Iridescent mammals are much more common than we thought

More than a dozen species of mammals sparkle and shine purple and green, like precious opals. Their fur is iridescent, which means that its color seems to change depending on the orientation of the animal compared to the spectator. The effect is similar to the colored sparkle of an oil slick, or to the metal dazzling of hummingbird feathers – and it is more common in mammals than biologists thought.

Jessica Leigh Dobson at the University of Ghent in Belgium studied color in mammals using specimens at the Royal Museum for Central Africa, also in Belgium, when she noticed an electric blue glow on the fur of a tropical vlei rat (OTOMYS TROPICALIS).

“I immediately returned to the office to see if he was documented anywhere, because everything I had read for telling me [mammal] Irition is only found in golden taupes, ”explains Dobson. Golden moles are African mammals more closely linked to Aardvarks and elephants than real beauty grains, their name derived from their hairs in the shape of garlands.

Dobson searched in scientific literature and found occasional mentions of the brilliant fur of other species of mammals dating from the 1890s. Investigating further, she and her colleagues examined fur on mammal specimens which were associated with irritation anecdotal relationships – or which were closely linked to species with such reports. They used an optical microscope to light the fur to different angles and analyzed the wavelengths – and therefore the colors – of the light reflected by the hairs.

The analysis revealed that golden taupes are not only shimmering. The 14 additional mammal species have iridescent layers, including 10 rodents and the giant otter round (Potamogal Velox), a semi-ciel predator that is neither Otter nor Shrew. Six of these species had never been considered before iridescent in the scientific literature.

“It is really pleasant to see such a detailed description of a previously sub -direct -and often not described phenomenon -,” said Beth Reinke at Northeastern Illinois University in the United States, which was not involved in the study.

When the researchers looked at the hair of these iridescent mammals under a high power microscope, they found that they were all unusually smooth, each made of a series of sub-parallel layers which were more compressed than the layers inside the typical mammal hair.

“Each layer folds the light in a slightly different way and creates the changing colors,” explains Dobson.

Researchers think that shine is probably a by-product of other hair adaptations. Most of these mammals are hollow or swimming species, and smooth hair surfaces can help keep the fur clean in dirty or humid environments.

It is however possible that iridescence serves a function, perhaps for visual communication, as is the case in many birds, explains Dobson. New discoveries open the door to explore this possibility.

There could be many new opportunities to do exactly that. In 2024, a species of newly discovered handle of Indonesia was described as having somewhat brilliant fur. Dobson suspects that there may be even more iridescent mammals, always unrecognized.

“Especially when we consider that there are about 2,500 species of rodents, and we have examined a small fraction.”