Ants build higher nests when there are no visible landmarks

In the harsh saltpans of North Africa, a unique breed of ants displays remarkable navigational prowess. These desert ants, known as Cataglyphis fortis, traverse vast expanses of desert to gather food for their colonies, journeying far from their nests into this barren and hostile terrain. 

The real challenge, however, begins once the ants find food – typically a deceased insect – and must promptly navigate back to their nest through the extremely hot and desolate environment.

Marilia Freire, the lead author of a recent study published in Current Biology, spoke about the impressive orientation abilities of these insects. “The desert ant Cataglyphis fortis stands out due to its exceptional ability to navigate and forage in the harshest environments,” she said. 

Ants have a fascinating internal navigation system

According to Freire, these ants employ an innate navigation mechanism known as path integration, using a sun compass and step counter to track their covered distances. The ants also use both visible and olfactory cues, an ability likely refined through evolution in their arduous habitat, resulting in a navigation system unparalleled in precision.

The research team, observing these ants in Tunisia, noted an intriguing aspect of their nest structures. The nests situated in the center of the saltpans, where landmarks are sparse, had high mounds at their entrances. 

Conversely, nests closer to the shrub-laden edges of the saltpans boasted less pronounced or barely discernible hills. This led the researchers to question if these distinct differences were aiding the ants in homing back to their nests.

How the study was conducted

Markus Knaden of the Max Plank Institute for Chemical Ecology described the goal of the study: “It’s always challenging to determine if an animal’s behavior is purposeful or coincidental. The high nest mounds in the saltpan’s center could be an outcome of varying soil structures or wind conditions. For our study, we devised a plan to remove these mounds. We then provided some nests with artificial landmarks and left others without, closely observing the resultant behavior.”

The researchers tracked the ants’ movements using a GPS device. This method allowed for detailed monitoring of the ants’ paths to the saltpans and their journeys back home. 

What the researchers learned

Freire revealed a surprising discovery: “We noted that desert ants can travel much farther distances than we previously thought, with the longest single distance being over two kilometers. However, we also found a high mortality rate, with around 20% of foraging ants failing to return home after long journeys, succumbing to the harsh conditions. This phenomenon underscores the extreme selective pressure for superior orientation.”

Further experiments indicated the vital role of nest hills as visual cues. The researchers painted a grid on the floor, which helped track the ants’ movements accurately during their final approach to the nest. 

When the nest hills were removed, fewer ants were able to find their way back. Simultaneously, their colony members began rebuilding nest mounds as quickly as possible. 

Interestingly, when artificial landmarks – small black cylinders – were placed near the nest entrances from which the researchers had removed mounds, the ants did not invest in constructing new ones, suggesting the cylinders were adequate for orientation.

Many questions left unanswered

In ant colonies, work is divided among the members. Older and more experienced ants typically undertake foraging, while younger ants are tasked with building. 

Thus, there must be some communication flow between these groups, though the researchers are still unclear about how this is accomplished. Freire speculated that ants inside the nest might notice fewer foragers returning home, prompting an increase in hill-building activities at the nest entrance.

Markus Knaden, who has been studying desert ants for a quarter of a century, continues to be captivated by their extraordinary capabilities. “These ants, despite their small brains, can learn visual and olfactory cues.”

More about ants 

Ants are an integral part of the insect family Formicidae and belong to the order Hymenoptera, which also includes bees and wasps. They are known for their complex social structures and exceptional survival skills. Ant colonies can be found almost everywhere, except Antarctica and a few islands.

Ants come in a wide range of sizes and colors, from as small as 0.03 inches to as large as 2 inches in length. Their colonies are organized with various roles including the queen, workers, soldiers, and in some species, drones. Each caste has a specific duty within the colony.

Ants have a caste system

The queen is the primary reproducing female, usually the largest in the colony, responsible for laying all of the eggs. Some colonies have multiple queens. 

The workers, which are typically sterile females, perform tasks like food gathering, nest maintenance, and brood care. 

The soldiers are larger workers who defend the colony. Drones are the male ants, whose primary purpose is to mate with the queen.

Communication and diet

Ants have a unique form of communication involving pheromones. These chemical signals allow them to leave trails that other ants can follow, alert colony members to danger, and even guide them to food sources.

Their diet varies widely and can include seeds, nectar, fungus, or even other insects and small animals. Some species, like leafcutter ants, farm their own food. They cut pieces of leaves and carry them back to their colony to cultivate a special type of fungus that they eat.

Extraordinary strength

One fascinating aspect of ants is their strength. They can carry objects 50 times their own body weight. This is due to their small size, which allows them to produce more force relative to their body weight.

Impressive construction ability

Ants are also known for their complex mound-building behaviors, creating intricate underground tunnel systems. Some species, like the red harvester ant, build their nests in a way that helps regulate temperature, humidity, and gas exchange.

Important role in Earth’s ecosystems

The study of ants, known as myrmecology, has provided important insights into topics like social organization, navigation, and symbiosis. Ants often form symbiotic relationships with other insects, plants, and even fungi. Their success as a species is often attributed to their social structure, adaptability, and ability to modify habitats.

Despite being small, ants play a crucial role in the environment. They turn and aerate the soil, allowing water and oxygen to reach plant roots. They also help control pests by preying on eggs, larvae, and adults of various pest species.

There are more than 12,000 described species of ants. However, scientists believe there are many more still undiscovered, particularly in tropical areas. Ants have survived on Earth for over 100 million years, which speaks volumes about their adaptability and resilience.

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