In the last few years, more and more mammals have been reported to fluoresce under ultraviolet light. Fluorescence is commonly reported amongst animals including birds, reptiles, and fish. But until now, no-one knew how common it was amongst mammals.

After testing more than 125 species of mammals, the research led by the Western Australian Museum’s Curator of Mammalogy Dr Kenny Travouillon, in partnership with Curtin University, determined that fluorescence amongst mammals is also extremely common.

“We were quite curious to find out about fluorescence in mammals. By using the spectrophotometer in the School of Molecular and Life Sciences at Curtin University, we were able to measure the light that was emitted from each specimen when exposed to UV light,” Dr Travouillon said.

“We recorded fluorescence in 125 species of mammals from the WA Museum’s Collection, covering all known orders of mammals, and the vast majority of mammal families – all of which fluoresced to varying degrees.”

Dr Travouillon said earlier reports of fluorescence in mammals happened to be mostly in nocturnal species, leading the researchers to think that fluorescence must be important for nocturnal mammals.

“Our study tested this theory to check if it was true or not. We ran an analysis to correlate the amount of fluorescence recorded in our study with ecological traits such as nocturnality, diet, and locomotion. In the end, we found that many diurnal mammals also glow, but nocturnal mammals glow a bit more.

“We also found that it was more common in ground-dwelling, tree-dwelling, and burrowing mammals, compared to their aquatic counterparts.”

Dr Travouillon said that fluorescence was in all-white to light-coloured hairs, which meant that dark pigmentation of hairs prevented fluorescence.

“There was a large amount of white fluorescence in the white fur of the koala, Tasmanian devil, short-beaked echidna, southern hairy-nosed wombat, quenda, greater bilby, and a cat – and while a zebra’s white hairs glowed its dark hairs did not.”

Orange leaf-nosed bat under UV light (c) WA Museum 

It is now clear that fluorescence is very common in mammals, likely the default status of hair unless it is heavily pigmented.

“While fluorescence is more common in certain types of mammals, such as our nocturnal marsupials, it doesn’t mean that it has a function, as there is very little UV light reflected from the moon at night.

“It may help brighten some parts of the animal so they can see members of their species from a distance. But before you start taking your UV light with you to look at nocturnal mammals, remember that UV light can damage their eyesight, and you should take a red light to do your spotlighting instead,” Dr Travouillon cautioned.

Dr Travouillon led the recently published paper All-a-glow: spectral characteristics confirm widespread fluorescence for mammals which can be viewed  https://royalsocietypublishing.org/doi/10.1098/rsos.230325