Immense World: Reading Notes (3)

(Burrowing Owl Update Below)

In Chapter 7, Yong takes on surface vibrations.  They aren’t sound, because they don’t travel through air or water, and ears can’t hear them, but creatures can feel them. Frog embryos in the egg can sense the vibrations of an attacking snake.  Treehoppers, leafhoppers, cicadas, crickets and hundreds of thousands of other species  communicate by making and sensing vibrations, yet scientists have largely ignored them.  The first scientists used simple contact microphones from Radio Shack to hear the vibratory concerts of treehoppers.  Newer tools like lasers reflect the vibrations and convert them to sound. Some treehoppers sound like birds, apes, machinery, musical instruments, monkeys, backup signals, drums, cows in pain, chainsaws….  Scientists have whole libraries of their sounds. Among other animals that rely on subtle vibrations are sand scorpions.  So do ant lions.  Worms surface at the vibrations of a digging mole, and gulls and turtles exploit this, as do fisherpeople, by rattling the ground. Felines of all sizes have vibration-sensor cells on the skin of their bellies.  Crouching low may be more than resting. It may be sensing vibrations made by prey. The biggest land users of vibrations are elephants.  They can pick up vibrations of distant animals with their feet. The Indigenous people of America sat on the earth in order to pick up on its vibrations.  Many of those are now silenced.  The prairies used to rumble with the hooves of masses of buffalos, now killed by settlers in an effort to starve the people who depended on them.  A special case of relying on vibrations are the web-spinning spiders. Their webs are extensions of their nervous system, and even though their eyesight may be very poor, they can tell exactly where and what is tangled in their web. Other bugs can exploit this quality to catch and kill the spider.   

Then we move into Sound (Chapter 8).  Exhibit 1: the barn owl.  Scientists demonstrated that a barn owl can accurately and quickly catch a mouse in a room so completely dark that even the owl cannot see.  It located the prey’s rustling among leaves on the ground with its ears alone.  The left ear is placed higher than the right, so that the bird can spot the target not only in side-to-side stereo but also on the up-and-down axis. The owl is also able to tune out the noise of its own wingbeats.  Mice can’t hear those wingbeats, but kangaroo rats can, and owls have a lot of trouble catching them. While most mammal ears are basically the same, insects may hear with a bewildering variety of ears and similar sound-catching organs. Many insects don’t hear at all. So statistically, since insects outnumber everybody else, it probably follows that most animals are deaf, and do just fine with it. Who needs sound anyway?  Well, many butterflies do, so they evolved ears on their wings that are tuned to the wingbeats of predatory birds. And crickets need to find each other to mate, so they evolved ways of chirping and of listening to chirps with ears on their legs.  And a parasitic fly, Ormia ochracea, developed ears to hear that chirping so as to deposit maggots on the cricket and eat it. Its ears are more accurate in locating a chirping cricket than the barn owl with mice.  Tungara frog males make whining sounds often followed by short chucks.  Females prefer males who chuck a lot.  Unfortunately so do the local bats. The male who chucks a lot is highly liable to become bat lunch.   Among the biggest recent discoveries in animal hearing concerns birdsong. It turns out that birds can both make and hear extremely fast variations in a note, inaudible to human ears. The musical notes we hear are just a carrier tone.  The message is not in the melody but in the microstructure, which could convey data about sex, health, identity, intention, and more. Similar breakthroughs were made in the study of hearing under water.  Sound travels faster and much longer distances in water than in air.  Through recordings of whale songs, including sounds below the range of human hearing, researchers were able to demonstrate that blue whale calls traveled 1,500 miles or more. There is evidence that whales may communicate with one another over such distances, and that they use their calls and their echoes to map the ocean floor and navigate long distances, as they do.  On land, elephants make sounds below human hearing to communicate with one another. Other species, including mice, rats, and some others, communicate at frequencies above human hearing. Researchers have kept rats and mice in laboratories for centuries without ever realizing that the animals were constantly communicating with one another.   

This leads directly into Ch. 9: Echoes.  It’s largely the story of bats, and how humans struggled to catch on to the fact that they issued ultrasonic noises and listened to the echoes. Hunting small flying insects in the dark using echolocation is damnably difficult.  Different bats do it in different ways.  Yong describes the decades of research that have gone into unraveling these puzzles.  Bats aren’t the only animals that use echolocation.  Dolphins do it too.  The US Navy recruited dolphins for military tasks and to try to create sonar equipment that worked the same way. Although sonar electronics now exist, nothing can match dolphins’ ability.  They can find items such as mines buried under several feet of sediment and tell whether the items were made of brass or steel.  Porpoises, belugas, narwhals, sperm whales and orcas also echolocate as skillfully as dolphins. It is very strange that they are able to issue sounds and hear them, given their very unbatlike anatomy, but they perform feats of echolocation in water that no bat could achieve in air. Dolphins can sense not only the outside shape but the inner structure of living things, such as their organs, as if they had x-ray vision. There are even people who use echolocation, such as Daniel Kish, blind from infancy, who learned to get around by making clicking noises and listening to the echoes.   

This takes us to Ch. 10, “Living Batteries,” which starts out about electric fish.  Some 350 species of them generate electricity, ranging from the 7-foot electric eel that can stun a horse to the myriad elephantfishes of Africa and the knifefishes of South America, most of them about the size of a human hand, and among the most common fishes in their habitats.  Their electric fields are too weak for a human to feel. But the fish feel them, thanks to tens of thousands of electric sensors all over their skins. The fish send out electric charges much like bats and dolphins send out sounds, and “listen” to — or “feel” — the disturbances in the field that surrounding objects generate.  Many species also use electric discharges to communicate with one another. The species that generate electric fields are vastly outnumbered by those that only sense them, starting with the sharks.  They will dig furiously in the sand to expose electrodes buried by experimenters. All living bodies in water create electric fields. They are extremely feeble, but sharks, rays, and many other species can detect them in close proximity. But fish aren’t the only ones.  It turns out that bees can sense the electric fields around flowers. Some spiders can do the same, and many other bugs show sensitivity to static electricity. This is one of the frontiers of current research.  

Evidence has been piling up for decades that animals can sense the earth’s magnetic field.  That’s the topic of Chapter 11.  It turns out that certain Australian moths use the magnetic field for their annual navigation.  So apparently do sea turtles, spiny lobsters, songbirds, and many others, possibly including whales. This is one of the most controversial issues in current science, mainly because scientists are baffled by how the animals could possibly do it.  Their brains don’t contain tiny magnets. The trending theory involves quantum physics.  I’ve mentioned it here previously, see “Quantum Magnets in Birds’ Eyes” Apr 7 2022. If it’s corroborated — and it’s gaining strength with every new experiment — it suggests that birds may actually see the magnetic field. A Nobel Prize may await the team that finally nails down how magnetoreception works.   

In the concluding two chapters, Yong makes two basic points.  First, although the book has been analyzing senses one by one, no animal relies on one sense alone.  They all use them in some combination all the time.  Secondly, now that we know about the immensity of the sensory worlds that exist, we have an obligation of stewardship to preserve them.  We live in the Anthropocene, and we’ve been brutal to animal species and their sensory worlds.  We pollute the darkness, we noise out the silence, we poison the air and vandalize the water, we replace indigenous species with noxious invasive ones, we heat the climate beyond tolerance for many species.  We live in an era of biological annihilation comparable to the great mass extinctions of prehistory. Only disasters that strike humans, such as the current pandemic, give nature a bit of a break.  Yong salutes small-scale efforts to mitigate the harm to species, such as reductions in night lighting, but, he says “To truly make a dent in sensory pollution, bigger steps are needed.”  

Ed Yong’s An Immense World: How Animal Senses Reveal the Hidden Realms Around Us is available through your favorite bookseller.

Burrowing Owl Update

Burrowing Owl (Athene cunicularia) Dec. 10 2022

Due to the stormy weather and the Morocco-Portugal game (Yay!) I didn’t get to the park until midday. The Burrowing Owl had switched from its yesterday perch back to Perch B again, which meant I could easily see it from the paved perimeter trail. It stood out completely exposed, as usual on rainy days. It didn’t look to me like it was enjoying the shower — how do you read an owl’s facial expression? But it certainly had the choice to duck down into one of the many caves between the boulders below its feet, and it selected to stand in the rain. Except for one moment when it looked like the wind was pushing it off balance and it briefly extended its other foot, the bird seemed relaxed and alert. During the brief minutes that I filmed it, nothing exceptional took place.

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One thought on “Immense World: Reading Notes (3)

  • Thanks I appreciate your detailed synopsis! I will try to check it out of the library. I’m saving links to your 3 synopses since I forget half of what I read. Ed Yong did a phenomenal amount of research. I recently read a very interesting book on the animal kingdom which was mind-blowing in many ways, but bare-bones of necessity (tiny – one of the Oxford university press’s “very short introductions” rather small print but exceedingly well-written, and literally fits in a pocket, great for BART). This book on the variations of animal senses looks like it will be a mind-blowing next read.

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