In the opening chapter, Yong introduces the term "Umwelt," used by a German biologist in 1909 to describe how an organism perceives the world around it. It's compared to houses, each with their own unique configuration of windows. Essentially, that there is a variety of sensory information all around us, but not all animals perceive the same aspects, or in the same fashion.
From there, it each chapter focuses on a different type of sense, and the various ways they're expressed by animals. It isn't, as Yong takes pains to stress in the chapter about smell and taste, about how much "stronger" one organism's sense may be than another's. After all, if you say a dog's sense of smell is 5 times greater than a human's, what's that mean? They can smell things five times further away, five times fainter, retain the scent in its absence for five times longer?
No, the point is how they differ, and how this informs the way those animals perceive the world and exist in it. So in the chapter on hearing, Yong notes that not all insects can hear, but that for those that can, the ears are located in almost any location you could conceive of. Often, the location of the ears is related to what specifically they're trying to hear.
Crickets have ears on their legs, and when they detect the call of a potential mate, that information causes the legs to move towards that sound even before the information could be transmitted to the brain. Sharks have their electric sense, via the Ampullae of Lorenzini, and researchers noticed that when an electric current is passed in front of a shark's snout, it blinks. This is because that sense has an limited effective range. It's the one sharks use right before they bite, and sharks take pains to protect their eyes before they bite. The detection of the electric current prompts that response.
Yong talks with a lot of different researchers about a wide variety of animals, covering senses from sight and sound, to the perception of pain or magnetic fields. Different senses are better studied than others - taste was relegated to a half-dozen or so pages at the end of the scent chapter, because not much work's been done with it - while vision got one chapter for sight, and one specifically about seeing color.
Of course, the matter of the other animal's Umwelt is theoretical, because even if we can know that certain insects see ultraviolet light, or that frog embryos can detect the particular vibrational frequency of a snake chewing and begin hatching in response, we can't really know what those things "feel" like for them, because the animals can't tell us. We can chart what section of a bat or dolphin's brain activates when it receives its echolocation information, but do they "see" it in their mind the way that Daredevil does? What does a geomagnetic sense look like?
In that way, the book can only go so far, but I think Yong knew that going in. His point is for us to be more aware that other animals do have very different perspectives of the world, and we can have impacts in ways we don't consider. The last chapter is about the problems of light pollution on insects and migrating birds, noise pollution on songbirds or whales, undersea cables throwing off electric senses. Those things don't seem to hamper us, so we don't consider them, but for creatures who look at the world through different windows, it's a problem.
'If Speiser is right about this bizarre setup, it means that even though each individual scallop eye has good spatial resolution, the animal itself might not have spatial vision. It knows when eyes in a certain region of its body have detected something, but it has no visual image of that object.'
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