Iridescence is a trait that is seen in many animals, most commonly fish, insects, and even birds. Up until recently, it was thought that the Golden Mole was the only mammal that sported this shiny feature.

There were anecdotal stories about other mammals having iridescents, but those had not yet been confirmed. So, with that in mind, a team of researchers set out to test the fur of more animals to see whether this trait was indeed rare or not.

For the study, they took 14 species from the Royal Museum for Central Africa and analyzed their fur. The species included five animals with anecdotal evidence of iridescence, five that were thought not to have it, and three more from the golden mole family for comparison.

Once the samples were collected, the team analyzed the fur using multiple different instruments, including microspectrophotometry, scanning electron microscopy, and transmission electron microscopy. According to the study, which was published in the Journal of the Royal Society Interface:

“All iridescent hairs examined show tightly compressed cuticular scales, varying in number but all appearing to create a somewhat smooth surface.”

Surprisingly, there was iridescence found in all 14 of the samples that were studied. The mechanisms of iridescence were all similar as well, with the hairs having multilayer thin-films in place.

The study shows that this trait is far more common than previously believed, but it does not fully explain why the trait exists. Many of these animals, including the golden mole, are blind or mostly blind, spending much of their life underground.

Having iridescent fur would not be a trait involved with mate selection in animals, which makes it more unusual as an evolutionary option. The researchers suggest that the trait’s benefits may actually be focused on having a smoother surface, which could help the animals to burrow through the ground more easily.

The surface of the hairs may also help to keep them clean and avoid dampness while underground, which could be advantageous. Further study will undoubtedly be needed not only to determine why they have this trait, but also to determine how widespread it is among mammals.

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