“The glossy sheen of healthy hair is an ideal of human beauty; however, glossiness has never been quantified in the context of non-human animal signaling. Glossiness, the specular reflectance characteristic of polished surfaces, has the potential to act as a signal of quality because it depends upon material integrity and cleanliness.”
For those reasons, Matthew Toomey and colleagues at the School of Life Sciences, Arizona State University have developed – ‘A novel method for quantifying the glossiness of animals’. Their paper on the subject was published in Behavioral Ecology and Sociobiology, May 2010, Volume 64, Issue 6, pp 1047-1055.
A full version of the paper may be found here.
Note: The photo shows measurements of the relative glossiness of a great-tailed grackle.
Also see: ‘Hmmm, sooo shiny, sooo nice’ – but why?