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

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The following essay is excerpted from Natural Histories: Extraordinary Rare Book Selections from the American Museum of Natural History Library (Sterling Signature, 2012), edited by Tom Baione, the Museum Library’s director. The essay was written by Eleanor Sterling, director of the Museum's Center for Biodiversity and Conservation. 

Victorian England was an exciting time for biologists with sufficient information to synthesize an ever-growing set of observations on the morphology, behavior, and distribution of plants and animals, with the goal of refining categories and delimiting species and their relationships to one another.

An increasing number of explorers were also on the hunt for odd organisms that defied categorization, or at least tested the boundaries. Arguments between passionate scientists aired not just in meetings and written proceedings, but also in the popular press. Sir Richard Owen was at the epicenter of many of the crucial debates of the time.

Sir Richard Owen

Sir Richard Owen (1804-1892), painted in about 1845

© National Portrait Gallery, London


An accomplished naturalist with a six-decade career, more than 600 scientific papers, and a stint as a biology tutor to Queen Victoria’s children, Owen is probably best known today for having coined the term “dinosaur,” but his work on primates was unsurpassed at its time.

Owen was particularly taken with an unusual primate, the aye-aye (Daubentonia madagascariensis), which is found only on the island nation of Madagascar. For the first 100 years after the first aye-aye was brought to Europe in the 1780s, debate swirled over whether it was a rodent, a primate, or most closely related to a kangaroo.

Aye-aye photograph

Found only on Madagascar, aye-ayes, which are nocturnal, are now known to be primates. Like other primates, they have forward-facing eyes and opposable thumbs.

Frank Vassen (Flickr)


The root of this confusion lay in the aye-aye’s odd collection of behavioral and morphological 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.

It uses its middle finger to tap along a branch and moves its ears forward and back to help locate hollow channels within the wood created by wood-boring insect larvae. Once it detects a channel, the aye-aye uses its specialized front teeth to pry open the wood and then inserts one of its fingers to extract the larvae.

Owen put arguments about the aye-aye’s taxonomy to rest in 1863 with his elegant and, at times, lyrical Monograph on the Aye-Aye (Chiromys madagascariensis, Cuvier), which opens with a description of the history of scientific study of the aye-aye and moves to a painstakingly detailed description of its anatomy.

Click on the image for a closer look.

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


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.”

From Monograph on the Aye-Aye, by Sir Richard Owen, published in 1863. A copy is in the collection of the Museum's Library.

© AMNH/D. Finnin


Stunningly beautiful hand-colored lithographic illustrations of the pelage (coat), skeleton, and unusual morphological features accompany the text. The illustrator, Joseph Wolf, was one of the most accomplished of animal painters. He not only studied the alcohol specimen that Owen had received in 1859 but also watched the activities of a young female aye-aye in the London Zoo. The aye-aye is a nocturnal creature, which meant that Wolf had to observe the animal at night by candlelight.

 A version of this story appears in the summer 2013 issue of Rotunda, the Member magazine.

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