Skunks' Warning Stripes Less Prominent Where Predators Are Sparse, Study Finds
Published:04 Jan.2024 Source:University of Bristol
Skunks' iconic black and white colouration signals its toxic anal spray. However some skunks show very varied fur colour ranging from all black to thin or thick black and white bands to all white individuals. Variation is huge across the North American continent. Findings published today in Evolution, suggest that this is a result of relaxed selection, when environmental change eliminates or weakens the selection of a normally important trait -- in this case black and white pelage.
Researcher Hannah Walker from the University of Montana documented the distribution of these different pelage colours across their range in North America using museum specimens. She plotted these against a menu of variables that the team thought might drive this variation in coloration. The team found that in locations in which skunks overlapped with rather few mammalian predators that might be capable of killing them, fur colour was varied even within the same litter. Where there were many species of predators that were a danger to them, they showed little variation.
The results indicate that relaxed predation pressure is key to warning signal variation in this species, whereas stronger pressure leads to signal conformity and stronger signals. Now the team plan to see if this occurs across other skunk species whose geographic ranges overlap in North America. If relaxed selection operates within species, it should do so across prey species too. More broadly, this study provides another brick in the wall of explaining the evolution of coloration in nature.