Infrared antenna-like structures in mammalian fur

Mammalian fur is a highly adaptable structure, with a broad range of well-documented functions. Many small animals, including shrews, most rodents, and some marsupials, have fur composed of at least four types of hair, all with distinctive and complex anatomy. A ubiquitous and unexplained feature is periodic, internal banding with spacing in the 6–12 μm range that hints at an underlying infrared function. One bristle-like form, called guard hair, has the correct shape and internal periodic patterns to function as an infrared antenna. Optical analysis of guard hair from rodents, shrews and antechinus shows precise tuning to the optimum wavelength for thermal imaging. An infrared sensory capability, that provides all-round infrared threat-warning, could explain why common predators of rodents, such as, small cats, snakes and owls have adaptations to conceal their infrared emission. There are many other well-recognised infrared sensors in members of the Reptilia, Insecta, Arachnida, and Ma...