An Immense World: How Animal Senses Reveal the Hidden Realms Around Us

By Ed Yong, Random House 2022

Book reviewed by Nell Marshall

An Immense World explores the world of animal senses and perception. This world, as perceived and experienced through the senses, Yong calls the Umvelt. Our environment, or any animal’s environment as perceived through that animal’s senses. The Umvelt, the world each animal perceives, is accessed through the senses and defined by those perceptions.

The concept of Umvelt that Yong describes is a unifying and leveling force:

“The human’s house might be bigger than the tick’s, with more windows overlooking a wider garden, but we are still stuck inside one, looking out. Our Umwelt is still limited; it just doesn’t feel that way. To us, it feels all-encompassing. It is all that we know, and so we easily mistake it for all there is to know. This is an illusion, and one that every animal shares.”

Our Umvelt, the illusion that all we perceive is all there is to perceive, and the knowledge there are so many different kinds of perception, is useful to keep in mind when practicing qigong, when contemplating meditations, and when considering the accessibility and movement of chi.

Yong writes: 

“senses cannot be clearly divided into a limited number of discrete kinds,” …

“Though I have organized this book into chapters that revolve around specific stimuli, like light or sound, that’s largely for convenience. Each chapter is a gateway into the varied things that animals do with each stimulus. We will not concern ourselves with counting senses, nor talk nonsensically about a ‘sixth sense’.  We will instead ask how animals use their senses and attempt to step inside their Umwelten.”

Humans primary sense is sight.  Consider how we depend on it, and how extensively we use sight and seeing as metaphors for understanding.

As a gardener I am one of many people who have stared into the eyes of a jumping spider and seen an answering intelligence. It’s the eyes. Jumping spiders have four pairs of eyes that can see clear detail of shape and color and also detect and track motion. 

“These tasks—sharp vision and motion detection—feel inseparable. And yet jumping spiders have separated them so thoroughly that they exist within different sets of eyes.

The central ones recognize patterns and shapes and see in color. The secondary ones track movements and redirect attention. Different eyes for different tasks, and each set has its own distinct connections to the spider’s brain.  Jumping spiders remind us that we share a visual reality with other sighted creatures, but we experience it in utterly different ways. We don’t have to look to aliens from other planets, … We have animals that have a completely different interpretation of what the world is right next to us.”

The nose provides a primary window on the world for many animals.  For a dog, going for a walk is a feast of scentscapes. Alternatively, for a bat, their world, their Umvelt, is defined primarily by sound through sonar.  Sea otters and star nosed moles use touch to explore their worlds and locate their meals, but in completely different ways. Yong digs into research on each of these in detail. He notes there is a difference in researching animal senses according to what people find interesting as opposed to what the animals find interesting. 

The elephant’s primary tool for investigating its world is its nose.  When elephants greet each other, they stick their trunks in each other’s mouths. They urinate and defecate, and glands in their temples stream down the sides of their face indicating by smell their emotional state. All these smells provide a picture of their health, age, gender, diet, mood, recent history, and more. Bets Rasmussen, a biochemist working extensively with elephants, their secretions, excretions and smells, speculates:

“elephants might guide their long migrations using ‘chemical memories of landscapes, terrain, pathways, mineral and salt sources, waterholes, the scenting of rain or flooding rivers, and tree odors signifying seasons.’ No one has tested these claims, but they make sense.”

Elephants have long memories, and scents are certainly a major part of those memories.

Where and how do the senses report their findings? How does that shape an animal’s Umvelt? Consider the octopus:

“An octopus’s central nervous system contains around 500 million neurons—a total that dwarfs that of all other invertebrates and that’s comparable to the number found in small mammals. But only a third of these neurons are located in the animal’s head, within the central brain and the adjacent optic lobes that receive information from the eyes. The remaining 320 million are in the arms. Each arm ‘has a large and relatively complete nervous system, which seems barely to communicate with the other arms,’ Robyn Crook once wrote. An octopus effectively has nine brains that have their own agendas.”

Yong delves deeply into a variety of research on animal senses.  He offers many more stories of the senses, so much more than I can feature here. The various studies and experiments Yong observes are imaginative and fascinating.   He talks with leading sensory researchers, describes their experiments and carefully footnotes information in his book. In his first chapter he describes all living beings as leaking sacks of chemicals, of smells and tastes. Throughout the book he discusses light, color, pain, heat and cold, touch and contact and flow, surface vibration, sound, echoes, electric fields, magnetic fields. He writes about uniting the senses and about threatened sensescapes.

The audiobook version of An Immense World makes good listening. It is pleasant to listen to or to read a little bit every day.  There is much to think about in this book and much to imagine.