The Usage of the Digits of a Captive Aye-aye (Daubentonia madagascariensis)

Abstract

A study was carried out between July and August 1989 on the usage of the manual digits of one captive aye-aye (Daubentonia madagascariensis) at the Tsimbazaza Zoo, Antananarivo. Manipulation of the digits was examined by direct observation and by analysis of tapes taken with a video-camera. The third digit (the most slender) and the fourth digit (the longest) of both hands, were used fro scooping foods: the average duration of one scoop was 11.9 seconds for the third digit and 14.7 seconds for the fourth digit, with no substantial difference between them (t-test, p>0.05). The aye-aye alternated between using the third and fourth digits, according to the foods presented. The third digit was also used for tapping food. The average duration of one tapping bout was 2.9 seconds. The fourth digit was often used for grooming and for grasping a twig or holding onto wire mesh while traversing. This report forms the experimental part of a series of papers examining the hard-nut adaptation hypothesis of the aye-aye's ecological niche. In this investigation, the captive female aye-aye showed some extraordinary examples of feeding behavior. The aye-aye ate all foods except sugar cane, by using her third and fourth digits after tapping the food with her third digits. Primates often feed by holding a food item with the hands and biting off pieces directly with the mouth. But the aye-aye did not eat in such a manner. This feeding behavior shows the specialization for consuming the contents of hard nuts of ramy (Canarium spp.) under natural conditions, and that the aye-aye's morphological characteristics are closely adapted to such a feeding method.