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Nightclub goers will be familiar with the trippy experience of seeing clothes ‘glow’ under ultraviolet (UV) light – an effect known as fluorescence.
An Australian study now shows that this phenomenon is widespread in mammals, including the domestic cat species (Felis catus).
In addition to cats, fluorescence was found in 125 species, including bats, koalas, zebras, moles, polar bears and dolphins, they report.
In the same way that it helps us see other people flit across the dance floor, it can help animals notice each other in low light, such as the dead of night.
Previous studies have shown that fluorescence is observed in birds, reptiles, corals, mollusks, scorpions and other arthropods, amphibians such as frogs and even fish.
Fluorescence is widespread in mammals, including the domestic cat species (Felis catus), report experts at Curtin University in Perth, Australia (file photo)
Researchers found clear evidence of fluorescence in the white fur, spines and even the skin and nails of koalas, Tasmanian devils, short-beaked echidnas, southern hairy wombats, quendas (bandicoots), greater bilbies and even cats
Recently, several mammals have been reported to ‘glow’ with fluorescence under UV light, including Australia’s beloved platypus.
Experts already knew that bones and teeth glow, just like white human hairs and nails, but until now no one knew how often this occurs in mammals.
The new study, led by Dr Kenny J. Travouillon, palaeontologist at the Western Australian Museum in Perth, now confirms ‘widespread mammalian fluorescence’.
“Almost every mammal we studied showed some form of fluorescence,” he said in a piece for The conversation.
‘We think that fluorescence is very common in mammals; in fact, it’s probably the default status of hair unless it’s heavily pigmented.”
It may be that fluorescence evolved in animals as a useful biological function, for example for communication for nocturnal species, although this is not certain.
“It may simply be an artifact of the structural properties of unpigmented hair,” said Dr. Travouillon.
Preserved wombats glowing under UV light (photo). Those that are alive or newly dead may even still be fluorescent
Fluorescence spectra for frozen specimens of the domestic cat species (Felis catus). The cat’s dark fur was not fluorescent, but the white fur was
Image shows fluorescence for preserved and frozen specimens of platypus (a), koala (b) and Tasmanian devil (c). Photo shows frozen specimens under UV light, using a filter
‘However, we suggest that fluorescence may be important for brightening light-colored parts of animals used as visual cues.
‘This could improve their visibility, especially in low light – much like the fluorescent optical brighteners added to white paper and clothing.’
Dr. Travouillon and colleagues studied preserved and frozen specimens from museums and wildlife parks, including the Western Australian Museum and the Tasmanian Museum and Art Gallery.
The researchers started with the platypus to see if they could replicate the previously reported fluorescence another survey in 2020.
At the time, the fur of all three platypuses was uniformly brown under visible light, but under UV light they appeared green or cyan.
‘We photographed preserved and frozen platypuses under UV light and observed a fluorescent (although quite faint) glow,’ said Dr Travouillon.
They then used a technique called fluorescence spectroscopy – which shines different light sources on the samples and records the specific ‘fingerprints’ of the glow – to confirm that what they saw was indeed fluorescence.
After repeating this process for other mammals, they found clear evidence of fluorescence in koalas, Tasmanian devils, short-beaked echidnas, southern hairy wombats, bandicoots, greater bilbies and even cats.
Orange leaf-nosed bat under UV light. The Australian species dwells in caves, eats moths and is sensitive to human intrusion
Areas of fluorescence include white and light fur, spines, whiskers, claws, teeth and some bare skin.
In the domestic cat, the dark fur was not fluorescent, but the white fur was, with a similar intensity to that of the platypus.
The team admits that they have studied preserved animals that have been long dead, but animals that are alive or recently dead can be even more fluorescent.
“We would suggest that further research should focus on non-preserved animals,” they conclude in their article, published in the journal Royal Society Open Science.
‘These would not be affected by possible degradation of fluorescent materials or by preservation chemicals.
‘Species of interest include species with highly patterned coats, which may be important for visual signaling or camouflage, and species with highly specialized life histories.’