The aye-aye (Daubentonia madagascariensis) possesses a hand with highly specialized the third and the fourth fingers. We observed the use of those fingers in various activities in four free-ranging aye-ayes. We found that the thin third finger was used exclusively or preferably for tapping, inserting into the mouth (probably for cleaning the teeth), probing for nectar, kernels and insects in bamboo, twigs, and live wood. In contrast, the robust fourth finger was used preferably when eating jackfruit (Artocarpus heterophyllus). When probing for invertebrates in soft plant tissues and in dead wood, both fingers were used. To extract the contents from coconuts, the two fingers were apparently used for different tasks. From this unique study, we conclude that the third finger appears to be specialized for use in tasks requiring high mobility, sensitivity and precision, whereas the fourth finger appears to be specialized for tasks requiring strength, scooping action and deep access.