The ability to perceive colors may not be as exclusive to daytime animals as previously thought. New research on the sugar glider (Petaurus breviceps), published on March 4, 2025, reveals this nocturnal marsupial not only possesses trichromacy—a system of color vision allowing the perception of three different colors—but also exhibits sensitivity to ultraviolet light.
This groundbreaking study, conducted through various behavioral tests, genetic analyses, and retinal examinations, sheds new light on the capabilities of color vision among nocturnal species. Prior to this research, scientists largely believed color vision was primarily beneficial for diurnal animals living under the bright illumination of the sun, with nocturnal species relegated to dim hues of gray due to low light conditions.
Researchers found significant behavioral evidence showing sugar gliders’ ability to perceive ultraviolet light. During the single color discrimination tests, sugar gliders consistently chose UV light over dark conditions, indicating strong UV sensitivity. For example, one glider selected the UV light 37 out of 45 trials. The presence of yellow sensitivity was also identified, with two gliders displaying significant preferences during tests.
Utilizing statistical models, the study demonstrated the group of gliders had overall UV sensitivity, irrespective of sex, and were capable of distinguishing colors such as yellow, blue, and green. Such abilities could significantly aid these animals when foraging for food, enhancing their visual contrasts among fruits, flowers, and insects during the night.
The genetic investigations revealed the presence of three key opsins responsible for color vision: rhodopsin, short-wavelength sensitive 1 (SWS1), and long/medium-wavelength sensitive opsin (LWS). Phenylalanine was detected at position 86 of the SWS1 gene protein sequence, supporting the hypothesis of UV sensitivity among the gliders. While the study found expected results, researchers noted unclear evidence of medium-wavelength sensitivity, as associated genes were not conclusively identified within the sugar glider genome.
This study aligns the sugar glider with other Australian marsupial species exhibiting trichromacy, such as the quokka and the fat-tailed dunnart, marking the sugar glider as the fifth known trichromatic marsupial. The authors discuss how this phenomenon reflects the evolutionary advantages of color vision, providing nocturnal species with enhanced capabilities to navigate complex environments and identify food sources.
Interestingly, it raises questions about how many other nocturnal species, previously categorized primarily as dichromats, might actually possess hidden or underutilized capacities for color vision. The study serves as evidence for the adaptive significance of trichromacy and highlights evolutionary strategies employed by mammals living under selective pressures of low-light habitats.
Main trends observed among nocturnal mammals indicate the retention of color vision genes amid evolutionary pressures. This research implies color vision could be consistently beneficial across differing environments and taxa, shaping the ecological niches these species occupy.
Currently, many questions remain about the genetic bases of color sensitivity and adaptations among various marsupials. Future research will need to bridge the gaps remaining concerning the genetic and evolutionary rationale behind nocturnal vision capabilities to promote conservation efforts for these unique species.