12. Vision and Sensory Evolution
Sloths’ sensory systems have evolved remarkably to fit their particular way of existence. Their vision has evolved to efficiently operate in both bright and low light environments, with specific rod and cone configurations that improve their capacity to detect movement while energy is being conserved. Unlike most mammals, they have evolved limited colour vision and instead concentrate on pattern recognition that guides their assessment of leaf quality and predator identification. Their eyes have evolved unusual structural modifications that enable them to see clearly while hanging upside down; specialised muscles keep their eyeballs from rolling when inverted. Visual information’s brain processing has changed to give vital survival cues top priority and minimise non-critical visual processing energy use.