Dr. Kenny Travouillon turned off the lights and went straight to the shelf containing the stuffed platypus, armed with an ultraviolet flashlight to try something. Would the monotreme glow?
“All the platypus were glowing,” says Travouillon, curator of mammals at the Museum of Western Australia in Perth. “We passed with other mammals and found that they were glowing too.”
The museum’s collection of stuffed mammals has around 65,000 specimens of roughly 800 different species, including all of Australia’s many wonderful and occasionally bizarre animals.
Under ultraviolet light, creatures including bilbies, bandicoots, wombats, flying foxes, microbats, Tasmanian devils and echidnas took on a distinctive disco-like glow. The kangaroos, however, were “quite disappointing.”
Travouillon’s urge to point an ultraviolet torch at his specimens was triggered by a scientific article in October in Mammalia magazine and then reported in the New York Times.
The researchers had thrown ultraviolet light on two dissected platypuses collected in Tasmania, one dating from 1889, and which is kept at the Field Museum of Natural History in Chicago. The animals gave them back their shine.
Now scientists are wondering why. Was the glossy fur an evolutionary leftover or was it somehow useful to marsupials and other Australian animals?
Monotremes They are a curious order of egg-laying mammals that live only in New Guinea and Australia: the platypus and four species of echidna.
Their fur glowed green and cyan under different ultraviolet lights that glow at different wavelengths. This, the researchers said, was “the first report of biofluorescence in a monotreme mammal under ultraviolet light.”
But a few months earlier, zoologist Linda Reinhold was in the rainforests of North Queensland looking for shiny mushrooms. In the Queensland Mycological Society newsletter, Reinhold said that he had found 14 species that fluoresced under his UV flashlight. But she was also looking for something more.
“Realizing that marsupials were too skittish for fluorescence photography, I spent three days looking for roadkill,” wrote Reinhold.
On a path next to a field, he found two dead northern brown bandicoots. To the human eye, they were a dull, lifeless brown. But under his ultraviolet flashlight, the corpses were a parade of pinks and yellows.
Elsewhere, a defeated platypus turned purple and green under the torch.
‘It was like seeing the Macca poster’
If biofluorescence were simply an artifact of the chemicals used to preserve stuffed animals, then Reinhold’s run-over animal’s fur would not have ignited, nor would the fur of live animals. Tasmanian Devils at Toledo Zoo – another institution that became curious with an ultraviolet torch.
One answer could lie in research carried out nearly 20 years ago and started by Professor Lyn Beazley, a celebrated neuroscientist who was the first woman to take over as chief scientist when she won the post in Western Australia in 2006.
In the early 2000s, Beazley was researching the vision of honey opossums and thick-tailed dunnarts. In A study, found that these two species had cells in their eyes that would give them the ability to see ultraviolet light.
But in an additional study, Beazley and his colleagues put dunnarts in a maze and tempted them with crickets and mealworms using ultraviolet light to see if the animals could actually use the ability. They could.
“It was a lot of fun,” says Beazley of Murdoch University. “They knew there was no reward with the other colors. For them it was like seeing a Macca [McDonald’s] sign – there was going to be a reward. “
Beazley and his colleagues had established that these little mouse-like marsupials could see in ultraviolet rays and use that ability in the real world, something that the mammals reading this story cannot do.
“What is quite clear is that most animals can see UV rays. But we can’t, ”says Beazley.
“Fish, amphibians, birds… but it was the mammals that lost and that is why it fascinated us so much that the marsupials could see it.
“As human beings, we are interested because we cannot see it, but for animals it is just there.”
Beazley believes it could have multiple uses in the animal kingdom.
Rodent urine, like human urine, glows under ultraviolet light but birds of prey don’t need a UV flashlight to see the urine trail which can lead to a juicy meal. They can just see it.
Beazley says that some animals that have areas on their bodies, such as fur or skin, that emit light in the wavelengths of ultraviolet rays, can use it to signal potential companions or rivals.
With the animal kingdom awash in ultraviolet rays that humans cannot see, the patterns and colors of ultraviolet rays could have a wide range of uses that are difficult for humans to understand, he says.
For animals like the platypus, which are active at dusk and dawn, he says the ability to distinguish colors could be vital in foraging for food or avoiding prey.
Possums’ vision is particularly attuned to the wavelengths around the color orange, Beazley says, and that could help them reach their favorite banksia flowers just when the nectar is ready.
“I would want to get to the right flowers and I would want to get there first,” she says.
All this UV curiosity has fueled more formal scientific endeavors seeking answers to key questions.
Reinhold, from Cairns, tells Guardian Australia that he’s starting a university research project in 2021 loosely titled: “Fluorescence in Mammals: Prevalence and Causes.”
At the Western Australian Museum in Perth, Travouillon has been sharing images of glowing Australian animals on Twitter, but expects a more formal scientific publication next year.
He will work with Professor Simon Lewis at Curtin University in Perth, who leads research on forensic techniques at crime scenes, including the use of different light sources.
Lewis says: “We have access to instrumentation that will allow us to investigate the spectral characteristics of the apparent fluorescence. This will allow us to determine if it is really fluorescence and not some other optical phenomenon ”.
Travouillon has a warning for members of the general public who wish to undertake their own research on the secret light of animals: do not light an ultraviolet torch near their eyes, it could damage their eyesight.
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