Australian researchers have shown that for the air-breathing, milk-producing, live-birthing creatures of the world, glowing under ultraviolet light is so common it's almost mundane.
Tests show a whole bunch of Aussie animals do it from wombats and Tasmanian devils to bandicoots and bilbies. So too do exotic species including zebras, leopards, armadillos and bears.
But what's less clear, after the world's broadest study to investigate the glowing propensity of mammals, is why.
Dr Kenny Travouillon is the curator of mammalogy at the Western Australian Museum and as such he cares for its vast collection of stuffed and preserved animals.
A couple of years ago, when news first broke that scientists in the US had accidentally discovered that platypuses glow under UV light, he grabbed a light and made a beeline for museum's taxidermy shelves.
Lo and behold, they lit up like the billboards in Times Square. Well, almost.
When Dr Travouillon shared his light bulb moment on Twitter, scientists were soon beating down his door saying it was time for a closer look.
In total, they found 125 species of mammal glow to varying degrees under UV light, via their fur and skin. The lighter the fur and skin, the more it tends to glow.
The results covered all 27 orders of mammals - suggesting it is a widespread ability.
Scientists also looked for patterns that might explain why it's a thing and why some animals glow from the stomach, for example, or the ears and feet, or all over, like wombats do.
"We took all that information about which part of the animal was glowing and looked for any correlation with things like diet, whether the animals were diurnal or nocturnal or tree dwellers, ground dwellers or aquatic," Dr Travouillon said.
While glowing was detected in animals that are active during the day and others that are active at night, slightly more nocturnal animals glowed.
That suggests it may play a role in visual signalling for nocturnal species, helping them to hook up or avoid each other.
But what about blind moles that live solitary lives, buried under the ground? Why would they bother with the whole glowing thing?
Dr Travouillon said the theory was that it might not be worth expending the calories needed to create skin pigment to lessen the glowing phenomenon.
"They don't care that they glow. They are buried underground, nobody can see them," he said.
As for the wombat's all-over radiance, he noted they don't have many predators and reckoned they might not care either.
Now that it's been established that many mammals glow - and that includes humans, something established some time ago - Dr Travouillon said it was time to move on to studies in living animals.
The peer-reviewed research by the Western Australian Museum, Curtin University and the Queensland University of Technology has been published in the journal Royal Society Open Science.
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