Is polar bear hair fiber optic?

New direct measurement of high optical attenuation rates in polar bear hairs--2-8 dB/mm in the visible--and reanalysis of the data of Tributsch et al. [Sol. Energy Mater. 21, 219 (1990)] seem to rule out the UV waveguiding proposed by Grojean et al. [Appl. Opt. 19, 339 (1980)]. The case against fiber-optic polar bear hairs is summarized, and four conditions are given that any variation of the model of Grojean et al. would have to satisfy.