Earth could be headed irreversibly toward extinction by 2100. Not if I can help it," Sartore says. "That's the idea behind the Photo Ark: getting the public to look these creatures in the eye, then care enough to save them while there's still time."
Learn more about the Photo Ark and see more pictures from the project.