Rise of the Planet of the Ants

These days, we’ve been hearing quite a bit about a future in which humans find their dominion over the planet suddenly challenged by a group of super intelligent apes. This may make for an exciting Hollywood movie plot and some stunning visual effects, but I wonder whether we really need to look to humanoid science fiction in order to feel a shiver of doubt regarding our supremacy as a species.

Maybe all we need to do is to look at the world the way it is, a world that could well be called … The Planet of the Ants!

So, why is it that we should feel just a wee bit threatened by these small six-legged colonizers? Here are just a few reasons.

Quadrillions of Ants

Burning Man seems more crowded every year, doesn't it? (photo credit: Mehmet Karatay)

Like us, ants thrive just about anywhere, with the exception of Antarctica and a few isolated islands. Moreover, while there are approximately seven billion of us on the planet, conservative estimates put the number of ants at between one and ten quadrillion.1 That’s between 150,000 and 1,500,000 ants for each and every one of us. At the higher figure, this means that, if you were to put all the world’s ants onto a giant scale, they would weigh about as much as all of the humans on the planet put together.2 In fact, on average, it has been estimated that ants make up 15–20% of the terrestrial animal biomass on Earth (and more than 25% of the animal biomass in tropical regions).3

Our tendency as humans is to unquestioningly assume that we are far and away the most successful species that has ever been. If we take a step back, though, and simply consider the above numbers and the possibility that an animal’s success is most properly measured by the degree to which it has been able to thrive in various environments, perhaps we should already be feeling a pang of doubt about how incontestable our supremacy really is.

Ants Teach

While many animals are able to learn through imitation, ants are the only non-mammal known to engage in interactive teaching.4 In at least one species of ant, knowledgeable workers actively teach inexperienced nest mates where to find food through a process known as “tandem running,” in which the lead worker ant recruits an inexpert follower, and then makes sure that the follower stays on track, slowing down when it lags and speeding up when it gets too close.

Ants Learn

Ants are also able to engage in so-called latent learning, whereby they memorize information that they cannot use at once, but that may be useful later on – a behavior that’s been labeled as “planning.”5 Specifically, ants have been shown to be able to reconnoiter potential new living spaces, retaining information about relative desirability and tailoring their choices based on how urgently the need to move is.

Ants Can Learn to Navigate Mazes

Ants can be trained to remember multiple visual patterns presented in a fixed sequence, enabling them to navigate mazes.6 Ok, I’m not sure how exactly this leads to world domination, but it is definitely pretty cool.

Ants Practice Agriculture

Approximately 50 million years ago (and, accordingly, approximately 49+ million years before Homo Sapiens first arose as a species), ants began engaging in agriculture.7 Today, different species of leafcutter ants have adopted a purely agrarian lifestyle, feeding exclusively on gardens of fungus that they actively weed and cultivate, feed with fresh-cut leaves, and keep free from parasites and other pests.8 Here’s a video of some fungus farming ants:

Ants Engage in Animal Husbandry

Some ants raise aphids and feed on the sugary honeydew the aphids secrete when “milked” by the ants’ antennae. The ants are careful with their herds, keeping predators and parasites away, moving the aphids from one feeding location to another, and often bringing the aphids with them when they migrate.9 Here’s a video of ants tending to their aphids:

Ants Sometimes Enslave Other Ants

Certain types of ants are incorrigible slave-makers, raiding other colonies of ants and making captured slaves perform all routine tasks for their masters, including brood care, foraging, and even feeding slave-maker workers who are unable to feed themselves.10 Obviously, this isn’t a particularly attractive ant characteristic, but unfortunately it is one that may seem all too familiar to us humans.

Ants Use Tools

That’s right, tools. For example, some ants transport liquid and other non-solid food by dropping bits of leaves, sand or mud pellets or pieces of wood into a pool of food and, after the food has soaked in, using these objects to carry the meal back to their nests.11 Other ants use pebbles and soil pellets as weapons, dropping them on other ants or ground-dwelling bees, and then attacking and killing their competitors.12

Ants Build Cooperative Solutions

Hey, watch your foot! You're stepping on my head! (photo: Mlot, Tovey & Hu)

Ants, including army ants, are known to self-assemble into living bridges or ladders that allow them to cross gaps while on the move. When a single ant cannot make it across alone, other ants will successively grab on, steadily lengthening the bridge until it’s long enough to reach the destination. These structures, which can span significant distances and can even cross water, are then used by the rest of the colony and may stay in place for hours, until traffic dies down.13 Comparably, fire ants self-assemble into waterproof rafts to survive floods. These rafts can be made up from anywhere from a few hundred to many thousand ants and are incredibly durable, allowing ants to sail for months at a time as they migrate.

Ants Have “Collective Intelligence”

The concept of collective intelligence has been hot lately, with a number of books and articles describing how groups can make collectively make sophisticated decisions and solve complex problems, even where each individual in the group knows very little, collectively a g (think of the analogy of each individual acting as a neuron, and the group as a whole acting as a collective brain). Collective intelligence is a topic unto itself, one we may address in future posts, but for now suffice it to say that if ants truly can make wise decisions as a group, we humans may really have something to envy!

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ResearchBlogging.org1Holldobler, B & E. O. Wilson (2009). The Superorganism: The Beauty, Elegance, and Strangeness of Insect Societies. New York: W. W. Norton. p. 5. ISBN 0-393-06704-1.

2Ibid.

3Schultz, T. (2000). In search of ant ancestors Proceedings of the National Academy of Sciences, 97 (26), 14028-14029 DOI: 10.1073/pnas.011513798.

4Franks, N., & Richardson, T. (2006). Teaching in tandem-running ants Nature, 439 (7073), 153-153 DOI: 10.1038/439153a; Richardson, T., Sleeman, P., McNamara, J., Houston, A., & Franks, N. (2007). Teaching with Evaluation in Ants Current Biology, 17 (17), 1520-1526 DOI: 10.1016/j.cub.2007.08.032.

5Franks, N., Hooper, J., Dornhaus, A., Aukett, P., Hayward, A., & Berghoff, S. (2007). Reconnaissance and latent learning in ants Proceedings of the Royal Society B: Biological Sciences, 274 (1617), 1505-1509 DOI: 10.1098/rspb.2007.0138.

6Chameron, S., Schatz, B., Pastergue-Ruiz, I., Beugnon, G., & Collett, T. (1998). The learning of a sequence of visual patterns by the ant Cataglyphis cursor Proceedings of the Royal Society B: Biological Sciences, 265 (1412), 2309-2313 DOI: 10.1098/rspb.1998.0576; Reznikova, Z. 2008: Experimental paradigms for studying cognition and communication in ants (Hymenoptera: Formicidae). Myrmecological News 11: 201-214.

7Schultz, T., & Brady, S. (2008). From the Cover: Major evolutionary transitions in ant agriculture Proceedings of the National Academy of Sciences, 105 (14), 5435-5440 DOI: 10.1073/pnas.0711024105.

8Ibid.; Schultz, T. (1999). Ants, plants and antibiotics. Nature, 398 (6730), 747-748 DOI: 10.1038/19619.

9Nielsen, C., Agrawal, A., & Hajek, A. (2009). Ants defend aphids against lethal disease Biology Letters, 6 (2), 205-208 DOI: 10.1098/rsbl.2009.0743; Styrsky, J., & Eubanks, M. (2007). Ecological consequences of interactions between ants and honeydew-producing insects Proceedings of the Royal Society B: Biological Sciences, 274 (1607), 151-164 DOI: 10.1098/rspb.2006.3701.

10Pohl, S., & Foitzik, S. (2011). Slave-making ants prefer larger, better defended host colonies Animal Behaviour, 81 (1), 61-68 DOI: 10.1016/j.anbehav.2010.09.006; Brandt M, Foitzik S, Fischer-Blass B, & Heinze J (2005). The coevolutionary dynamics of obligate ant social parasite systems–between prudence and antagonism. Biological reviews of the Cambridge Philosophical Society, 80 (2), 251-267 PMID: 15921051; Hölldobler, B. & Wilson, E.O., 1990. The Ants, Harvard University Press.

11FELLERS, J., & FELLERS, G. (1976). Tool Use in a Social Insect and Its Implications for Competitive Interactions Science, 192 (4234), 70-72 DOI: 10.1126/science.192.4234.70.

12See, e.g., Pierce, J. (1986). A Review of Tool Use in Insects The Florida Entomologist, 69 (1) DOI: 10.2307/3494748.

13Mlot NJ, Tovey CA, & Hu DL (2011). Fire ants self-assemble into waterproof rafts to survive floods. Proceedings of the National Academy of Sciences of the United States of America, 108 (19), 7669-73 PMID: 21518911.

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The Honeybee Waggle Dance – Is it a Language?

The Dance

More than half a century ago, Karl von Frisch rocked the world of behavioral biology with his conclusion that the honeybees (Apis mellifera) can actually communicate the distance to and direction of valuable food sources through an elaborate “waggle dance.” In what later led to his receipt of the Nobel Prize in Physiology or Medicine, von Frisch determined that bees recruited by this dance used the information encoded in it to guide them directly to the remote location of the resource.

In the typical waggle dance, a foraging worker bee who has found by a rich food source returns to the hive, is greeted by other bees, and commences dancing on the vertical comb surface within the dark nest (in other species of bee, like Apis florea, the dance is performed on a horizontal surface in direct view of the sun and/or other landmarks). She dances in a figure-eight pattern, alternating “waggle runs,” during which she vigorously waggles her body from side to side in a pendulum motion at about 13 times per second as she moves forward in a straight line, with return phases in which she circles back to the approximate starting point of the previous waggle run, alternatingly between clockwise and counter-clockwise returns. Here’s a video of a bee doing the waggle dance:

As the video indicates, the honeybee’s dance encodes key information about the resource. For instance, as she performs waggle runs on the vertical comb surface, her average body angle with respect to gravity corresponds to the direction of the food source relative to the current position of the sun (the sun’s azimuth). Accordingly, if the food source lies in the exact direction of the sun, she will waggle straight upwards; if the food lies, say, 30 degrees to the right of the imaginary line to the sun, she will angle upwards 30 degrees to the right of vertical. Also, the duration of her waggling runs is directly linked to the flight distance from the hive to the food source, with (for many bee subspecies) every extra 75 milliseconds of waggling adding roughly another 100 meters to the distance. Further, the more attractive the destination, the longer and more vigorously she dances, and the more quickly she returns for the start of each waggle run. Depending on the richness of the food source, she may perform up to 100 waggle runs in a single dance.

Next week ... the Tango!

Cognitive Complexity

It seems, then, that honeybees have evolved an extraordinary complex form of symbolic communication about distant resources, one that is beyond the capabilities of virtually every other species except for humans. Not bad for an insect.

The cognitive tasks implicated by the waggle dance are not insignificant: the dancer must remember the location and characteristics of a specific site she has seen on her foraging trips, and translate this information into the appropriate dance characteristics. She must also remember and take into account the position of the sun, and update that position as the sun moves (the ability to compensate for the sun’s movement by memory has been documented by researchers observing dances over several hours of overcast weather, when there are no celestial cues to be seen). The observing bees must “read” the dance, translate their sensory input into a resource location, and then find the resource, navigating as necessary around hills, houses and other obstacles.

In fact, the feat is so stunning that von Frisch’s findings were initially met with significant skepticism and controversy.1 At this point, the controversy has essentially been settled, with scientists recognizing that there is compelling evidence that honeybees really do communicate and act on the information encoded in the waggle dance, even though uncertainty remains regarding exactly which signals (tactile, odor, vibrations, air flows, etc.) the observing bees use to translate the dance into actionable information regarding the resource location.2

Is the Waggle Dance a “Language”?

So, the waggle dance is an extremely complex communication system, but is it a language?

Eileen Crist, Associate Professor in Science and Technology in Society at Virginia Tech, makes a rather compelling case that the waggle dance embodies many of the attributes of a true language.3 After noting that the waggle dance is always performed in front of an audience and is clearly communicative in nature, she describes some of the principal features that support its being characterized as a language:

  1. Rule-Governed. If a communication system is to be considered linguistic in nature, it generally must be based on a set of rules that are structured and used with regularity. This is the case with the waggle dance: the dance is always performed in a designated place within the hive, it is never done unless an audience is present, and it always follows a standard template for conveying direction, distance, and desirability. While the general rule is that the waggle dance is to be used to inform other bees about sources of nectar, when the colony has a special requirement (e.g., locating water when the hive is overheating or finding a new home when part of the colony must relocate) then the rules dictate that the dance purpose switches to this pressing need. Also, the general rule is that foragers dance about rich, reliable and near resources, but in times of need the “dance threshold” for less desirable resources is lowered.
  2. Complexity. A key dimension of a true language is its complexity, as it is unlikely that a communication system based on just a few rules will qualify as a language. The bee dance rules are not only extremely intricate, but they are applied in a versatile and complex fashion to respond to differing environmental factors and hive requirements.
  3. Stability and Dynamism. A core feature of human language is that a relatively fixed and stable syntax enables the dynamic generation of an indefinite number of new sentences. Similarly, while the waggle dance always takes the same recognizable forms, it “accommodates different purposes, shifting circumstances, urgent needs, and unprecedented events; while structurally identical every time, it is also contextually flexible.”
  4. Symbolic. By itself, the symbolic nature of the waggle dance has led to its being called a language. The dance symbolically represents conditions existing in the real world, actually enabling human researchers to “read” the information encoded in the dance to find specific honeybee food sources and even to design experiments about honeybee foraging behavior.
  5. Performative. According to linguistic theory and as first articulated by John Austin, languages not only describe the world, they also include what he called “performative” utterances, which are used to carry out actions.4 Not only is the waggle dance symbolically descriptive, but it has performative force in the sense that it elicits action from the bees who watch it (as Crist notes, the performative nature of the waggle dance is implicit in the way in which scientists “routinely deploy a vocabulary of announcing, reporting, summoning, recruiting, soliciting, inviting, commanding, and guiding” in describing it).

James Gould, Professor of Ecology and Evolutionary Biology at Princeton University, summarized both the controversy over the issue and the nature of honeybee dance communication as follows:

Some of the resistance to the idea that honey bees possess a symbolic language seems to have arisen from a conviction that “lower” animals, and insects in particular, are too small and phylogenetically remote to be capable of “complex” behavior. There is perhaps a feeling of incongruity in that the honey bee language is symbolic and abstract, and, in terms of information capacity at least, second only to human language.5

Gould estimates that the waggle dance is capable of communicating at least 40 million unique messages (“sentences”), more than 10 times as many as any other animal except for man.6

Not surprisingly, not everyone agrees that the waggle dance constitutes a true language. For example, Stephen Anderson, Professor of Linguistics at Yale University, acknowledges that honeybee dance communication is elaborate and cognitively rich, but concludes that it is unlike human natural language in that, for example, it is genetically fixed rather than learned through environmental interactions, it lacks a syntax in which the order of the communicative elements (words or actions) impacts meaning, and there is a close correspondence between the structure of the dance signals and the nature information to be conveyed (e.g., orientation of the waggle run and the direction to the resource).7

Some bees are better at the dance than others...

To Bee or Not to Bee

In the end, there will probably always be debate and disagreement over whether the waggle dance is a true language. Clearly, the waggle dance and human language are vastly different communication systems, and how we label the waggle dance in human terms may be missing the point. From the honeybee standpoint, the dance serves its purposes and contains all of the communicative nuances that the bees need within their environment. Maybe, the real point is that we should sit back and appreciate the fact that the honeybee, a small insect with tiny brain, has been able to evolve a system of communications that is so sophisticated that it has challenged human linguists to wrestle with the question of what distinguishes a true language and whether human language is really so unique.

Anyhow, time to stop droning on and sign off!

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1See, e.g., Gould, J. (1975). Honey bee recruitment: the dance-language controversy Science, 189 (4204), 685-693 DOI: 10.1126/science.1154023.

2See, e.g., Landgraf, T., Rojas, R., Nguyen, H., Kriegel, F., & Stettin, K. (2011). Analysis of the Waggle Dance Motion of Honeybees for the Design of a Biomimetic Honeybee Robot PLoS ONE, 6 (8) DOI: 10.1371/journal.pone.0021354; Gil, M., & De Marco, R. (2010). Decoding information in the honeybee dance: revisiting the tactile hypothesis Animal Behaviour, 80 (5), 887-894 DOI: 10.1016/j.anbehav.2010.08.012.

3Crist, E. (2004). Can an Insect Speak?: The Case of the Honeybee Dance Language Social Studies of Science, 34 (1), 7-43 DOI: 10.1177/0306312704040611.

4Hymes, D. (1965). : How to Do Things with Words . John L. Austin. American Anthropologist, 67 (2), 587-588 DOI: 10.1525/aa.1965.67.2.02a00970.

5Gould, J. L. Ibid. at 692.

6Gould, J. L. Ibid. at note 37.

7Anderson, S. R. 2004. Doctor Dolittle’s delusion: Animals and the uniqueness of human language. New Haven, Conn.: Yale University Press. ISBN-13: 978-0300115253.

The Rational Ant

In a recent post I described how pigeons are better than humans at solving the Monty Hall problem and might therefore prove to be formidable competitors on Let’s Make a Deal. In this post, I have some good news and some bad news for those of you readers who are human (I make no assumptions in this blog). The good news is that I have yet to see any research showing that pigeons can triumph over humans at Jeopardy. The bad news is that the top two winners on Let’s Make a Deal could well end up being a pigeon and an ant, leaving the human contestants to go home with nothing more than an electronic version of the game (and perhaps a goat or two).

An article in ScienceNOW1 provides the backdrop:

Ants enjoying a nectar lunch on a sunny day (photo: Wikipedia)

Consider the following scenario: You want to buy a house with a big kitchen and a big yard, but there are only two homes on the market–one with a big kitchen and a small yard and the other with a small kitchen and a big yard. Studies show you’d be about 50% likely to choose either house–and either one would be a rational choice. But now, a new home comes on the market, this one with a large kitchen and no yard. This time, studies show, you’ll make an irrational decision: Even though nothing has changed with the first two houses, you’ll now favor the house with the big kitchen and small yard over the one with the small kitchen and big yard. Overall, scientists have found, people and other animals will often change their original preferences when presented with a third choice.

Not so with ants. These insects also shop for homes but not quite in the way that humans do. Solitary worker ants spread out, looking for two main features: a small entrance and a dark cavity. If an ant finds an outstanding hole–such as the inside of an acorn or a rock crevice–it recruits another scout to check it out. As more scouts like the site, the number of workers in the new hole grows. Once the crowd reaches a critical mass, the ants race back to the old nest and start carrying the queen and larvae to move the entire colony.

The article goes on to describe some research on ant decision-making conducted by Stephen Pratt, an Arizona State University behavioral ecologist, and Susan Edwards, of the Department of Ecology and Evolutionary Biology at Princeton University. In this research, published in Proceedings of the Royal Society: Biological Sciences2, Pratt and Edwards designed a series of possible nests for 26 ant colonies:

The duo cut rectangular holes in balsa wood and covered them with glass microscope slides. The researchers then drilled holes of various sizes into the glass slides and slipped plastic light filters under the glass to vary the features ants care about most. At first, the colonies only had two options, A and B. A was dark but had a large opening, whereas B was bright with a small opening. As with humans, the ants preferred both options equally: The researchers found no difference between the number of colonies that picked A versus B.

Then the scientists added a third option, called a decoy, that was similar to either A or B in one characteristic but clearly worse than both in the other (a very bright nest with a small opening, for example). Unlike humans, the ants were not tricked by the decoy, the team reports online today in the Proceedings of the Royal Society B. Although a few colonies picked the third nest, the other colonies did not start favoring A or B and still split evenly between the two.

Ants can make better decisions because they take advantage of collective wisdom and do not “overthink” their options the way humans are prone to do. As Pratt noted in an article published in PhysOrg.com3, “Typically we think having many individual options, strategies and approaches are beneficial, but irrational errors are more likely to arise when individuals make direct comparisons among options.”

This research is particularly fascinating in that it poses a direct challenge to our core belief that we will always enjoy a large advantage over other animals when there is an intellectual way to solve a problem: sure, animals may have highly-evolved senses of smell, they may be fast, they may have impressive reflexes and their instincts may be powerful, but where we humans are able to harness our large brains, we will inevitably prevail.

In fact, though, we should hold off before patting ourselves on the back. As this (and other) research shows, we suffer from biases and flaws in the way we approach thought problems that can lead to irrational decisions and that can even put us at a disadvantage vis-à-vis other animals, including the birds and the ants.

Something to think about.

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1ScienceNOW, “Can’t Decide? Ask an Ant,” July 22, 2009.

2Edwards SC, Pratt SC. Rationality in collective decision-making by ant colonies. Proc Biol Sci. 2009 October 22; 276(1673): 3655–3661, published online 2009 July 22 (doi: 10.1098/rspb.2009.0981).

3PhysOrg.com, “Ants more rational than humans,” July 24, 2009.

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