What is this mysterious rat-kangaroo-primate? Meet the Aye-Aye!

For more than a century after Europeans first encountered the mysterious aye-aye of Madagascar in the 1780s, scientists and biologists just could not figure out if the weird beast was a rodent or a kangaroo or some bizarre type of primate. Guess what it really is ....


An Obsession with Oddity: Sir Richard Owen and the Aye-Aye

For the first 100 years after the aye-aye was brought to Europe in the 1780s, debate swirled. Was it a rodent, a primate, or most closely related to a kangaroo? Found only in Madagascar, the unusual aye-aye has an odd collection of traits that make it appear to be composed of spare parts of other animals: continuously growing front teeth, batlike ears, a foxlike tail, abdominal mammary glands, claws on most digits, and spindly, dexterous middle fingers.

Image: A hand-painted lithograph from Monograph on the Aye-Aye, published in 1863 and written by Sir Richard Owen. The illustration is by Joseph Wolf. © AMNH/D. Finnin


Sir Richard Owen, an accomplished naturalist with a six-decade career, put arguments about the aye-aye's taxonomy to rest in 1863. Probably best known today for having coined the term "dinosaur," his work on primates was unsurpassed at the time. In his elegant and, at times, lyrical Monograph on the Aye-Aye (Chiromys madagascariensis, Cuvier), Owen opens with a description of the history of scientific study of the aye-aye and moves to a painstakingly detailed description of its anatomy.

Frank Vassen (Flickr)

This description focuses attention away from the striking unusual characteristics, like the continuously growing teeth, and toward primate-like characteristics such as forward-facing eyes and an opposable thumb, providing firm evidence for why the aye-aye should be classified as a primate.


Owen paired his observations on the aye-aye’s unusual anatomy with accounts of its behavior to narrate a story of a tight relationship between physical and behavioral traits—“of eyes to catch the least glimmer of light, of ears to detect the feeblest grating of sound, the whole determining a compound mechanism to the perfect performance of a particular kind of work.”

This post is adapted from an essay by Eleanor Sterling, director of the Museum's Center for Biodiversity and Conservation, that originally appeared in Natural Histories: Extraordinary Rare Book Selections from the American Museum of Natural History Library. Read the full essay here.