Biological fight: the case of artificial stimuli in behavior research

by Piter Kehoma Boll The study of animal behavior is an important approach to understand several aspects on the ecology and the evolution of living beings, both from the analyzed animals themselves and the species with which they interact. For example, understanding how a bee recognizes a flower as a food source and how it approaches it may explain a lot about the physiology and the evolution of the flower and vice-versa, thus clarifying why such a combination of characters is the one that is found in the current population.

As with virtually any type of study in biology, a research may be done with sampling or experiments. By sampling you obtain non-manipulated information directly from the environment. You collect or observe a small sample of the whole and infer the general situation of the population based on it. On the other hand, in an experiment you manipulate the environment and watches how the organisms will react to the different stimuli presented to them and, from this, you develop your conclusion.

For example, if you want to know what a species of frog eats, you may find out by sampling, observing some frogs in the wild while they feed or capturing some and examining their stomach contents. You may also offer them different kinds of food, either in the environment or in the lab, and observe how the frogs reacts to each one.

Thus, in experiments you control the stimuli the species receives from the environment. This is the point where things start to get nasty. May the stimuli have artificial elements, i.e., elements that cannot be found by the animal in its habitat?

The opinions about it are divergent and recently led to a “formal fight” published in the journal Ethology:

On one side is a group of researchers from several universities around the world (Hauber et al., 2015) that defends the use of artificial stimuli to analyze behavior. They use as a model the studies on the rejection of eggs of parasitic birds by parasitized birds, a well-studied phenomenon.

First, let us contextualize this phenomenon briefly:

Several bird species, mainly cuckoos, do not incubate their own eggs. Instead of doing it, they lay them in the nests of birds of other species and hope that the poor creatures incubate and later feed the chicks as if they were their own. As a result, natural selection favors cuckoos whose eggs are more similar to the ones of the parasitized bird and also favors the parasitized birds that better distinguish their eggs from the ones of the intruders. It is a typical evolutionary race.

Find the intruder. The similarity between the egg of the parasite and the parasitized can vary greatly. Photos by wikipedia user Galawebdesign (left)* and by Grüner Flip (right).

Find the intruder. The similarity between the egg of the parasite and the parasitized can vary greatly. Photos by wikipedia user Galawebdesign (left)* and by Grüner Flip (right).

In experimental studies on egg rejection by parasitized birds, it is common to use artificial eggs that exaggerate features of natural eggs. This includes, for example, changing color and size in order to understand which is the most relevant for the bird to recognize the eggs as being yours or not. However, can we trust the results of such experiments using artificial elements?

Haubert et al. (2015) think that we can. Their arguments in favor of the use of such artificial stimuli are the following:

  1. Real eggs of the studied species are difficult to get in large quantities and could cause significant impacts over the populations if used. So, artificial eggs ensure the integrity of populations.
  2. It is difficult to get a set of natural eggs similar enough to allow the necessary repetitions to validate the test. After all, a result is only considered valid if it is recorded several times in face of the same stimulus. Artificial eggs allow identical copies and, thus, true repetitions.
  3. Natural eggs vary in several aspects at the same time, such as color, size, form, texture… In artificial eggs it is possible to control these aspects and allow only one to show free variation, so isolating the influence of each one during the recognition by the bird.
  4. A variation beyond the ones found in the wild may help to find populations with different degrees of perception of strange eggs and consequently where are the sites of higher selective pressure.
Original eggs of the parasitized species painted to exaggerate color features. Photos by István Zsoldos. Extracted from Moskát et al. 2010.

Original eggs of the parasitized species painted to exaggerate color features. Photos by István Zsoldos. Extracted from Moskát et al. 2010.

Not everyone looks so favorably to such an unrestrained use of artificial stimuli. Soon after the opinion of Hauber et al. we find the reply of David C. Lahti (2015) who faces all by himself the “artificialist” army. Lahti shows some aversion to such exaggerate use of artificial elements that many times are not used in a responsible manner.

Suggesting a more restrict use of artificial elements, he argues the following:

  1. Our perception of the environment is different from the one of the species we are studying. For instance, a bird sees a much wider range of colors than we do. When we paint an artificial egg black and white in order to simulate a natural black and white egg, we don’t know whether the bird really sees both eggs with the same colors. So, while we suppose that the eggs look similar by our perception, the reality from the bird’s point of view can be very different.
  2. When we try to create a set of artificial eggs that vary in only one aspect, such as the size of the spots on the shell, for instance, in order to control the influence of this stimulus only, we always end up including secondary stimuli that are not measured, such as the paint used to make the spots. If the birds shows a different response to eggs with small spots (natural ones) when compared to eggs with large spots (artificial ones), how can we know that the difference was not caused by the perception of the paint, either chemically or visually, by the animal? It would be necessary to perform tests that would discard this possibility, but it does not happen usually.
  3. Exaggerated artificial stimuli may go beyond the species’ range of recognition. An egg with a color too different from any color variation found in the environment could cause the bird not to see it as an egg, which would lead to problems in the interpretation of the results.

Concerning this last argument, Hauber et al. emphasize that is important to take care on a priori interpretations on the species behavior. That is to say, we cannot guess what the bird is thinking. The fact that the bird removes the parasite’s eggs from the nest or not does not mean that it is capable of recognize the egg as an intruder, or even as an egg. The way the bird interprets the stimulus is not as important as its response to it.

Therefore, we can conclude that artificial stimuli can be advantageous and in several circumstances they are the only available alternative. It is important, however, to take care with their use and try to be sure that secondary features, generally neglected, are not considered important by the animal.

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Hauber, M.; Tong, L.; Bán, M.; Croston, R.; Grim, T.; Waterhouse, G.; Shawkey, M.; Barron, A.; & Moskát, C. 2015. The Value of Artificial Stimuli in Behavioral Research: Making the Case for Egg Rejection Studies in Avian Brood Parasitism Ethology, 121 (6), 521-528 DOI: 10.1111/eth.12359

Lahti, D. 2015. The Limits of Artificial Stimuli in Behavioral Research: The Umwelt Gamble Ethology, 121 (6), 529-537 DOI: 10.1111/eth.12361

Moskat, C.; Ban, M.; Szekely, T.; Komdeur, J.; Lucassen, R.; van Boheemen, L.; & Hauber, M. 2010. Discordancy or template-based recognition? Dissecting the cognitive basis of the rejection of foreign eggs in hosts of avian brood parasites Journal of Experimental Biology, 213 (11), 1976-1983 DOI: 10.1242/​jeb.040394

– – –

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Friday Fellow: ‘Orange Jaguar Snail’

by Piter Kehoma Boll

ResearchBlogging.orgLast week I introduced a land planarian that feeds on land snails, Obama ladislavii, or, as I called it, the Ladislau’s flatworm. Therefore, today, I thought it would be great to present a similar situation occurring backwards: a land snail that feeds on land planarians.

So let me introduce this little predator, the land snail Rectartemon depressus. Again, it is not a widely known species and thus it has no common names, but why not call it the ‘orange jaguar snail’? Species of the genus Euglandina, which are also predatory snails, are called ‘wolf snails’ by comparing them to a common predator in North America. As Rectartemon species are common in South America, we could perfectly call them ‘jaguar snails’, right?

Rectartemon depressus about to capture a land planarian Obama marmorata. Photo from Lemos et al., 2012

Rectartemon depressus about to capture a land planarian Obama marmorata. Photo extracted from Lemos et al., 2012

Found in areas of Atlantic Rainforest in Brazil, the orange jaguar snail has a yellow to orange body and a whitish shell. It is listed a vulnerable species in the Brazilian Red List, but it is not mentioned in the IUCN’s Red List.

Initially known as a predator of other land gastropods, the orange jaguar snail revealed a new item in its diet recently. During attempts to find the food items in the diet of some land planarians from southern Brazil, the orange jaguar snail was offered as a food option, but while the expectations were that the planarian would eat the snail, the opposite happened! After contacting the land planarian, the snail simply grasps it with its radula (the snail’s toothed tongue) and sucks it in very quickly, just as if it were eating a noodle!

The orange jaguar snail eagerly consumes several land planarians, both native and exotic species. It makes it one of the first known predators of land planarians. One of its prey is the Ladislau’s flatworm, so we have a snail that eats a flatworm that eats snails!

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Lemos, V., Canello, R., & Leal-Zanchet, A. 2012. Carnivore mollusks as natural enemies of invasive land flatworms. Annals of Applied Biology, 161 (2), 127-131 DOI: 10.1111/j.1744-7348.2012.00556.x

Santos, S. B., Miyahira, I. C., Mansur, M. C. D. 2013. Freshwater and terrestrial molluscs in Brasil: current status of knowledge and conservation. Tentacle, 21, 40-42.

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Tunnel of Time #1: Evolution – The Game of Intelligent Life

by Carlos Augusto Chamarelli

Hey everybody, PK here as usual. Today I’ll present the first of Tunnel of Time’s articles, where we shall remember and discover some of the multimedia works we’ve seen published around the world, including games, movies, documentaries, books, magazines, computer programs and anything related to biology or general sciences, influencing us and making our imagination take flight, and of course, entertaining us as they do.

Our first Tunnel of Time item will be the game primarily responsible for my interest on Earth’s history and the evolution of living beings: Evolution – The Game of Intelligent Life. Initially developed by Crossover Technologies and Discovery Multimedia in 1997, it was released in Brazil under the name “Evolução – o Jogo da Vida” the following year, under Globo Multimídia, completely translated to Portuguese. To this day I remember the day I gazed upon it’s peculiar box at the Nova America’s computer shop, nowadays a clothes store with ugly T-shirts where its noble box once stood.

A shirt with this picture wouldn’t be so bad.

A shirt with this picture wouldn’t be so bad.

The game is a blend of simulation and strategy, and players have the option to play on historic Earth or a randomly generated world, also allowing to choose its length, from short scenarios focusing on a single periods or the complete history of land vertebrates, from early tetrapods 360 million years ago to the appearance of intelligent species – the final objective of the game – with a single second representing 30 thousand years.

Few people know, but dinosaurs appeared during the early Permian and survived to this day on Africa.

Few people know, but dinosaurs appeared during the early Permian and survived to this day on Africa.

There are around 170 species, ranging from famous ones such as wooly mammoths and the Tyrannosaurus, as well as others – at the time of its release, that is – less known, such as Indricotherium and Ventastega. There are also intelligent species other than Homo sapiens, created by the developers in order to offer more variety and explore possibilities, such as Elephasapiens, an intelligent elephant, and the Saurosapiens, evolved from dinosaurs; so not only this game inspired me to the general idea of evolution, in a way it also my first ever contact with speculative evolution. There’s an in-game Bestiary, bringing informative texts about each creature, also explaining some of the decisions and exploration of ideas subtly introduced, such as synapsids and anapsids reptiles able to evolve into dinosaurs (in-game incentivized to be seen as analog species if an alternative path of evolution was taken) and the possibility of other animals being candidates to originate intelligent species.

And they STILL don’t get any pleasure from artistic pursuits.

And they STILL don’t get any pleasure from artistic pursuits.

The game is either played alone or against 5 opponents (computer or human controlled), but even on yourself the game is plenty challenging as continents move, climates change and the environments are altered and you need to evolve your creatures so they can keep up with the times – though not something easy, you can also go against it and see how long you can make an species survive, such as Pantylus enduring the Carboniferous all the way to the Cenozoic; it’s hard not to feel proud of the little guys. Each creature have an time period and specific ambient where they survive and feed better, thereof it’s imperative you take possession of the best feeding regions before your enemies do. When evolving new creatures you must allocate points that dictate how fast you evolved – determinate by how well you creature’s population are doing – , how much your feeding will improve and how fit for combat it is, offensively or defensively, this last point coming more into play in multiple players matches, as predator species are your main tools to maintain control of your territories and chase invaders away. As if it wasn’t enough the fight for survival among creatures, there are also natural disasters, causing mass extinctions and sometimes even altering the global climate to challenge you even more.

You’ll have to excuse the oddly outdated swamp-dwelling Diplodocus; At least it’s not dragging its tail.

You’ll have to excuse the oddly outdated swamp-dwelling Diplodocus; At least it’s not dragging its tail.

The game shipped with a Tree of Life poster, containing all the creatures of the game and the evolutionary lines, and a printed version of the Bestiary with higher-res versions of the creature’s graphics in all their 90’s 3D graphics glory. The Brazilian release only came with the poster (good grief), but it’s all good, to this day I keep it safe so one day I can frame it and put on a wall. The game manual, as per tradition of games released on that decade, contained additional information, in special the notes of designer Greg Costikyan regarding the decisions taken in the game’s development, such as the limitations of the time it was made forcing a rigorous selection of species that could offer a good variety of creatures and still create an evolutionary tree analogous to that of real life; all whilst fitting inside a CD-ROM.

Although with slow-paced playability – something that doesn’t attract as many people as first person shooters–, it’s to this day one of my all-time favorites, despite only able to run on Windows 98 and previous OS without the help of modifications. Before this game my knowledge about Earth’s past was limited to dinosaurs and what was taught at school like human history, so I’m happy I could get a hold of it when I did, and I’m thankful in all sincerity for those that were responsible for this project.

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Friday Fellow: ‘Ladislau’s Flatworm’

ResearchBlogging.orgby Piter Kehoma Boll

Friday fellow is back!

After almost a year, I decided to go on with it. Actually, I interrupted it because of several other activities that were requiring my attention. Now let’s move on!

Today I will present to you another land planarian, and one I particularly like. Its binominal name is Obama ladislavii (formerly Geoplana ladislavii) and, as most land planarians, it does not have a popular name, although I suggest it to be ‘Ladislau’s Obama’ or ‘Ladislau’s Flatworm’. Now who is Ladislau?

Well, let’s first take a look at how this species was first described.

The Ladislau’s Flatworm was described in 1899 by the zoologist Ludwig von Graff in his famous monograph, “Monographie der Turbellarien”. Graff described it based on specimens sent to him from southern Brazil by the zoologist Hermann von Ihering, as well as on other specimens collected by the biologist Fritz Müller.

By the time Ihering and Müller were collecting specimens in Brazil, a botanist named Ladislau de Souza Mello Netto was the director of the Brazilian National Museum in Rio de Janeiro. He actually hired them as traveling naturalists, so we can say that he was the responsible for them being able to collect specimens in Brazil.

As a result, when describing this new planarian species, Graff decided to call it ladislavii in honor of Ladislau Netto. At least I think so! I did not find any reference to that, as Graff did not explain the etymology of the name in the description. However, whom else would ladislavii be referring to?

Now that we explained the name, it is time to talk about the worm itself.

Ladislau’s flatworm is found in southern Brazil’s states of Rio Grande do Sul and Santa Catarina and is easily recognized by its green color. The larger specimens can measure more than 10 cm in length and more than 1 cm in breadth while creeping, so it is a considerably large planarian for the local standards.

Obama ladislavii in all of its greenness. Photo by Piter K. Boll*

Obama ladislavii in all of its greenness. Photo by Piter K. Boll*

Most land planarians are found either in very well preserved ecosystems, for example, inside undisturbed forests, or in very well disturbed ecosystems, such as gardens and urban parks. Now we can find the Ladislau’s flatworm living very well both in a natural paradise in the middle of a dense forest as well as in that small garden beside a very busy street. How is that possible?

The life history of many land planarian species is completely unknown, so that we do not even know what they eat. They are recognized as important predators of other invertebrates, but that is not enough, as being a predator does not mean that you eat anything that moves, right?

Until recently, we knew very little about the Ladislau’s flatworm, but I started to study it along with other species in the last years and so now we at least have an idea of what it eats, and the answer is: Gastropods, i.e., slugs and snails!

We usually found gastropods in gardens, parks, plantations and everywhere humans plant something, so they are an available meal for the Ladislau’s flatworm. It feeds on many of those annoying little pests you may find in your garden, including the garden snail (Helix aspersa), the Asian trampsnail (Bradybaena similaris), and the marsh slug (Deroceras laeve).

Obama ladislavii and one of its snacks, the snail Bradybaena similaris

Obama ladislavii and one of its snacks, the snail Bradybaena similaris. Photo by Piter K. Boll*

The Ladislau’s flatworm can follow the slime trail left by the gastropod in order to find and capture it. The most efficient way for the planarian to subjugate the prey is by surrounding it with its body and using muscular power, not very different from what a constrictor snake does.

Considering its taste for those pests, the Ladislau’s flatworm seems to be a good item to have in your garden, right? Yes, but only if you live in southern Brazil. Exporting it to other areas can lead to catastrophic results, as the case you can read here.

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Boll, P., & Leal-Zanchet, A. (2014). Predation on invasive land gastropods by a Neotropical land planarian Journal of Natural History, 1-12 DOI: 10.1080/00222933.2014.981312

Graff, L. v. 1899. Monographie der Turbellarien. II. Tricladida Terricola. Engelmann, Leipzig, 574 p.

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Pooping to evolve: how feces allowed us to exist

by Piter Kehoma Boll

ResearchBlogging.orgBillions of years ago, when the first lifeforms appeared on Earth, our planet was very different from what it is today. Oxygen, so essential for our survival, was not present in the atmosphere.

Thanks to the appearance of the first photosynthetic bacteria, the so-called Cyanobacteria or blue-green algae, our atmosphere started to accumulate oxygen. As you may know, photosynthesis is a process by which plants and other photosynthetic organisms convert water and carbon dioxide into oxygen and organic compounds.

Oxygen is a very reactive element, so it can easily interact with other compounds and is great to burn organic matter to release energy. Without oxygen, heterotrophic life, such as animals, would not be able to use large quantities of energy and therefore would have never been able to achieve large size.

As you may also know, animals most likely appeared in the oceans and only much later conquered the land. However, oxygen produced by photosynthesis accumulates mainly in the atmosphere and not in the oceans. Today, only 1% of the global oxygen is found in the oceans, and it was even worse during the first million years of multicellular life. Do you know why?

The most primitive animals alive today are sponges, which are quite different from other animals. They usually have a hollow body with several pores, which function as tiny mouths through which water carrying small planktonic organisms and other organic matter is pulled inwards and later released by a large opening on the top of the body. So the main thing sponges do is mixing water and extracting a small amount of organic matter from the water column. Their feces, when returning to the water, are not very different in size from the organic matter they initially ingested.

Sponges ingest organic particles and release organic particles. They are not very efficient in removing organic matter from water.

Sponges ingest organic particles and release organic particles. They are not very efficient in removing organic matter from water.

Thus, in a sponge-only world, the water column was possibly always crowded with dissolved organic matter. This was a feast for bacteria, which are always eager to decompose organic matter and, while doing so, they consume large amounts of oxygen. Therefore, water with high amounts of organic matter increases bacterial activity and turns the environment anoxic, i.e., without oxygen. As a result, there was no oxygen available to allow animals to become large.

Despite not growing very much, animals were still evolving, of course, and eventually the bilaterian animals appeared. Bilaterian animals have a bilateral symmetry and, the most important feature in this story, a gut. It means they ingest food, digest it, process it and later eliminate the rests as… poop! In the gut, feces become compact as fecal pellets and sink much quickly to the bottom of the ocean, cleaning the water column from organic matter and drastically reducing bacterial activity. With no bacteria decomposing in the water column, the oxygen levels rapidly started to increase, allowing animals to grow and things like fish to evolve.

Bilaterian animals produce compact fecal pellets which sink to the bottom, cleaning the water column.

Bilaterian animals produce compact fecal pellets which sink to the bottom, cleaning the water column.

If animals had never started to poop, we most likely would have never been able to arise in this world. Long live the poop!

– – –


Holland, H. (2006). The oxygenation of the atmosphere and oceans. Philosophical Transactions of the Royal Society B: Biological Sciences, 361 (1470), 903-915 DOI: 10.1098/rstb.2006.1838

Turner, J. T. (2002). Zooplankton fecal pellets, marine snow and
sinking phytoplankton blooms. Aquatic Microbial Ecology, 27, 57-102

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Review: The Paleoart of Julius Csotonyi

By Carlos Augusto Chamarelli

Hi everybody! PK here and it’s book-reviewing time! As you probably know by now, Titan Books has released another tome of paleoart earlier this year in May 20, and once again Earthling Nature was offered a chance to get a copy and review it for everyone’s delight. What happened, however, is that the timing was a much unfortunate one with the World Cup messing absolutely everything in Rio, so I haven’t actually received my copy yet (at the time of this writing), but I did receive things that were posted in May these days, so I’m still hopeful.

Fortunately, I have a PDF version which I could read while waiting, so my impressions written here are based on that; it just means I can’t praise the paper and illustration quality and such as much as I did previously, but bear with me anyways.

Dinosaur attacks are mandatory for paleoart covers.

Dinosaur attacks are mandatory for paleoart covers.

The new book in question, entitled The Paleoart of Julius Csotonyi, is a little reminiscent of Titan’s previous book on paleoart, Dinosaur Art – The World’s Greatest Paleoart, released in 2012 (and which you can view our critique right here), the difference being that instead of being a collection of works from 10 paleoartists, this time it focuses solely on the art – and some biography – of one of them: the Hungarian-born, Canadian-raised artist Julius Csotonyi. You know, like it’s said in the title.

I’ll start right off the bat saying that Csotonyi’s work is much impressive and definitely was one of the highlights of Dinosaur Art, so I think he is indeed one of the prime choices for a book solely focused on his work, and the text also provide interesting insights on these works as well as rather inspirational accounts of his rise to paleoartistic success. I mean, creating dinosaur murals for a museum? That’s some paleoart-nirvana right there.

Also, this picture. Nothing else needs to be said.

Also, this picture. Nothing else needs to be said.

Like Dinosaur Art, the book is full with beautiful artworks depicting prehistoric life from many time periods, some small and some spreading though pages as they should be to enjoy the details, plus there are examples of the usual start in childhood at dinosaur drawing in the beginning of it all, but what caught my attention the most was the presence of step-by-step pictures, showing the process of making a bunch of confusing lines like those of sketches become the saurian-masterpiece everyone loves. For those unfamiliar with Csotonyi ‘s style, he uses mostly digital tools, like a good modern paleoartist usually does; sometimes he uses brushes for a more traditional look, sometimes photomanipulation to achieve more realism, but the resulting picture always have that particular look and can be instantly recognized.

Mostly the reconstructed creatures possess striking patterns, but not striking colors; that, to me, is a key difference when dealing with realism with dinosaurs, and usually the more an artist make huge dinosaur colorful the less I’m inclined to judge their work as a reliable window to prehistoric life*. In this respect, Csotonyi achieves a good balance in the tone of colors, so the animals are neither boring nor garish to behold. The scenes depicted throughout the book vary, with some in the school of “dramatic prehistoric conflict”, others are more neutral and peaceful, and there are some which are anatomy and bones studies, so there’s something for every taste. It’s also worth noting that Csotonyi actually revisits older pictures and update their looks, as it was the case of the Anchiornis, which is important as depictions of dinosaurs will invariably change,and editing then as such is a good manner to make your picture still relevant.

Reenactment of Jaws Included.

Reenactment of Jaws Included.

I do have one or two points that I personally have mixed feelings about : the pictures where he uses actual photos for the landscape aren’t as good as those where he actually makes the scenery, and I understand it’s easier to do that than making the entire scene, but in some of these cases the shadows of the animals get a little in the eye, and it looks too much like the creature was in fact inserted into the scene rather than being part of it. On another point, some of the skins used in the photo manipulations can be a little jarring; the Edaphosaurus with a tuatara’s scaly skin and face being a good example of this. Then again, those can be regarded as very minor points as they don’t detract of the overall quality, so I’m not one bit bothered, and neither should you, as the book remains a incredible piece.

"Alright, alright! You can keep it! Geez."

“Alright, alright! You can keep it! Geez.”

In closing thoughts, The Paleoart of Julius Csotonyi is yet another excellent book for everyone interested in dinosaurs and prehistoric life, depicted here in an evocative but not in a “dinosaurs are monsters” light, and it’s definitely worth checking. I promise that when (if) I get my copy I’ll update this review. Also, you can click here to go to his website give him a good ol’ Iguanodon thumbs-up.


*And don’t give me the “oh, but birds are dinosaurs, and they’re colorful, so dinosaurs must have been ALL colorful!” BS. It’s just embarrassing.

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The polyglot bee

by Piter Kehoma Boll

ResearchBlogging.orgCommunication is essential for humans, and so it is for other animals that live in groups. It is intersting that even though modern humans only came to be about 200,000 years ago, the number of languages which evolved in our species since then is huge. And two people who speak different languages usually cannot understand each other. Even simple hand gestures, like the beckoning sign, meaning “come here”, is rather different between cultures. Most of our communication is not inherited, but rather learned.

Three different ways to say “come here” with gestures. The first two are western style and the last is eastern style. Photos taken from (left), (center) and (right).

Three different ways to say “come here” with gestures. The first two are western style and the last is eastern style. Photos taken from (left), (center) and (right).

But what about communication in other animals? Is it possible that different languages evolve in separate populations so that one group cannot understand what the other is saying?

One well-known and well-studied form of communication in animals is the honeybee waggle dance, used by honeybees to indicate the location of a food source to others. This dance informs the direction and distance of the food source from the hive in order to guide other bees to the right spot.


Scheme of the bee waggle dance. Picture by Wikimedia Common’s user Audriusa.*

Scheme of the bee waggle dance. Picture by Wikimedia Commons’ user Audriusa.*

Basically, what the bee does is to move in a path forming an 8-shaped figure. The angle of the dance in relation to the hive’s orientation indicates the angle of the food source in relation to the sun. The middle part of the dance, which represents the part where the two loops of the 8 overlap, is done with a frenetic waggle. The duration of this waggle part of the dance informs the distance of the food source from the hive.

There are many subspecies of honeybees and the waggle dance may have become different in each of them by evolution, creating different dance languages or dialects. It’s difficult, however, to compare those dialects because they can be adjusted to different conditions in the environment, so two hives must be in the very same environment to be compared. The best way to compare differences would be rearing different bee species in the same hive. But that is difficult because bees tend to attack foreigners as they are easily identified by smell.

Yet after some attempts, a group of scientists from Zhejiang University in China was able to create some mixed hives of European honeybees (Apis mellifera ligustica) and Asian honeybees (Apis cerana cerana). They observed the behavior of individuals from both species in the hive in order to find differences between their dances and how they communicate with each other.

Appis cerana cerana (left) and Apis mellifera ligustica (right). Photos by Wikimedia Commons' User Viriditas* (left) and Charles Lam* (right). Extracted from commons.wikimedia,org

Apis cerana cerana (left) and Apis mellifera ligustica (right). Photos by Wikimedia Commons’ User Viriditas* (left) and by Charles Lam** (right). Extracted from commons.wikimedia,org

The results were impressive. The dances were rather different for each species, but bees retained part of their original dance in mixed hives and changed other part. There was no difference in communicating the direction of food between the species when reared in the mixed hive, but Asian bees showed longer waggle duration than European bees to inform the same distance. Nevertheless, both species were able to understand the dance from individuals of the other species and reach the food source without trouble. Even when another food source in the same direction was closer to the hive, bees chose the more distant source informed in the dance.

It seems then that bees are excellent at understanding foreign languages, but not as good at “speaking” them. They retain a strong accent, but are able to be understood anyway.

Moreover, even though European and Asian bees are estimated to have diverged more than six million years ago, they still can understand each other. This indicates that the waggle dance is a quite conserved behavior.

The waggle dance seems to have a possible genetic part, such as the duration of the waggle, since it wasn’t affected by the mixed environment. But it also has a learned part, such as the information about the direction of food.

Those results raise good questions and indicate a path to follow to study and better understand social learning, i.e., learning from information gathered from other individuals rather than by personal experience.

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Su, S.; Cai, F.; Si, A.; Zhang, S.; Tautz, J. & Chen, S. 2008. East Learns from West: Asiatic Honeybees Can Understand Dance Language of European Honeybees PLoS ONE, 3 (6) DOI: 10.1371/journal.pone.0002365

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