Visual recognition in a nocturnal primate

Nocturnal primates primarily rely on olfactory and acoustic cues for conspecific recognition and communication, but researchers have comparatively understudied the role of vision. Here, we investigated how visual cues function in the nocturnal aye-aye (Daubentonia madagascariensis) to address this gap. We used a Tobii Spectrum Pro eye tracker to measure attentiveness to visual stimuli in six captive aye-ayes (f: 5, m: 1) across two gaze-tracking paradigms. We employed generalized linear mixed models, including subject identity as a random effect, to assess the relationship between stimulus type and gaze metrics. In the Thatcher Illusion paradigm, subjects made more whole fixations when viewing non-Thatcherized images than Thatcherized ones. In the preferential-looking paradigm, subjects also demonstrated greater attentiveness to conspecifics compared to other species. However, subjects did not show significant differences in their attention among individual conspecifics. Our results demonstrate that aye-ayes use visual cues for conspecific recognition. These findings provide new insights into primate evolution, adaptations to the nocturnal niche, and the trade-offs between olfaction and vision.