A team of researchers has found that some female lemurs have trichromatic color vision while all other lemurs of that species are colorblind. In the study, the researchers discovered that females with improved color vision not only had an edge on competition but also provided advantages to their home group. The details are in a paper that was just published in the journal Scientific Reports.
The Verreaux’s sifaka (Propithecus verreauxi) is a medium-sized lemur species that lives in the forests of Madagascar. Sifakas live a mostly arboreal life, rarely coming down to the ground. In fact, when not in trees, their only form of locomotion is a rather awkward-looking hop. They are herbivorous and consume a variety of plants and fruits. Sifaka lemurs live in matriarchal groups led by dominant females. Sifakas are highly social, cooperative animals known for reconciliation behaviors after a conflict, including grooming and cuddling. It’s important to study lemurs to fully understand primate evolution but most lemur species are critically endangered.
Researchers from The University of Texas studied multiple sifaka groups in Kirindy Mitea National Park over a ten year period. Some of the groups contained at least one female with trichromatic color vision. In trichromatic color vision, the eyes contain three types of cone cells. The majority of humans have this type of vision. Most lemurs (including all males), however, have dichromatic vision and are essentially colorblind. The team monitored the populations over a ten year period to see if trichromatic color vision was useful to a lemur group.
The team found that trichromat females had healthier weights and more reproductive success. The same females were also more likely to have their infants survive the first year. Interestingly, dichromat group members benefited from the presence of a trichromat female. Groups containing at least one trichromat female had higher BMI scores on average. During the dry season, when food is difficult to find, trichromat females had an easier time finding quality food sources. This was a benefit shared with her infant and the rest of the group.
The team’s findings show that trichromat females are more successful and offer benefits to the rest of their group. This could lead to the mutation becoming more common as time goes on. The findings will also help scientists study the evolution of trichromatic color vision in primates, including humans.
Veilleux et al. Group benefit associated with polymorphic trichromacy in a Malagasy primate (Propithecus verreauxi). Scientific Reports (2016).