Primates are often distinguished from other mammals by their greater emphasis on vision relative to other senses (Cartmill, 1992; Kirk, 2013). Many of the defining traits of early primates are adaptations of the visual system, such as a postorbital bar, greater orbital convergence and larger eyes (Heesy, 2008; Kay and Kirk, 2000; Kirk, 2013; Ross and Kirk, 2007). In comparative studies of extant mammals, primates are typically characterised by higher estimates of visual acuity (i.e. the ability to resolve fine details) and greater variation in colour vision and opsin genes (Jacobs, 2008, 2013; Kirk and Kay, 2004; Veilleux 2016; Veilleux and Kirk, 2009, 2014). Consequently, most hypotheses of primate evolutionary origins involve identifying ecological factors that selected for this increased visual performance in early primates. Given that most of these hypotheses propose a nocturnal niche (e.g. Cartmill, 1992; Rasmussen, 1990a; Sussman, 1991), identifying and understanding variation in visual function and ecology among nocturnal primates is particularly important.