Why testing lemur color vision is harder than it looks. Duke Research Blog, March 18, 2016. Elphaba the aye-aye is not an early riser. A nocturnal primate with oversized ears, bulging eyes and long, bony fingers, she looks like the bushy-tailed love child of a bat and an opossum. Elphaba is one of 14 aye-ayes at the Duke Lemur Center in Durham, North Carolina, where researchers have been trying to figure out if these rare lemurs can tell certain colors apart, particularly at night when aye-ayes are most active. But as their experiments show, testing an aye-aye’s eyesight is easier said than done.