A Primate of a Different Color
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Mammals have evolved to live all sorts of lifestyles. Some dive deep in the ocean. Some burrow under the ground. Some swing through the trees. Some even fly. But one thing they almost all have in common is the color of their irises. Bat, mouse, pronghorn, or whale, all have brown eyes.
There are some exceptions among domestic animals. Cats’ eyes, for instance, can take on a greenish or yellowish hue. Some even have blue eyes, although this trait is often linked to white fur and deafness and so is sometimes termed a mutation instead of a variation.
Among humans it’s a little bit different. In some parts of northern Europe over 50% of the population have blue eyes. In the United States it’s more like 17%. But worldwide the number drops to only 2%, a minuscule proportion of the entire population. But, surprisingly, there is one type of primate where the proportion is 100%.
Blue-eyed black lemurs are almost as rare as their startling eyes would lead you to believe. Although first described by the British Zoologist Sclater in the 19th century, they were not “discovered” in the wild until the 1980s. Today, they are found only in one very small patch of forest in northwestern Madagascar, and are critically endangered.
The fact that they are so rare in the wild and live in such an inaccessible area means that little is known about their behavior. Like their cousins, the black lemurs, their coloration is “sexually dimorphic”, which means that it’s easy to tell the males from the females. Male blue-eyed lemurs are completely black while females are almost blond. Babies are born a brownish color and only acquire their parents’ coloration as they mature.
Like other primates, these lemurs are very social. They generally live in groups of fewer than 10 individuals, with the ratio of male to female usually skewing towards the males. Even so, it’s the females who are dominant and constrain access to food and mating.
Although probably never numerous, today there are less than 1,000 blue-eyed black lemurs living in the wild. Even so, this small number has big consequences for their forest home. Their favorite foods are fruits, nectars, and pollens. As they forage throughout the day they spread excess pollen grains to widely separated plants and distribute seeds far from the parent trees as they pass through the lemurs’ digestive tracts. In this way they contribute to the richness of their ecosystem and create a more robust forest.
Conversely, when the forest is destroyed by “slash and burn” farming, the lemurs are forced to eat human crops instead. Unfortunately this brings them into direct conflict with humans and leads many of them to be killed as “agricultural pests”.
Male & Female Blue-eyed Black Lemurs Showing Sexual Dimorphism
Thankfully, lemurs are finally getting some help. There are now breeding populations at several facilities around the world and more attention is being paid to preserving what’s left of Madagascar’s wild lands. Hopefully, as new protections are instituted and more are bred at institutes such as the Duke Lemur Center, there’s still a chance to pull these unusual prosimians back from the brink of extinction.