Birds of prey boast the greatest visual acuity of all animals and zoologists believe some hawks and eagles have vision eight times sharper than ours. An eagle’s retina sports approximately 1 million sensory cells per square millimetre – around five times what you’d find in a human retina. It pays off: some birds of prey can spot and track a rabbit 1.5 kilometres (0.9 miles) away! If you gauge eyesight in terms of light spectrum perception instead of acuity, the mantis shrimp is the champ. Mantis shrimp perceive 11 or 12 primary colours, putting our three to shame, and they see ultraviolet and infrared light too. But their greatest trick is the ability to perceive both linear polarisation and circular polarisation of light, a talent no other animal possesses.
Answered by Tom Harris.