Epidermal nanostructures enhance thermoregulation in alpine lizards by reducing near-infrared reflectance

Ectothermic survival on the Tibetan Plateau, one of the most thermally challenging terrestrial environments, requires effective heat acquisition, yet the physiological and structural mechanisms enabling thermoregulation at high altitudes remain poorly resolved. Here, we demonstrated that high-altitude lizards warmed significantly faster than lowland relatives and showed reduced skin reflectance in both the visible and near-infrared spectra. Morphological examination identified two major adaptations: elevated melanin accumulation that reduced visible light reflectance, and thickened epidermal layers embedded with nanostructures that suppresses near-infrared reflectance through broadband anti-reflective effects consistent with effective medium theory in physical optics. As near-infrared wavelengths lie beyond the visual sensitivity of most predators, these adaptations likely represent an evolutionary strategy to amplify solar radiation uptake without increasing visual conspicuousness. These features may also reduce radiative heat loss and improve thermal insulation. This study not only identifies a previously unrecognized nanophotonic adaptation for near-infrared absorption in vertebrate skin, but also provides a functional template for the design of bioinspired thermal management materials.