The Insane Biology of: Ant Colonies

Here’s a sanitized version of the provided YouTube transcript:

—

When you think of the most dominant creatures on Earth, what comes to mind? If considering sheer size, perhaps you immediately thought of the ocean and the largest animal that has ever lived, the blue whale. Or maybe, thinking of strength and ferocity, you imagined lush forests full of powerful big cats. Or perhaps, quite sensibly, you thought of us—human beings—the most intelligent and one of the most widespread creatures on the planet.

However, if you were to walk down the sidewalk or lean against a tree, the first animal you would likely encounter is something small—ants. Their total population is around ten thousand trillion, and when combined, their total weight would be about the same as that of all human beings. In terms of biomass and impact on ecosystems, these small animals are arguably the most successful creatures to have ever lived.

Ants have colonized almost every landmass on Earth. Their presence is so significant that they have influenced the evolution of countless other plant and animal species. Aggressive and warlike, yet also cooperative and altruistic, ants living in colonies exhibit some of the most complex behaviors of all insects. The colony is the central focus of their lives, and their loyalty to it is absolute. In their service to the colony, they display some of the most intricate social behaviors in the animal kingdom, leading to their nearly complete ecological dominance.

How do ant societies function, and what is it about the colony that has made ants so successful? Is it simply “strength in numbers,” or is there something more profound at play?

Even though insects were among the first animals to colonize land, cooperative insect societies are a relatively recent development. The first insects emerged around 400 million years ago, but ants didn’t appear until much later, around 100 million years ago. They coexisted with the dinosaurs, and for a long time, did not dominate the landscape. This was the era of giant dragonflies, cockroaches, and termites. It wasn’t until 60 million years ago that ants became the dominant insects, and since then, they have truly flourished. Today, there are around 16,000 different species of ants, and they are found on every continent except Antarctica.

The competitive edge that allowed ants to become a world-dominant group is their highly developed colonial existence and specialized social structure. Ant societies are divided into two castes: a non-reproductive worker caste and a reproductive royal caste. The queen is the only reproducing female in the entire colony, and the colony exists to serve her. The birth of a colony begins with the emergence of a queen.

The life of a queen begins when her mother lays a special kind of egg, different from the millions of regular worker eggs the queen will lay in her lifetime. These special eggs are laid when the colony reaches a certain size, and when they hatch, they produce ants that are larger than regular workers and have wings. These are the reproductive males and young queens.

During what is called a nuptial flight, these winged ants take to the air and mate with each other. After mating, the males die, and the females drop to the ground, remove their wings, and begin searching for a place to dig their nest. Few succeed in this journey, as predators catch most young queens before they can establish themselves. Only about 1 in 500 new queens has a chance at success. Those that do succeed become the sole egg-laying queen of their new colony.

Over her lifetime, a queen ant can lay up to 300 million eggs, depending on the species. The vast majority of these eggs hatch into dedicated worker ants—female ants whose lives are devoted to the queen’s welfare and reproductive activity. At any given time, there are millions of worker ants maintaining the colony. There can be many different types and sizes of workers even within a single colony. Some care for larvae, others excavate tunnels, some build intricate structures, while others leave the nest to search for food or engage in conflicts with neighboring colonies.

Surprisingly, it is the ant workers themselves who ultimately decide the fate of the young, choosing which worker caste they will develop into. Larvae develop into different types of workers based largely on the nutrition they receive. Those fed more insects than seeds are more likely to become larger individuals. For leafcutter ants, the variation among the workers is extreme. The largest workers, called soldiers, defend the colony, while medium-sized workers collect leaves, excavate tunnels, or manage waste, and the smallest workers care for the young and cultivate fungus—the only food source for the entire colony.

The workers operate in a flawless synchrony—a flow that may appear chaotic to us but is based on a complex system of communication, a chemical and physical language that binds these societies together. For years, scientists understood that ants must have some way to communicate in order to organize their intricate societies. However, ants have poor vision and hearing, leading scientists to believe that ant communication must work in a fundamentally different way than ours.

In 1962, leading entomologist E.O. Wilson began to unravel the mystery of ant communication. He started with the question of how ants inform other members of the colony about the location of a new food source. He noticed that ants often tap their abdomen to the ground while traveling, leading him to wonder if they were leaving some sort of chemical trail.

He began painstakingly dissecting fire ant abdomens, crushing each of the organs with an applicator stick. He would then spread the ant juice on a piece of paper in front of other fire ants to observe their reactions. As he worked through each known organ, the ants showed no interest. However, he eventually discovered an organ that had never been studied before—Dufour’s gland. When he crushed this gland and spread it across the paper, the ants responded immediately, following the trail with enthusiasm.

Over time, scientists have identified over 20 different pheromones that ants use to communicate. By combining different signals, ants have created a complex pheromonal language. African weaver ants, in particular, have the most sophisticated pheromone communication system ever studied in animals. Some of their messages are conveyed by spreading pheromones on the ground, combined with physical gestures.

When a worker wants to say “follow me, I have found food,” she deposits a trail from her rectal gland while running back to the nest. When she encounters other workers, she waves her head and touches them with her antennae. If a worker wishes to raise the alarm about an enemy, she lays short looping trails around the intruder using secretions from her sternal gland.

Other signals are sent through the air. When an African weaver ant worker encounters an enemy in her territory, she releases a mixture of four chemicals that convey a message and elicit a response from other workers nearby. The first signal tells the other ants to “be alert.” The next instructs them to search for the trouble. The third tells them to come closer and bite anything in their path, and the final compound urges them to attack.

Scientists believe that the combination of these signals closely resembles syntax found in human language. A main reason ants are so successful in the world is the same reason that humans are: communication gives ants the remarkable ability to cooperate.

Among all ants, weaver ants are particularly impressive. They dominate the forests in Africa and Australia, largely due to their complex and efficient chemical communication. However, perhaps more remarkable than their ability to communicate effectively is what they can achieve with it. Weaver ants do not live in or on the ground but in trees. To keep their large populations safe, they construct their own housing. They weave branches and leaves together to create an architectural feat, complete with a network of different rooms, roofs, walls, and floors.

To begin the process, a single ant searches for a suitable, flexible leaf. It tests the edges to see if the leaf will curl. If successful, other ants are attracted to the task and begin pulling the edge as well. As the leaf bends more, more workers arrive, lining up in precise rows to grip the edge and pull it toward another leaf. If the gap is too large for a single row of ants to seal, they perform an impressive acrobatic tactic: they chain their bodies together to form a bridge. Workers climb down the bodies of others until the chain can reach the other leaf edge, sometimes extending up to 10 workers long. Once the leaf edges are within reach, the workers move into position to seal the leaves together. What appears to be glue on the finished structure is something more surprising.

Once the bent leaves are ready to be sealed, the workers collect larvae in their final stages of development and use their silk threads to bind the leaves together. Holding the larvae in their mandibles, the workers move them back and forth across the leaf edges, using their silk like a glue gun. The larvae respond to this motion by exuding thousands of threads of silk, which become a sheet between the edges and serve as a powerful adhesive.

Structures like this demonstrate ants’ capacity to organize their labor effectively, with millions of individuals combining their abilities into something much greater. It’s easy to assume that their effectiveness comes down to strength in numbers, along with the communication to orchestrate the work. However, this does not account for all of their behavior and success. There is something more unifying in the world of ants. The cooperation among individual ants is so profound that it prompts scientists to rethink the concept of individuality.

The power of a group is evident—more ants working together can find food more quickly, build more impressive structures, and defend against enemies more effectively. While working together is common in nature—such as birds in flocks or bison in herds—individuals in these groups still look out for their personal interests.

This is not the case for ants. Worker ants typically die young and do not create offspring. Their existence is sacrificial, and they exhibit no self-interest. Certain ants have been found to suffer a death rate of 6% per hour when outside the nest due to conflicts with neighboring colonies. On average, each forager survives for only a week, but during that time, she manages to collect 20 times her own body weight in food for the colony—all to support the group and ultimately, the queen.

This unwavering loyalty to the queen and the self-sacrifice for her cause becomes even more evident when a queen dies. Logic would suggest that when the queen dies, the workers would raise another queen to replace her. However, in most cases, the colony fails to produce a royal successor and declines until the last worker dies. They simply do nothing until there is no one left.

This level of altruism and self-sacrifice is so rare in the animal kingdom that it has led scientists to reconsider what it means to be an individual. If ant individuals in a colony are not competing against each other, if they are tightly bound by communication and a caste division of labor, and if they cannot survive outside the colony for very long, does the concept of the individual break down?

The idea of the superorganism has been debated for decades. With ants, it suggests that the colony is the organism, where the queen is the reproductive organ and the workers serve as the supporting brain, heart, and gut. The exchange of food among the workers is akin to the circulation of blood. The most advanced ant societies, like weaver ants, driver ants, or leafcutter ants, fall into this category, where their workers do not compete among themselves and do not reproduce outside of the royal caste.

This capacity for the colony to function as a single superorganism has prompted scientists to reconsider evolutionary theory as a whole. In the 1960s and 70s, the conventional view of evolution centered around genes alone. Popularized by Richard Dawkins’ book “The Selfish Gene,” this perspective suggested that the more two individuals are genetically related, the more sense it makes for them to behave selflessly toward each other—that all altruistic group behavior stems from each individual’s competitive desire to enhance the survival of their kin.

However, some ant biologists, like E.O. Wilson, believed that this could not be the entire story. Instincts from social species like ants extend far beyond the urge to protect their immediate kin. The group must also play a role in evolution, regardless of whether group members are related. This idea gave rise to the theory of multi-level evolution, or group selection, where natural selection acts at the level of the group rather than the individual.

The way ant societies function, both in their daily lives and within the context of evolution, has fascinated humans for decades. They have sparked heated debates among the world’s top scientists and captured the curiosity of children everywhere. Their world operates in ways our brains can barely comprehend—with chemical signals painted on the ground and instincts that drive them to perilous endeavors. Yet, their sociality, cooperation, and complexity mirror our own in many ways. Studying ants will continue to reveal insights about the nature of evolution and, in turn, provide answers about our own society and individuality.

Exploring the animal kingdom offers insights into our world and leads researchers on various journeys—both intellectual and physical. Some research on ants occurs in the field, in the steamy tropics or the frigid regions of northern Finland, while other studies are conducted in labs with complex apparatuses designed to investigate ant chemical trails or their tendencies to engage in conflict. Learning about the efforts required to conduct such research is often just as intriguing as the science itself.

This is why we decided to start a podcast. “Modulus,” hosted by me and Brian from Real Engineering, is a podcast about the people behind the science we explore here on YouTube. We talk to scientists who are at the forefront of research and to those affected by the topics we discuss.

The second episode of “Modulus” is out now. In this episode, I speak with two pioneers of the ocean—some of the world’s first saturation divers. They share their experiences living at the bottom of the ocean and how it affects both the body and mind. Their personal accounts of the immense pressure on their bodies highlight that deep-sea diving is not for the faint of heart.

This episode is available now on Nebula, the streaming platform created by me and several other educational YouTube content creators. It’s the place to watch and listen to our videos and podcasts ad-free, along with original content that is not available anywhere else, such as Real Engineering’s “The Logistics of D-Day” or Sam from Wendover’s new trivia show, featuring creators like Brian competing in fun challenges.

We can take more risks and have more fun on Nebula, where we don’t have to worry about the YouTube algorithm. There is a wealth of original content available, with more being added all the time.

To make it even better, Nebula has partnered with CuriosityStream, the streaming platform with thousands of high-quality documentaries. There are many excellent nature films, including David Attenborough’s “Ant Mountain,” which explores one of the largest animal societies in the world—a supercolony of ants with more than a billion members nestled within the Swiss Alps. It delves into a whole new area of ant biology that I never knew existed, and since it’s a David Attenborough film, you know it’s going to be exceptional.

For a limited time, CuriosityStream is offering 26% off their annual plans, making a yearly subscription just $14.79. By signing up at curiositystream.com/realscience, you will receive a subscription to CuriosityStream and Nebula for just $14.79 for the entire year. Signing up is also the best way to support this channel and all of your favorite educational content creators.

Thank you for watching! If you would like to see more from me, the links to my Instagram, Twitter, and Patreon are below.

—

This version maintains the content’s integrity while removing any potentially sensitive or inappropriate language.