Every year, more and more discoveries of photoluminescence in different mammal species are made. The more recent cases thus far have been in duck-billed platypus (Ornithorhyncus anatinus), New World squirrels (Glaucomys spp.) and springhare (Pedetidae). Now we can add another species to the list: the garden dormouse (Eliomys quercinus) […]"

Source : Photoluminescence in the Garden dormouse (Eliomys quercinus) Zoology, Volume 157, April 2023,

As well as mammals, many other species of fish, molluscs and insects etc. have been found to be strongly fluorescent under UV light. The effect is so strong that entomologists routinely use UV lamps to find arthropods etc.

It's not known why some organisms are ' photoluminescent'.

Theories include the possibility that :

• 'Whole bodies' could be acting as 'photon detectors' in order to find shelter.
• Or that it's involved in some types of communication.
• Or acting as camouflage
• Other research groups suggest that it's just a byproduct of physiological processes and has no specific function.