What enables bats and dolphins to navigate and hunt with such precision in complete darkness? How do animals like sea turtles find their way back to specific beaches across hundreds of miles of ocean?
In An Immense World, Ed Yong explores animal echolocation, electrolocation, and magnetoreception—sensory abilities that help creatures navigate their environment. These extraordinary capabilities reveal how different species experience and interact with their surroundings.
Keep reading to discover how animals use sound, electricity, and magnetic fields to perceive their world in ways humans can barely imagine.
Animal Echolocation
Animal echolocation is a form of hearing in which an animal repeats sounds and listens for the echoes they return. Yong explains that this allows the animal to detect objects as well as to gather detailed information about them. Very few animals have this ability, and only bats and toothed whales (such as dolphins, orcas, and sperm whales) are experts at it.
Bats echolocate by making pulsing sounds with their mouths. They start by emitting loud, infrequent calls and make increasingly faster pulses to gather more information as they zero in on their prey.
Dolphins are so good at echolocation that they can use it to locate buried objects, distinguish between different objects based on size, shape, and material (even up to a difference of only 0.6 millimeters), and even recognize an object visually on a TV screen after using echolocation to find it—without ever having seen it.
(Shortform note: Studies show that echolocation is an even more sophisticated ability than scientists previously thought. For example, a 2024 study demonstrated that in addition to using echolocation to perform short-range tasks such as locating prey and avoiding obstacles, bats can use echolocation to create longer-range mental maps that allow them to navigate over several kilometers. In addition, research attempting to create visual images of what dolphins “see” using echolocation suggests that dolphins can create a 3-D “picture” of a human diver so detailed that they can even make out the diver’s weight belt—all using only sound.)
Animal Electrolocation
Yong writes that just as some animals use echoes to sense their surroundings, others use electricity. There are two types of electrolocation: active and passive.
In active electrolocation, creatures—usually fish—sense objects by sending out electric fields and using electroreceptors on their skin to detect distortions in those fields. Some fish that use active electrolocation are also able to engage in electrocommunication with each other, encoding information such as sex, species, and territory into their electric discharges.
Animals that use passive electrolocation can’t generate electric fields, but they can sense other animals’ electric currents and charges. All animals’ cells produce electric fields when submerged in water. Although these weak currents are generated inside the body, sharks and rays are particularly skilled at detecting them at spots where they’re exposed, such as mouths, gills, or wounds.
(Shortform note: Animals’ ability to use natural electricity predates humans’ ability to generate electricity by millions of years. In fact, the invention of the first battery was inspired by the South American electric eel, a large creature from the Amazon River capable of generating so much electricity (600 volts) that it could cause serious harm to a horse. Italian physicist Alessandro Volta observed the organs of electric eels and came up with the idea of stacking different metals together to generate electricity. Before his invention of the synthetic battery in 1800, the only way for people to generate electricity was by rubbing two materials together to create static electricity.)
Yong says that electric currents need a conductive medium such as water to travel, which is why most electroreceptors are on fish or mammals that live in water. However, some land creatures can also sense electric fields. This is because, due to constant thunderstorms around the globe, the air always carries some electric voltage. Animals such as bumblebees and spiders can sense electric fields using the tiny hairs on their bodies.
(Shortform note: Bees’ ability to sense electric fields may mean that they can predict the weather. One study found that bees spent more time foraging for food outside of the hive on the days before rainy days than they did before dry days. This could be because they sensed atmospheric changes that occur prior to rain or thunderstorms.)
Animal Magnetoreception
Animals with magnetoreception can navigate by sensing the magnetic field created by the Earth’s liquid metal core.
Yong says that magnetoreception allows animals such as birds and moths to migrate extremely long distances without ever having done so before and even in the dark or without smell. Many other animals use magnetoreception to travel distances of every length.
Whales probably use magnetoreception to help them migrate to the same spot every year. Healthy whales that beach themselves for no apparent reason are four times more likely to do so on days with the strongest solar storms (which affect the Earth’s magnetic field). This suggests that whales are also guided by Earth’s magnetic field.
Many animals use magnetoreception to imprint the “signature” of their birthplace so they can find it many years later as adults. Some sea turtles travel hundreds of miles to lay their eggs on the beach where they were born, even though there are much closer beaches they could use. This is because nest sites need to meet very specific conditions to be successful—and the turtles know that their birthplace meets those conditions.
(Shortform note: A 2023 study demonstrated that magnetoreception is likely more common in animals than once thought. Scientists discovered that a molecule present in all living cells can make animals sensitive to magnetic fields—if there’s enough of it. Their research suggests that many animals in addition to those we already know about have magnetoreception. Earlier research into animal behavior found that even dogs seem to have magnetoreception, which they can use instead of or in addition to smell for navigation. They employ odd methods of doing this: Many dogs align themselves along a north-south axis when defecating, which scientists believe may help them map their location relative to other spots, such as their starting point.)
