Photoluminescence in mammal fur: 111 years of research

Abstract

Photoluminescence in the pelage of mammals, a topic that has gained considerable recent research interest, was first documented in the 1700s and reported sporadically in the literature over the last century. The first detailed species accounts were of rabbits and humans, published 111 years ago in 1911. Recent studies have largely overlooked this earlier research into photoluminescent mammalian taxa and their luminophores. Here we provide a comprehensive update on existing research on photoluminescence in mammal fur, with the intention of drawing attention to earlier pioneering research in this field. We provide an overview on appropriate terminology, explain the physics of photoluminescence, and explore pigmentation and the ubiquitous photoluminescence of animal tissues, before touching on the emerging debate regarding visual function. We then provide a chronological account of research into mammalian fur photoluminescence, from the earliest discoveries and identification of luminophores to the most recent studies. While all mammal fur is likely to have a general low-level photoluminescence due to the presence of the protein keratin, fur glows luminously under ultraviolet light if it contains significant concentrations of tryptophan metabolites or porphyrins. Finally, we briefly discuss issues associated with preserved museum specimens in studies of photoluminescence. The study of mammal fur photoluminescence has a substantial history, which provides a broad foundation on which future studies can be grounded.

Does the photoluminescence of rat fur influence interactions in the field?

“…Our predictions were based on the ability to observe blueish-white photoluminescence either being ubiquitous to mammals or being species-specific. The expression of photoluminescence in mammal fur is common (Reinhold et al 2023). Of the 16 wild mammal species identified in this study, the 10 that have also been examined with ultravioletviolet light all display fur photoluminescence (either pink and/or blueish-white) to some degree (Reinhold 2021(Reinhold , 2023.…”

Ultrasound and ultraviolet: crypsis in gliding mammals

“…2 ). We encourage researchers with access to other mammalian gliders (particularly giant flying squirrels, colugos, and marsupial gliders) to assess UVP with live specimens to either confirm a lack of UVP or to challenge our findings ( Reinhold et al, 2023 ). We also note that the pelt preservation processes are unknown in the species used and there is a possibility that we have detected false positives due to chemicals and not natural photoluminescence, particularly in the mounted Sicista subtilis.…”

“…Several researchers have proposed that porphyrin induced UVP in fur should be highly associated with nocturnality ( Kohler et al, 2019 ; Olson et al, 2021 ; Toussaint et al, 2023 ). Specifically, porphyrins and tryptophan metabolites, which readily accumulate in mammalian fur through various physiological pathways, have been identified as the main compounds associated with UVP in mammal pelage ( Toussaint et al, 2023 ; Reinhold et al, 2023 ). Some of these luminophores are easily degraded by UV rays emitted by the sun ( e.g.…”

“…While “white” UVP has been noted in some species, this “white” coloration has been reported as a bluish-white (as seen in the striped possum ( Dactylopsila trivirgata ) and some marsupial gliders; Reinhold, 2021 ). The underlying cause of UVP expressed as distinct colors have been linked to porphyrins (red or pink) or tryptophan metabolites (cyan, blue, lavender; Reinhold et al, 2023 ). However, the expression of exclusively “white” coloration is not commonly reported, nor has a clear explanation been proposed for producing UVP without a dominant color.…”

“…Flying squirrels have been shown to exhibit another unique trait: ultraviolet-induced photoluminescence (UVP) in fur ( Kohler et al, 2019 ; Reinhold et al, 2023 ; Toussaint et al, 2023 ). Recent interest in this topic has led to the discovery of UVP in several species, including other gliding mammals ( Reinhold, 2021 ) and relatives, such as springhares ( Olson et al, 2021 ; shared suborder with scaly-tailed flying squirrels) and dormice ( Nummert, Ritson & Nemvalts, 2023 ; shared suborder with flying squirrels).…”