Ants

The comings and goings of ants: how are social skills shaped in an ever-changing world?

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A colourful study of the natural history of ants that takes in dry deserts and lush forests aims to show that sociality is shaped by, and changes with, the environment

Ant bridge (ants crossing to other side in harmony).
Ants, like many other animals, work together for the survival of the group.

The Ecology of Collective Behavior Deborah M. Gordon Princeton Univ. Press(2023)

Collective behaviours are present throughout nature — from groups of genes being activated simultaneously to shoals of fish swimming in unison for protection against predators and mounds of insects working together to build nests. But biologist Deborah Gordon worries that the evolutionary biologists who study how these phenomena evolved are missing a trick, because they often don’t consider that the ever-changing environments in which animals live are fundamental to shaping such behaviours. In The Ecology of Collective Behavior, she tries to set the record straight.

Gordon has spent decades studying the natural history of two ant species that live in very different environments, paying acute attention to how the insects’ stirring, dynamic habitats shape their behaviour. These observations form the bedrock of her book.Survival of the nicest: have we got evolution the wrong way round?

First, she describes the red harvester ant Pogonomyrmex barbatus, which lives in the harsh, parched deserts of New Mexico. Affectionately known as pogos, these ants are deep red and around 10 millimetres long — an impressive size for an ant. They live in colonies, which contain more than 10,000 female workers, and rely on seeds scattered on the desert floor for both food and water. Seed sources change slowly throughout the year as plants wax and wane; there is mostly a plentiful and constant supply of food. But collecting seeds is hazardous. Deserts are dry, so pogos live in a catch-22 world: they must risk desiccation to gather the water they need.

Gordon shows that this delicate trade-off is achieved by a slow but robust mechanism through which foragers recruit nestmates in the search for food. When a female returns to the nest with her bounty, she releases hydrocarbons from her outer cuticle to indicate to her sisters that there’s food out in the desert.

A fleeting touch from a forager’s antennae sends others scuttling out of the nest. They head out in random directions, but that’s OK, because the seeds are spread out on the desert floor, not clustered in patches. Plentiful food and favourable environmental conditions — days that are not too hot, for instance — mean that many foragers return to the colony and recruit many others. Conversely, under bleaker circumstances, fewer ants return to muster recruits. In this way, simple positive feedback regulates the steady collective behaviour of thousands of ants.Bumblebees show uniquely human behaviour

Next, Gordon turns to the arboreal turtle ant, Cephalotes goniodontus, which forages in the canopies of Mexico’s dry tropical forests. Unlike the desert harvesters, turtle ants spread their brood across many nests perched in the canopy, connected by a complex net of tangling vines, shifting leaves and moving stems. Their food sources are ephemeral — foragers must exploit bursts of nectar from transient floral blooms.

Each foraging turtle ant lays a trail of pheromones wherever she goes — independent of whether she has discovered a food source or not — while following the trails laid by others. These trails constantly bifurcate, and paths can change on an hourly basis. Which route should each forager follow?

The answer is simple, Gordon reveals. The ants follow the smelliest path — the one with the strongest pheromone signal — and keep reinforcing profitable trails until something tells them to stop, such as the presence of a predator or a broken branch. This ensures that the ants can find the most lucrative foraging spot and rapidly adjust the information flow if needed, changing their behaviour in a constantly changing environment.

Red Harvester Ant workers clear particles of sand from the entrance to their nest.
Red harvester ants clean their nest together.Credit: Clarence Holmes

Unpredictable environments

Pogos and turtle ants solve similar problems in distinct ways. How they do it is dictated by their environment. Gordon borrows concepts from network science to describe how turtle ants function in modules — units in which most information flow occurs — to keep communication local, enabling them to respond rapidly to the ever-changing availability of resources. By contrast, the centralized regulation of pogos is the epitome of low modularity: the nest is the sole source of communication.

Gordon argues that the nature of the environment and the resources it provides determine the types of collective-foraging mechanism that evolve — not just for ants, but for all social organisms. The extent to which ecology drives the evolution of social behaviour in this way has been overlooked, she suggests.How STRANGE are your study animals?

I agree that researchers need to better recognize that organisms exist, and have evolved, in a dynamic, often unpredictably messy world, and to acknowledge that this influences their behaviour. I admire how the author takes inspiration not only from careful field experiments — removing ants or changing the amount of available resources and observing how the insects respond — but also from the classical science of natural history. Many evolutionary biologists could learn a lot by rediscovering this way of working.

But I am less convinced by Gordon’s suggestion that her ideas are at odds with the ‘prevailing theory’ for social behaviour. Inclusive fitness theory — an idea put forward by UK evolutionary biologist William Hamilton in 1964, and accepted widely in the field — suggests that social behaviours evolve when the benefits of cooperating with relatives exceed the costs (W. D. Hamilton J. Theor. Biol. 7, 1–16; 1964). Hamilton’s ideas stemmed from his observations of wasps, ants, bees and birds in their natural habitats, and are supported by strong experimental and theoretical evidence.

Hamilton’s theory suggests that cooperation will prevail in unpredictable environments, with some animals choosing to help raise their relatives’ young rather than having their own (P. Kennedy et al. Nature 555, 359–362; 2018). This phenomenon is seen often in the natural world, from slime moulds to termites. Thus, the idea that dynamic environments help to shape social behaviour is already part of the accepted theory of social evolution.

I think the confusion arises because Gordon conflates proximate (mechanistic) and ultimate (evolutionary) processes. Her book offers useful insights into the proximate processes that regulate collective behaviour on a day-to-day basis, and the role of the environment in shaping and maintaining such behaviours. I agree that the interactions between organisms and their environments have become increasingly overlooked because fewer researchers are studying animals in their natural environments. But these insights are not at odds with the prevailing theory of how collective behaviours evolve.

In her final chapter, Gordon remarks: “The whole appears to be more than the sum of the parts, because the parts do not sum — they intertwine, jostle, and respond.” This heartening statement is a great description of the ecological and evolutionary complexities that shape our world. It’s these complexities that all biologists should keep in mind.

Source: Nature

Scientists finally discovered how ants took over nearly the entire planet

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The world is teeming with an estimated 14,000 species of ants that, taken together, number in the quadrillions! These ubiquitous insects have spread across all continents except for the frozen expanse of Antarctica, marking an incredible evolutionary success story. 

But how did they manage to establish such a significant presence on our planet? 

A team of researchers went to the bottem of this and published their findings in the peer-reveiwed scientific journal Evolution Letters. In this article we will discuss their intruiging findings

The team, led by Matthew Nelsen, a research scientist at the Field Museum in Chicago, combined fossil records, DNA data, and modern species’ habitat preferences to retrace the ants’ journey. They painstakingly collected and studied climate data of 1,400 modern ant species and then contrasted this with a time-scaled reconstruction of the ant family tree derived from genetic information and fossilized amber-encased ants.

UNRAVELING THE ANT-PLANT SYMBIOSIS THROUGH EVOLUTION

In their research, the scientists discovered that ants’ evolutionary path was intertwined with that of flowering plants. Approximately 140 million years ago, ants and flowering plants – or angiosperms – originated and gradually spread from forests to other habitats. This simultaneous spread wasn’t a mere coincidence; in fact, the ants were closely following the flowering plants’ lead.

Exploring this further, the team found that around 60 million years ago, ants primarily resided in forested areas, building their nests underground. However, as some forest-dwelling plants evolved to release more water vapour through their leaves, creating rainforest-like conditions, ants began to ascend. 

Alongside ants, other creatures like frogs and snakes also transitioned to this new, wetter environment. They weren’t just adapting to a new climatic condition – they were forming a brand new, vibrant ecosystem up in the trees!

The scientists also discovered that as flowering plants began to adapt to drier, more arid regions outside of the forest, ants took this as a cue to move as well. Plants seem to have incentivized this migration by evolving specific features to feed ants, such as fleshy appendages on seeds called elaiosomes. As ants harvested these elaiosomes, they inadvertently aided in the dispersal of plant seeds, creating a mutual benefit for both species.

THE FAR-REACHING IMPACT OF PLANT COMMUNITIES ON BIODIVERSITY

The research provides more than just fascinating insights into the ants’ evolutionary journey. It underlines the profound and cascading impact that shifts in plant communities – due to historical and modern climate change – can have on other dependent organisms, including ants. As Nelsen points out, this research reinforces the idea that plants play a critical role in shaping ecosystems, and any alterations to their communities can have significant ripple effects on the biodiversity and the structure of ecosystems.

Plants have been the silent architects of the world, influencing the ecology and evolution of numerous organisms, including ants. This study has underscored that, providing another compelling example of the powerful interplay between different life forms on our planet. Our ant allies and their blossoming companions indeed share a deep-seated relationship, having jointly navigated the path of evolution for over a hundred million years. It’s a testament to the intricacy of life and its remarkable adaptability, reminding us of the delicate balance that exists in nature.

Even Ants Use Natural Medicine Because IT WORKS

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Even Ants Use Natural Medicine Because IT WORKS

From humans to insects, using natural substances to treat infection is a concept as old as time itself.

A fascinating article published on TechTimes online titled, “Ants Treat Their Own Fungal Infections With Natural Medicine,” illustrates how universal the use of natural substances to maintain health is across the animal kingdom.

Researchers discovered that ants infected with a deadly fungus will ingest a naturally occurring — albeit pro-oxidative — molecule known as hydrogen peroxide when offered in combination with honey, presumably in order to medicate themselves:

Scientists studying an ant species called Formica fusca offered the insects a choice between a pure honey solution and a honey solution spiked with toxic hydrogen peroxide. They found that ants afflicted by a fungal infection tended to opt for the hydrogen peroxide solution, whereas healthy ants were more likely to avoid it. This shift in preference suggests that the ants recognize that hydrogen peroxide helps fight off fungal infections and that its noxious effects become worth the risk when an ant falls ill.”

Furthermore, the infected ants who consumed hydrogen peroxide spiked honey had a significantly lower mortality rate (45%) versus the ants who consumed pure honey (65%). On the other hand, healthy ants fed pure hydrogen peroxide saw a 20% mortality rate, revealing that out of the context of infection where hydrogen peroxide is beneficial unnecessary “treatment” can have adverse health effects.

The researchers also noted that the ants were capable of properly dosing themselves:

When offered a solution that had only a low concentration of hydrogen peroxide, infected ants typically chose to eat equal amounts of the toxic food and the pure food. Offering a stronger hydrogen peroxide solution caused the infected ants to change the balance, eating only half as much of the toxic solution as they did of the pure solution.”

It should also be noted that all honey naturally contains hydrogen peroxide, which is known to contribute to its antimicrobial properties.

Is Hydrogen Peroxide A “Natural Remedy”?

The discovery that ants are capable of using hydrogen peroxide as a “natural medicine” is especially interesting considering that it is one of the most popular over-the-counter remedies for topical infection that humans have ever devised. As you know, it usually comes in a brown bottle at the pharmacy or grocery store and millions of bottles are sold throughout the world.

But hydrogen peroxide isn’t just a natural antiseptic. It is also believed to have a therapeutic role internally. This is accomplished both through direct ingestion (note: extreme caution should be exercised when using it this way), and by being formed as a natural metabolic byproduct of high-dose vitamin C therapy. Indeed, hydrogen peroxide produced via vitamin C treatment or administered directly has been studied as a potential natural alternative for conditions as serious as cancer.[1] [2]  [3]  [4]

Advocates of using hydrogen peroxide internally believe it is safe because our body produces it naturally in immune cells known as phagocytes that engulf pathogens. An important differential consideration, however, is that immune cells are able to produce and utilize very small and specific amounts at the very time and place they are needed — which reduces collateral damage. One cannot expect that orally ingesting hydrogen peroxide would necessarily have the specificity needed to ensure the highly reactive molecules do not damage non-target host tissues.  Nonetheless, there are a wide range of advocates for this approach who may find their claims vindicated a little more knowing that even sick ants have been shown to ingest the stuff with significant benefit.

Regardless of these controversies, the point is that hydrogen peroxide is a relatively natural means to fight infection, and it is a remarkable fact that even ants have evolved to be able to recognize its value and use it in a very specific way that appears very much like self-medication. I don’t think anyone is going to accuse ants of practicing “woo” when the outcome of their “quackery” is decreased mortality. I should only hope that in the future we may all apply the same results-based evidentiary standard to the thousands of natural therapies out there that are at least as effective as conventional treatments, and are almost always safer and more affordable. If it works it works. And for those needing scientific “evidence” in addition to the evidence of experience or timeless folkloric traditions, check out our extensive research database that covers over 3,000 ailments.

References

[1] Qi Chen, Michael Graham Espey, Murali C Krishna, James B Mitchell, Christopher P Corpe, Garry R Buettner, Emily Shacter, Mark Levine. Pharmacologic ascorbic acid concentrations selectively kill cancer cells: action as a pro-drug to deliver hydrogen peroxide to tissues.Proc Natl Acad Sci U S A. 2005 Sep 20;102(38):13604-9. Epub 2005 Sep 12. PMID: 16157892

[2] Qiu-Sheng Zheng, Xi-Ling Sun, Chang-Hai Wang. Redifferentiation of human gastric cancer cells induced by ascorbic acid and sodium selenite. Biomed Environ Sci. 2002 Sep;15(3):223-32. PMID: 12500663

[3] Roberto Davicino, María G Manuele, Graciela Ferraro, Blas Micalizzi, Claudia Anesini. Modulatory effect of hydrogen peroxide on tumoral lymphocytes proliferation. Immunopharmacol Immunotoxicol. 2009;31(1):130-9. PMID: 19951073

[4] Youn Wook Chung, Dae-won Jeong, Joo Yun Won, Eui-Ju Choi, Yung Hyun Choi, Ick Young Kim.H(2)O(2)-induced AP-1 activation and its effect on p21(WAF1/CIP1)-mediated G2/M arrest in a p53-deficient human lung cancer cell. Carcinogenesis. 1998 Aug;19(8):1357-60.PMID: 12054510

Ants respond as a collective “superorganism” when they sense a predator

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A swarm of ants scurrying over the ground may look like a relatively chaotic scene, but don’t underestimate these very complex and social insects.

A new study by researchers in the UK has found that highly cooperative ants are capable of coordinating together to form a single entity – effectively uniting as one to become a “superorganism” when faced by a predator or threat.

“Ants react very differently, and in a coordinated fashion, to perceived predator attacks depending on their location,” said Thomas O’Shea-Wheller from the University of Bristol. “Just as we may respond to cell damage via pain, ant colonies respond to the loss of individuals via group awareness and reaction.’’

To measure how this behaviour is demonstrated, the researchers simulated a range of different predator attacks on 30 migrating ant colonies. In each simulation, using almost military-sounding tactics, they picked off ant scouts at the colony’s periphery, before separately removing worker ants toiling in the middle of the nest.

The colony was not amused. When the collective body of insects became aware that its scouting parties had been taken out, it withdrew its extended, foraging ‘arms’ that drew out from the centre and reassembled into a tight, defensive formation.

But once worker ants were then removed from the centre of the nest, the opposite effect happened. Sensing a new threat at the very heart of the colony, the ants scattered outward to find a safer location.

The researchers suggest that these findings, which are published in PLOS ONE, draw parallels with the nervous response systems of single organisms. They liken the colony’s arms withdrawing to when you burn your hand on a stove and quickly yank it back, whereas the outward exodus from a central threat is what people might do if their house was on fire (not that any singular organisms can pull this particular trick off, scattering in all directions at once).

“Our findings lend support to the superorganism concept, as the whole society reacts much like a single organism would in response to attacks on different parts of its body,” the researchers write. “The implication of this is that a collective reaction to the location of worker loss within insect colonies is key to avoiding further harm, much in the same way that the nervous systems of individuals facilitate the avoidance of localised damage.”

Ants in space grapple with zero-g

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ants on the ISS
On board the ISS the ants were kept inside special plastic containers, with vents to allow them to breathe

Ants carried to the International Space Station were still able to use teamwork to search new areas, despite falling off the walls of their containers for up to eight seconds at a time.

Their “collective search” was hampered but still took place, biologists said.

The insects also showed an impressive knack for regaining their footing after taking a zero-g tumble.

Researchers want to learn from the ants’ cooperative methods and develop search algorithms for groups of robots

The ants were sent aloft in a supply rocket in January 2014, and results from the experiments are published in the journal Frontiers in Ecology and Evolution.

The team is now beginning a citizen science project where schoolchildren can help collect data from other ant species – in their classrooms, rather than up in space.

Speaking to the BBC’s Science in Action, senior author Deborah Gordon said that ants have demonstrated their remarkable collective abilities in myriad environments on Earth, but the results from the microgravity conditions of the ISS were something new.

“We had no idea what the ants would do. We didn’t know if they would be able to search at all,” said Prof Gordon, a biologist at Stanford University.

As it turned out, although they had a little difficulty maintaining contact as they crawled, once adrift the ants showed a “remarkable ability” to get their six feet back on solid ground.

“Sometimes they would grab onto another ant and climb back down… And sometimes, they somehow managed to just flatten themselves back onto the surface. I think the biomechanics of that are interesting,” Prof Gordon said.

Testing times

The team sent up eight colonies of 80 common pavement ants, housed in small, transparent plastic boxes. Each container had a “nest” area where the animals lived.

To start the experiment, a barrier was removed that allowed them to explore a new area. After a few minutes, a second barrier was lifted, expanding the available territory even further.

“The idea is to ask the ants to search a small space – and then provide more space and see what will happen when the same number of ants have to use a larger space,” Prof Gordon explained.

Equivalent experiments were also run back on Earth, for comparison.

Down on ground level, adding extra space and dropping the “density” of ants caused them to adjust their paths, covering more ground and spreading out much more. In this way, nearly every corner of the container was visited by more than one ant within five minutes.

The ants in space still did their best to search, moving out into the expanded area as expected – but they were nowhere near as effective as their counterparts on the ground, which had the luxury of normal gravity.

experiment apparatus on the ISS
astronaut observing the experiment
The experiments were overseen by Nasa astronauts on the ISS and recorded by cameras

Battling to keep their feet on the plastic surfaces, the space-ants tended not to spread out as effectively. And some parts of the new area never even encountered the patter of six tiny feet.

“The ants didn’t do as well as they might have in microgravity,” Prof Gordon said. “I think that’s partly because the effort to hold on led to them moving more slowly, and so they didn’t have a chance to cover the ground as thoroughly.”

Adding to the problem was the fact that ants kept dropping off the surfaces altogether, tumbling in the air for periods lasting three to eight seconds. So the ants were constantly interrupted in gauging how far apart they were.

“I don’t think it’d be that easy to use interactions to keep track of density, because about 10% of the ants at any time were just floating around – and so they were not really available to interact.”

Call for help

When the history-making ants took their first steps in zero-g they were adding one more new environment to an already extensive list. It just happens to be a very new environment.

“There’s not been a lot of evolution to shape their collective search in microgravity,” Prof Gordon said.

By contrast, nearly every clime on Earth is inhabited by at least one of the 14,000 species of ant.

Different strategies have evolved in different places – for example, the European pavement ants that were taken into space tend to head straight for the edges of their new territory, while a species of Argentine ants, which the team studied previously, tends to work over fresh ground slowly and thoroughly, inch by inch.

ant experiment set-up
The researchers have provided instructions for school classes to test more ant species, here on Earth

“All ants have to perform collective search and we don’t know how they do it. There may be very interesting algorithms for collective search that we haven’t discovered,” Prof Gordon said.

Algorithms like these could help program robots to search in groups, without the need for a central control centre. And Prof Gordon is asking for help to find out more about them.

She and her team have set up a website with instructions for school classes to run the same experiment, using equipment they can make themselves, on whatever species of ant are local to their area.

“We hope that kids around the world will try this same experiment with all of the many thousands of species of ants that have never been studied,” Prof Gordon said.

She has set up a website for sharing the results and hopes to build up a database of “how different species solve this problem differently” around the world.

There is no suggestion, yet, that any other species will get the chance to strut its stuff in space.