An Immense World by Ed Yong

An Immense World by Ed Yong is a captivating exploration into the intricate and diverse ways by which animals perceive the world around them. It takes a deep dive into the rich tapestry of the animal kingdom and sheds light on how their senses reveal a vastly different reality from what we, as humans, perceive as the "Real World."

Indeed we should refrain from imposing our limited perception of reality onto animals. As humans, we perceive the world through our own subjective lens, influenced by our senses and cognitive skills. The World, as humans experience it, is simply just one of the many different ways of perceiving the world.

Ed Yong's vivid descriptions of animals and their various sense organs are so enchanting that I simply had to google and search for the images and videos to fully comprehend what was being described.

The book covers a wide range of captivating topics, and I will just try to highlight a few of the fascinating images and visuals that have been imprinted on my mind. Have also posted links to videos wherever I could find it.

Ants- Pheromones 

The book begins by delving into the fascinating world of Pheromones. Compared to humans, Ants are nearly blind and deaf. An Ant's main mode of communication is through smelling chemical agents called pheromones.

Pheromones are Lightweight chemicals that easily rise into the air and are used to summon mobs of workers that can rapidly overwhelm prey. Crush the head of an ant, and within seconds, nearby colony-mates will sense the aerosolized pheromones and charge into battle.

Pheromones are also used to mark trails. The Ant Workers lay these down when they find food, leading other colony-mates to foraging hotspots. Other Pheromones are also found on the surface of the ants' bodies, and act as identity badges.

Pheromones hold such sway over ants that they can force the insects to behave in bizarre and detrimental ways, in disregard of other pertinent sensory cues. Red ants will look after the caterpillars of blue butterflies, which look nothing like ant grubs but smell exactly like them. The YouTube link shared below captures what the author so vividly describes in the book:-

 Army ants are so committed to following their pheromone trails that if those paths should accidentally loop back onto themselves, hundreds of workers will walk in an endless "death spiral" until they die from exhaustion.

Many ants use pheromones to discern dead individuals: In an experiment, when oleic acid was daubed onto the bodies of living ants, their sisters treated them as corpses and carried them to the colony's garbage piles. It didn't matter that the ant was alive and visibly kicking. What mattered was that it smelled dead.

Colors

One of the most intriguing chapters is the one which discusses color perception, highlighting the variations among different species. Human beings are trichromats, and most people can match any given reference color by combining the three primary colors. However a small proportion of people, and entire species of animals,  see only in shades of gray, not because of brain damage but because their retinas aren't set up for color vision. They are called monochromats.

Whales have just one cone. So for a Blue Whale, the ocean is not blue. Octopuses are also monochromats. So they can rapidly change the colors of their skin , yet are unable to see their own shifting hues.

Dogs have two cones and are dichromats. They see mostly in shades of blue, yellow, and gray.  Below is a photo reproduced from the book on how dogs view the world:

This YouTube video covers how most animals perceive the world around them:-

 

Birds can perceive colors humans can't. Most birds have four types of cone cells, and are hence tetrachromats. So they are able to distinguish a multitude of colors that are imperceptible to us.

Dichromats can make out roughly One percent of the colors that trichromats see i.e. tens of thousands, compared to millions. If the same gulf exists between trichromats and tetrachromats, then we might be able to see just I percent of the hundreds of millions of colors that a bird can discriminate. 

Birds  don't just have human vision plus ultraviolet, or bee vision plus red. Tetrachromacy doesn't just widen the visible spectrum at its margins. It unlocks an entirely new dimension of colors.

Frustrating though it might be, most of us simply cannot imagine what many animals actually look like to each other, or how varied their sense of color can be.

All of us- monochromat, dichromat, trichromat, or tetrachromat- -take the colors that we see for granted. Each of us remain convinced that this is what the world is really like.

 Heat sensing Beetles

Fire-sensing beetles have an outer skin tough enough to let them sense the infrared radiation from a blaze up to 10 kilometers away. Arriving at a fire, the beetles have perhaps the most dramatic sex in the animal kingdom, mating as a forest burns around them. Later, the females lay their eggs on charred, cooled bark. When the wood-eating grubs hatch, they find an Eden. The trees they devour are too injured to defend against insect larvae feeding within them. The predators that might eat them are put off by the smoke and heat emitted from the embers and ashes. In peace, they thrive, mature, and eventually fly off in search of their own blazes

Parasite Animals

The emerald jewel wasp is a parasite that raises its young on cockroaches. When a female finds a roach, she stings it twice once in its midsection to temporarily paralyze its legs, and a second time in its brain. The second sting delivers venom that nullifies the roach's desire to move, turning it into a submissive zombie. In this state, the wasp can lead the roach to her lair by its antennae, like a human walking a dog. Once there, she lays an egg on it, providing her future larva with a docile source of fresh meat.

 

Tadpoles- Surface Vibrations

When a cat-eyed snake lunges at a tree frog and clutch and grabs several eggs in its jaws, the surrounding embryos wriggle furiously, releasing an enzyme from their faces that quickly disintegrates their eggs. One of them plops into the water. A second later, another joins it. Soon, tadpoles are tumbling down too quickly to count, and the snake, still chewing its first mouthful, is left with a smear of empty jelly.

 

Thus frog embryos sensory bubble extends beyond the actual bubble in which they're trapped. Light can pass through the translucent eggs, and chemicals can diffuse into them. But vibrations are what really matter. They pass into the eggs and into the embryos, which can distinguish between bad vibes and benign ones without any previous experience of either. A bite from a snake will trigger hatching. Rain, wind, and footsteps will not. 

Treehoppers, which are pea-sized insects communicate with each other using jiggles. By rapidly bouncing their abdomens, they send vibrations down through their legs and into the plant they are standing on. Nearby treehoppers pick up and interpret the vibrations, which vary in frequency and pattern depending on the message being conveyed.

The songs that Treehoppers make are haunting, mesmerizing, and surprising. None of them sound remotely like the familiar, high pitched chirping of crickets or cicadas, but instead sound more like birds, apes, or even machinery and musical instruments.

 

Owls

As Owls are generally active at night, they have a highly developed auditory system. The ears are located at the sides of the head, behind the eyes, and are covered by the feathers of the facial disc. But while a humans outer ears are a pair of fleshy flaps, the owl's are effectively its entire face.

They act like a radar dish that collects incoming sound waves and funnels them toward the ear holes. These enormous openings are found behind the owl's eyes, hidden among its feathers. In some species, they're so wide that if you part the overlying feathers and look into the ears, you can see the back of the owl's eyeball.

 

Bats

Bats produce echolocation by emitting high frequency sound pulses through their mouth or nose and listening to the echo. With this echo, the bat can determine the size, shape and texture of objects in its environment. Bats have developed the most specialized form of sonar in the world.

Many night-flying insects hear the sonar sounds of attacking bats and take evasive action. Among moths, evasive flight is often accompanied by the production of ultrasonic sounds. The Ultrasonic counter clicks either startle the bat, to warn of distastefulness, or “jam” the bat's sonar system.

Tiger moths click to tell bats that they aren't worth eating and that they are full of foul-tasting chemicals.

American tiger moths frequently flub attacks by 'jamming' the Bats' Sonar System. The clicks by the Moths overlapped with the bats' echoes and messed with their ability to gauge distance.

Electric eels.

The Eels electric organs take up most of their 7-foot-long bodies, and contain around 100 stacks of between 5,000 and 10,000 electrocytes. The most powerful of the electric eel species can discharge 860 volts enough to incapacitate a horse. When hunting small fish and invertebrates, it delivers pulses that force the muscles of its prey to twitch, giving away its position. Stronger pulses then cause those same muscles to lock, paralyzing the victim. The electric organ is both remote control and Taser, allowing the eel to commandeer the bodies of other animals from afar.

Magnetic Fields

 The geomagnetic field of the Earth is a boon for travelers, who have always used it to establish their bearings. Humans have done so for more than a thousand years, using compasses. Other animals sea turtles, lobsters, birds – have done so for millions of years without help.

Whales have some of the most insane migrations of any animals on the planet. Some of them almost go from the equator to the poles, and with astounding precision, traveling to the exact same area year after year. And it is suggested that they have inbuilt gyro compasses.

"An Immense World" is a truly exceptional read. The book is indeed a riveting journey into the awe-inspiring world of animals and their extraordinary senses.