Supplementary material from "Nanopores in the ventral scales of Bitis rubida and Bitis armata cause white venters"

Recent studies speculated that some snakes developed white venters to avoid overheating caused by highly radiative soil and rocks. Here, we present the scale-embedded porous nanostructures through which some snake species of the genus Bitis achieve such whiteness. Our analysis reveals nanopores causing scattering underneath the external surface of the white ventral scales of Bitis rubida and Bitis armata. Such nanopores are not present in the scales of Bitis parviocula, Bitis arietans, and Bitis rhinoceros that appear transparent or translucent to the naked eye. White ventral scales with nanopores reflect up to 40% of light in the visible regime. The reflection, however, decreases for longer wavelengths and drastically reduces in the infrared. In contrast, a much lower, almost constant reflection around 8% between 250 nm and 2500 nm is observed for the transparent or translucent ventral scales without nanopores. Our study demonstrates that some snake species of the genus Bitis utilize a light scattering network of nanopores underneath their external surfaces to create white ventral scales.