When mammals get fluorescent

9 mammals fluorescent When mammals get fluorescent Arboreal

Two species of rabbit-size rodents called springhares, which hop around the savannas of southern and eastern Africa, glow under black light (ultraviolet light). A perplexing quirk of certain mammals that is baffling biologists and delighting animal lovers all over the world.

Their glow, a unique pinkish-orange the authors call “funky and vivid,” forms surprisingly variable patterns, generally concentrated on the head, legs, rear and tail.

Fluorescence is a material property rather than a biological one. Certain pigments can absorb ultraviolet light and re-emit it as a vibrant, visible color. These pigments have been found in amphibians and some birds, and are added to things like white T-shirts and party supplies.

But mammals, it seems, don’t tend to have these pigments. A group of researchers, many associated with Northland College in Ashland, Wis., has been chasing down exceptions for the past few years. When the team, armed with curiosity and blacklights, tried a drawer that housed preserved springhares, they beamed back.

“We were equal parts shocked and excited,” said Erik Olson, an associate professor of natural resources at the college. “We had so many questions.”

Chemical analysis of springhare hair found that the fluorescence comes largely from a set of pigments called porphyrins, which have also been found to cause this effect in marine invertebrates and birds, said Michaela Carlson and Sharon Anthony, chemists at Northland College. 

But the biggest question is: why? There is a possibility that fluorescence helps animals hide from predators with UV-sensitive vision, by absorbing wavelengths that would otherwise be brightly reflected and emitting less visible ones. In that case a patchy pattern like the springhares’ might be another asset, Dr. Olson said.

“Are these species all found on one part of the mammalian phylogenetic tree? Certainly not,” said Tim Caro, a professor of evolutionary ecology at the University of Bristol in England who was not involved with the research. “Do they all have one sort of lifestyle? No” — all eat different things, he said. “Are they using this delightful coloration to attract mates so we might see a characteristic signature of one sex but not the other fluorescing? No, that does not happen either.”

That “there is no pattern,” Dr. Caro said, suggests that “either we don’t know the function of this sort of coloration, or there is no function at all.”

According to Dr. Olson, there’s only one thing to do: Keep shining those blacklights.

Photo: J. Martin and E. Olson, Northland College

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