Temporal Change in Fur Color in Museum Specimens of Mammals: Reddish-Brown Species Get Redder with Storage Time

Abstract

Museum collections have great value for zoological research, but despite careful preservation, over time specimens can show subtle changes in color. We examined the effect of storage time on fur color of two reddish-brown species, golden mice (Ochrotomys nuttalli) and eastern chipmunk (Tamias striatus). Using image analysis, we obtained color data (hue, saturation, and density) on 91 golden mice and 49 chipmunks from Georgia, USA. Analyses that considered body size, gender, and collection year showed significant effects of year on fur color of golden mice (hue and saturation) and of agouti color of chipmunks. Older specimens tended to be redder in color than newer specimens, consistent with a prior study of red bats (Lasiurus borealis). Hair samples showed reddening of fine body hairs, but not in thicker guard hairs. There was no temporal change in black or white stripe color in chipmunks, indicating that this temporal effect would be limited to species with reddish-brown fur. This effect may be caused by breakdown of eumelanin pigments (which make dark colors) over time, leaving a greater proportion of pheomelanin pigments (which make red colors). These results show that storage time needs to be considered in research projects where fur color is of importance.

Spectral Reflectance of Polar Bear and Other Large Arctic Mammal Pelts; Potential Applications to Remote Sensing Surveys

“…The process of preserving and tanning pelts can affect the color and thus the reflectance patterns of fur [32]. Similarly, fur color in museum specimens can change over time [33]. The time of year of collection could also affect fur color with, for example, The applicability of these results to remote sensing surveys depends on a number of factors including the similarity of our pelt measurements to those of live animals, the spectral reflectance patterns of the background and other environmental contaminants, and the availability of appropriate sensors.…”

“…The process of preserving and tanning pelts can affect the color and thus the reflectance patterns of fur [32]. Similarly, fur color in museum specimens can change over time [33]. The time of year of collection could also affect fur color with, for example, freshly molted polar bear fur tending to appear whiter and less yellowish [34].…”

“…The observed differences in reflectance in the infrared between the juvenile and adult polar bear pelts (Figure 3) could potentially be due to differences in freshness, wear or treatment of the fur, rather than age differences per se. Nevertheless, most reported impacts of preservatives or aging on color of mammal pelts relate to reddening of dark colors ("foxing"), which would not affect polar bears [32,33]. Although white colors could obviously become stained, the general color and pattern of all of the pelts, at least in the visual range, appeared to fit within the range of variation observed in live animals, although the polar bear pelts were darker than some, and some of the seal pelts appeared to be slightly foxed or stained with oils.…”

Intra-specific pelage color variation in a South American small rodent species

“…In specimens of the same taxonomic unit, variations in coat color may exist in relation to several biological features, such as age (e.g., Rios and Álvarez-Castañeda, 2012), sex (e.g., Davis and Castleberry, 2010;Rios and Álvarez-Castañeda, 2012), season (e.g., Camargo et al, 2006), habitat (e.g., Heth et al, 1988;Carraway and Verts, 2002;Lai et al, 2008;Rios and Álvarez-Castañeda, 2012), etc. Moreover, in specimens collected in different years, there may be variations in coat color in relation to sample antiquity, i.e., the storage time of the specimens in a Mammalian Collection of a Natural History Museum (e.g., Davis and Castleberry, 2010;Davis et al, 2013).…”

The effects of ultraviolet and visible light on common furs: Color changes, photooxidation and the use of Tinuvin 292 as a photoprotectant

“…These limited results show that brown furs, which can be hypothesized to contain relatively similar ratios of melanin and eumelanin, nevertheless can display very different and complex light-induced color changes, perhaps indicative of multiple reactions. Indeed, a recent report suggests that eumelanin pigments in mammalian fur are overall less stable than pheomelanin, resulting in reddening of the furs even in dark storage (Davis et al 2013). In 2011, Ford and Smith included reports on the lightfastness of dingo, possum, wombat, platypus, thylacine, and kangaroo fur as part of their microfade testing (MFT) of indigenous objects at the National Museum of Australia (Ford and Smith 2011).…”