Largest biofluorescent mammal

The largest naturally occurring biofluorescent mammal currently known is the common (aka bare-nosed) wombat (Vombatus ursinus), one of Australia's three species of herbivorous bear-like marsupial known as wombats. It measures up to 1.3 m (4 ft 3 in) long, and weighs up to 40 kg (88 lb). This wombat species was first found to be biofluorescent in November 2020, when, following the then recent announcement that the platypus (Ornithorhynchus anatinus) was biofluorescent, researchers at the Western Australian Museum shone ultraviolet (UV) light, invisible to human eyes, onto various taxiderm specimens and preserved skins of mammals in the museum's collection, and found to their great surprise that several different marsupial species biofluoresced. The largest of these species was the common wombat, whose entire body glowed blue. The invisible UV light was being absorbed by its fur and then re-emitted as visible blue light, which has a longer wavelength and shorter frequency than UV light. Interestingly, neither of the two species of hairy-nosed wombat (genus Lasiorhinus) was found to biofluoresce.

Several other types of marsupial are also known to be wholly or selectively biofluorescent, including in Australia certain species of possums, marsupial mice (Antechinus spp.), the rabbit-eared bandicoot or bilby (whose ears and long snout glow variously orange and green in UV light), and the Tasmanian devil (its eyes, ears, and snout glow blue).

Moreover, some New World marsupials are also biofluorescent, including several South American didelphid opossum species and the most familiar didelphid species of all, the North American or Virginia opossum (Didelphis virginiana) – the very first mammal of any kind that was found to be biofluorescent (it glows bright pink under ultraviolet light).

As yet, the reason for this phenomenon in these mammals is unclear, but as they are all crepuscular by lifestyle, it may be related to recognition of other creatures in the dark, though it has yet to be determined whether or not these mammals can actually discern UV light.