Bats, I've even suggested, use perceived hues, such as red and blue, as labels, internal labels, for some useful aspect of echoes -- perhaps the acoustic texture of surfaces, furry or smooth and so on -- in the same way as swallows or indeed, we, use those perceived hues -- redness and blueness, etc. -- to label long and short wavelengths of light.
Morcegos, eu sugeri, utilizam cores, como vermelho e azul, como rótulos internos para algum aspecto útil dos ecos -- talvez a textura acústica das superfícies, peluda ou lisa, da mesma maneira que as andorinhas, ou, de fato, nós, usamos as cores -- vermelho, azul, etc. -- para rotular os comprimentos de onda.