Meet the newest member of the fluorescent mammal club
By Cara Giaimo
Platypuses do it. Opossums do it. Even three species of North American flying squirrel do it.
And, breaking news: Two species of rabbit-size rodents called springhares do it. That is, they glow under black light, that perplexing quirk of certain mammals that is baffling biologists and delighting animal lovers all over the world.
Springhares, which hop around the savannas of southern and eastern Africa, weren’t on anyone’s fluorescence bingo card.
Like the other glowing mammals, they are nocturnal. But unlike the other creatures, they are Old World placental mammals, an evolutionary group not previously represented. 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.
But mammals, it seems, don’t tend to have these pigments. A group of researchers, many associated with Northland College in Ashland, Wisconsin, has been chasing down exceptions for the past few years — ever since one member, biologist Jonathan Martin, happened to wave a UV flashlight at a flying squirrel in his backyard. It glowed eraser pink.
The researchers then went to the Field Museum in Chicago. When the team 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 and an author of the new paper, published in Scientific Reports.
Over the next several years, the researchers examined 14 springhare specimens from four countries, some male and some female. All showed fluorescence — many in a patchy pattern, which was unique among mammals they’ve studied, Olson said.
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 who worked on the paper.
But the biggest question is: why?
The springhare findings in particular provide some avenues for exploration. 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, Olson said.