Martin Stevens - Secret Worlds: The Extraordinary Senses of Animals

The philosopher Thomas Nagel once posed the question What is it like to be a bat? in a thought experiment about perception and consciousness. In doing so, he was really asking questions about what consciousness means, but we might equally pose the same question to think about what the sensory world of a bat is like and how that governs its life. It is easy to fall into the trap of assuming that other animals perceive the world in the same way that we do, but the reality could hardly be more different, or exciting. What we perceive are but snapshots of the physical world, measured and interpreted by our senses and our brain. The product of our evolutionary past, our senses only allow us to perceive those aspects of the world for which we have the necessary apparatus, used to gather the information we needed to survive.

Far from being uniform across species, how an animal perceives the world is heavily dependent on its sensory systems and brain. In the case of bats, many species have a highly sophisticated ability to use echolocation to navigate and hunt for prey. This is centred on ultrasonic frequencies that operate well above our hearing range. Our ears are simply not tuned to detect these frequencies. Each animals perception of the world is therefore a product of its sensory systems, and the information detected can differ greatly from other species.

Its worth pausing for a moment to consider how crucial our senses are to everything we do. Vision, smell, taste, hearing, and touch all provide us with an essential ability to respond to threats, communicate with one another, perform numerous daily tasks, avoid obstacles, and interact appropriately with the world around us. To people who have lost just one of their main senses, such as vision, many tasks the rest of us take for granted can be challenging. So, imagine what life would be like if we lost our vision, our hearing, our smell and taste, our touch, and so on. Our senses provide a critical gateway to the outside world, allowing us to interact with it. The same is true for all animalstheir sensory systems are what enables them to forage, avoid predators, attract mates, navigate, and much more. Without them, individuals would be completely helpless.

Human senses do a reasonable job of allowing us to gather information from the world and behave accordingly. But throughout this book we will encounter many animals with senses that, in comparison to ours, seem extremely refined. By contrast, we are more of a jack of many trades, with a range of good but not spectacular senses. I say many rather than all trades because we lack entirely some sensory systems that other animals possess. Ultimately, the sensory systems of other animals are tuned to widely different stimuli. For example, many animals, from spiders to birds, can detect and respond to ultraviolet light, to which we are blind. Others, including numerous insects, rodents, and bats, can hear high-frequency ultrasonic sounds well beyond our own hearing range.