Scientists have thought for a decade that iron-bearing structures in the homing pigeon’s beak help the bird find its location by “reading” Earth’s magnetic field. Now, it turns out that this iron occupies cells that battle infection, rather than nerve cells.

Oops!

The new results leave a chasm in our understanding of bird navigation, says Charles Walcott, an expert on the subject at Cornell University, who was not involved in the study. “It’s astonishing that we have what seems like a terribly simple-minded problem. Take a homing pigeon any direction, and after circling a couple of times, it heads for home … and we don’t understand how these animals do this?”

Study leader David Keays, of the Institute for Molecular Pathology in Vienna, did not set out to debunk a beautiful theory, but rather to explore the nerve cells in the beak that supposedly register magnetism. “My background is in molecular biology and genetics, and I thought there must be some incredible biology involved. I wanted to get a handle on the molecules and create an artificial receptor.”

Because the “magnetic neurons” in the beak contained iron, Keays applied a blue stain that gloms onto iron. Christoph Treiber and Marion Salzer generated one-quarter million slices for microscope slides, each one-hundredth of a millimeter thick.

(Makes us dizzy … Didn’t they outlaw slavery?)

A fly in the ointment!

Although the magnetic neurons were said to number just six, iron-rich cells showed up all over the beak. One beak had about 108,000 blue-stained cells while another had just 200, Keays says. “This did not make sense. If these were magnetoreceptors, we would expect a similar number in birds of the same age and sex.”

When the scientists treated the samples with stains that attach to neurons, there was almost no overlap with the iron-bearing areas.

As questions accumulated, the researchers got a lucky break. One bird’s infected beak attracted blue cells that resembled macrophages, immune cells that fight infection (and also process iron). “You could see the cells’ tentacles engulfing other cells,” Keays says.

Stains that attach to immune cells overlapped heavily with the iron stain, Keays says; further evidence that the iron was inside macrophages, not neurons.

The study is “quite interesting and convincing,” says Walcott, and it explains why scientists have found no connection between the iron crystals and the nervous system. “If this is going to be seen as a sense organ, I think the two ought to be connected.”

Paradigm paranoia

Although the new study overthrows the accepted explanation for the pigeon’s magnetic mastery, Walcott says magnetism isn’t the whole story in navigation; birds also use vision, memory and smell.

Looking at the sun can help the bird figure out direction, but magnetic methods are needed to find a location on the globe.

Confusingly, birds seem to have a mechanism in the eye that detects Earth’s magnetic field. But because this works only when the sun is shining, it’s unlikely to explain nighttime navigation.

Keays says attitudes have changed since he “released a cat among the pigeons” at a conference a year ago. “Half of the audience wanted to hug me, they had been very skeptical, but the other half wanted to kill me.”

Since then, however, “We were able to persuade some big players in the field that the original reports were wrong. I think the great thing about science is that it is a self-correcting enterprise. If we get it wrong, somebody is going to come along and work out what the truth is.”

At this point, though, mystery rules. “It’s absolutely clear that birds, pigeons, can detect magnetic fields,” Keays says, “but the way they do that is the mystery.”

As honeybee colonies in the United States and Europe continue to suffer from a mysterious syndrome called colony collapse disorder (CCD), scientists are scrambling for answers. Another answer arrived this week, with a publication¹ that implicates a widely used insecticide.

CCD endangers many crops, but none more than almonds, which are pollinated by bees in more than a million hives trucked to California during the flowering season. Trucking stresses the bees, and stress is one of several likely contributors to the collapse syndrome.

Indeed, CCD could be several conditions lumped under one name, but here’s the trademark: The bees die away from the hive, obscuring the cause or causes of the collapse.

In the new study, scientists in France glued radio frequency identification tags to bees. Half were fed non-lethal doses of thiamethoxam, a common insecticide, then all the bees were released 1 kilometer from the hive. At the hive, the scientists used a radio-frequency gizmo to count how many flew home.

The tags did not affect the results, says Mickaël Henry, a researcher at the French National Institute for Agricultural Research, in Avignon. “Previous studies have shown that they do not impair movement or behavior of bees, or their time budgets for foraging activity.”

In any case, the control bees also sported tags.

What’s wrong?

How did the insecticide reduce the return rate so significantly? Most likely by causing difficulties with orientation, or locomotor activity, or both, Henry says.

When the experiment was repeated over a distance of just 70 meters, 92 percent of exposed and 98 percent of control bees returned, so both sets of bees were able to fly. The major impairment of exposed bees on the unfamiliar, longer route suggests that the insecticide was most damaging to the ability to learn a new route.

The neonicotinoid insecticides, the category that includes thiamethoxam, trigger nicotinic acetylcholine receptors, which are normally excited by a signal from a neurotransmitter. According to the new study, “Effects of sublethal neonicotinoid exposures in honey bees may include abnormal foraging activity, reduced olfactory memory and learning performance, and possibly impaired orientation.”

These insecticides make bees stupid, in other words.

The experiment was designed to count how many bees failed to return rather than pinpoint the reasons for that failure, Henry stresses. “The next step is to go into deeper detail about the behavior, with time-activity budgets, and looking at their foraging.”

Not the whole story

“This is a nice study, and it does clarify something that a lot of people have pointed to in the disappearance of bees,” says Phil Pellitteri, a faculty associate in entomology at the University of Wisconsin-Madison. “Insecticides have been known to cause bees to get lost, that’s one symptom of collapse. But colony collapse is a complex thing, and you can’t hang it all on one factor.”

Honeybees have long been attacked by viruses, protozoans and mites, Pellitteri says, and pesticides may decrease immunity, thus increasing susceptibility to pathogens. These, combined with the stress of long-distance travel and the scarcity of natural foraging grounds “are the general direction a lot of CCD research is pointing to. It’s a number of things, and their interactions.”

Henry and colleagues fed their data on return rates into a mathematical model, which predicted a perilous slide in colony populations. “The disappearances we observed may cause the colony to reach a population size low enough to be sensitive to other stressors,” he says. “Most bees are exposed to pesticides, and this confirms that exposure can put the colony at risk of collapse; this is the take-home message.”

If you’ve hung around a big-city park, you may think that pigeons are countless — or uncountable. But according to scientists from New Zealand, pigeons now join the short list of animals that can count — or at least, can places images containing two countable items in numerical order.

It’s blue news for those who think only humans deserve human capacities. From empathy and altruism to murder and war, animals seem to have caught on to some of our best — and worst — tricks.

Now Damian Scarf, a post-doctoral researcher at the University of Otago, with his colleagues, has taught three pigeons to order pairs of numbers in the range from one through nine.

This is not exactly counting, but it certainly is a sign of numerical awareness in birds.

More important, the researchers have taught these retired racing pigeons the concept of smaller-to-larger, Scarf says. “Previously, this number abstraction was only known in primates, and now we have shown that it is not unique to primates.”

Serious screen-time serves science

The experiment began with a year-long training period, during which the birds were shown pairs of images, each containing one, two or three countable items. If the birds pecked at both images, smaller number first, they were rewarded with some wheat. (Although the images never contained a numeral, we refer to the “number” they contain for brevity.)

To prevent the birds from focusing on color, shape or other non-numerical details, the images showed a range of items, so that the only correct answer would reflect their number rather than other distinctions.

“The training time reflects how difficult it is for them to abstract,” Scarf says. “It’s such a foreign situation, number is not the first port of call when presented with a stimulus to discriminate. That’s why we had so many shapes, colors, surface areas.”

Even if the birds originally made their judgments based on color, “we pushed them to use a different strategy, to break away from that. Number is not the default discrimination mechanism” for pigeons, says Scarf, who worked under advisor Michael Colombo of Otago.

A genius for abstraction?

This does not mean that the birds are counting, says Scarf. “It’s more a fuzzy representation in the brain of what ‘three’ is. We can apply this verbal label to three, but they cannot. Pigeons, and animals in general, don’t have a definite idea of a number, that’s why they don’t perform perfectly, and why we see the distance effect.”

When the numbers on the test pair are further apart, Scarf found, “the fuzziness overlaps a little less.”

A greater distance between the numbers produced a quicker response and greater accuracy. For adjacent numbers, like four and five, the birds scored about 66 percent accuracy, compared to more than 95 percent for numbers separated by at least six. Once the difference rose to at least three, the pigeons did as well as monkeys in a path-breaking 1998 study that opened the field of numerical “thinking” in animals.

Scarf stresses that the birds were not just regurgitating what they had learned, but were learning numerical rules. “The goal was to find out whether they could acquire an abstract rule. We were just training for one through three, but they learned some flexibility, an abstract, ascending rule for ordering numbers” that would apply to other numbers on the screen.

Rooted in evolution, but where?

Being able to recognize that one thing is more numerous than another could help an animal survive, Scarf says. “When food is available in multiple places, an animal has to develop an optimal strategy for figuring out where the most food is, and I think we have subverted that capacity for this task.”

Where this capacity arose is anybody’s guess at this point. The evolutionary lineage of mammals and birds divided about 300 million year ago, Scarf says. “If this derived from a common ancestor, it’s very old. It’s also possible that primates and birds have evolved this independently.”

“I do think it’s important, just as our study of mirror self-recognition in monkeys, from the fundamental standpoint of how these abilities come about,” says Luis Populin, a professor of anatomy at the University of Wisconsin-Madison, who has found that, under certain conditions, monkeys can recognize themselves in a mirror. “It’s very nice and is yet another step toward understanding how our cognitive functions develop.”

You have to hand it to these birds, which have set a new standard for avian aptitude. “The new part is the idea that this abstraction of numbers is not tied to training,” says Scarf. “Most numerical tests with animals involve training and testing with the same numbers, but we were training with a limited set of numbers and testing them with numbers outside the range. They learned an abstract rule, and that’s what makes this study unique.”

If you think slavery has been abolished, consider the case of the gypsy moth and the virus. For more than 100 years, people have noticed that some gypsy moth caterpillars climb to the top of trees before they die and decompose, or “melt.”

Melting releases more virus particles and is the normal fate of these caterpillars, but why did only some caterpillars perform this ascending death march?

Gypsy moths are voracious insects that have been spreading across the United States for a more than a century, so nobody is feeling too sorry for them, especially people who have seen them strip forests bare.

Still, it’s nice to read a good explanation for this peculiar “climb, croak, melt” behavior.

All the better to infect you with, my dear!

A study published today identifies a viral gene that blocks one stage of maturation in gypsy moth caterpillars, which normally hide during the day. But when Kelli Hoover, a professor of entomology at Penn State, and her colleagues infected bottled caterpillars with the virus of doom, the caterpillars showed the same climbing ‘n’ dying behavior that appears in the field.

In nature, those caterpillars would melt and then rain virus down to infect other gypsy moths.

The moth misbegotten

Gypsy moths were introduced to Massachusetts in the late 1800s by a bumbler who wanted to raise silk by crossbreeding them with silkworms — a different species, says Hoover. “It was crazy; this guy did not know anything about species, apparently.”

Still, the gypsy moths did bring fecundity and a ferocious appetite to the table — or forest. “They eat so many different kinds of trees and plants … in a bad outbreak, the insect frass dropping down sounds like rain, so you need a hat,” Hoover says.

We had to look it up to be sure, but frass is basically insect poop.

Gypsy moths are such effective defoliators that authorities try to control them with Bt, a bacterial spray that unfortunately kills beneficial insects, not just harmful ones.

Hoover’s study focused on a viral gene called egt, which inactivates a hormone that starts molting – a process that ends each stage, or “instar,” of the caterpillar’s development. “When they stop molting, they keep feeding, and that’s why we looked at egt,” Hoover says.

Photo: USDA APHIS Pest Survey Detection and Exclusion Laboratory

The battle against gypsy moths was joined before 1900, when an unknown chemical was sprayed against the invader.

ENLARGE

A dangerous meal

In every case, Hoover says, “if the gene was active, the moth died at the top of the bottle. If the gene was inactivated, it died at the bottom.”

It’s not clear, Hoover says, exactly why the gene changes behavior, but this is the first time it was traced to a single gene.

Because LdMNPV (the Lymantria dispar nucleopolyhedrovirus) infects only gypsy moths, and kill them at a young age, it might work as a biocontrol agent against a disastrous insect invasion. However, Hoover says, “the experiment’s goal was more basic – to understand how the virus enslaves its host.”

Certainly there is evolutionary logic behind changing your host’s behavior for your own benefit, assuming you are a pathogen or parasite, and “body-snatching” is well-known. For example, a fungus forces ants to climb, zombie-like, and die where they can easily spread fungal spores.

And it’s not just insects. The rabies virus, Hoover adds, “causes dogs, raccoons and bats to become more aggressive, to be out during the day, where they approach people and try to bite them,” which spreads the virus even though it endangers the animal.

And toxoplasmosis, a parasite, can make mice less fearful of cats, Hoover says, “so they are more likely to get eaten and infect the cat.”

There is even speculation that toxoplasmosis may cause men to behave with greater jealousy, Hoover says, “but the only thing that’s really been looked at is that mice with toxoplasmosis have a higher level of dopamine,” a feel-good neurotransmitter.

Is slavery therefore not all drudgery?

— David J. Tenenbaum

Image: M.J. Grimson & R.L. Blanton

The single-celled amoeba Dictyostelium discoideum has no brain, but its complicated social cycle enables farming.

Amoeba, single-cell, shape-shifters that eat bacteria and live in the dirt, don’t get much respect. When they run out of food, they gang up and move their sorry selves to greener pastures.

Pastures with edible bacteria, that is.

If ever a creature needed re-branding, this is it.

Could labeling amoeba as farmers boost their brand? In the human realm, farming gave rise to cities, writing, metallurgy and the computer in front of your face.

Amoeba don’t use the Internet. And although they do have a cell nucleus, nobody claims they have an ounce of smarts.

But now we know that some amoeba move “seeds” of bacteria to a new location and plant them as a food source. In other words, they farm.

Ants grow fungus. Termites and some saltwater snails do ditto. Damselfish grow algae. But until now, nobody has identified any life form that “farms” bacteria, and nobody has identified any single-celled farmers, says Debra Brock, a graduate student in ecology and evolutionary biology at Rice University.

Adds Brock, whose report on farming amoeba appears in Nature tomorrow, “Certainly there has never been an amoeba that’s known to farm.”

Bring on the rebranding!

Working with the well-studied amoeba Dictyostelium discoideum (“dicty” to you and me) Brock noticed that the fruiting bodies — reproductive structures that distribute the amoeba in new habitat — seemed to contain bacteria. That was odd, Brock admits. “To get anybody to believe me, I had to prove that the little spots were bacteria, and not an infection.”

When she spotted the sorus (mass of spores) on growth medium, colonies of bacteria grew on some of the plates — showing that about one dicty in three transports bacteria. The bacteria didn’t seem to be a harmful infection, since amoebas with and without bacteria grew similarly, she says.

She fed the shape-shifters antibiotic to kill their bacterial cargo, but when the amoebas resumed eating bacteria, some bacteria showed up in the sorus. Since this only happened with amoebas that had originally carried bacteria, Brock concluded that this was normal, healthy behavior for those amoeba, although she’s can’t yet say whether the bacteria are inside or alongside the amoeba spores.

Photo: Scott Solomon

Fruiting bodies of the amoeba Dictyostelium discoideum contain bacteria and spores of amoebas. Each sorus is attached to a single slug, comprised of about 100,000 individual amoebas.

Wild about amoeba

The project began when Brock was studying wild amoeba rather than a strain that had been living in labs since the 1930s, and she noticed that some clones consistently carried bacteria.

Brock says dictys are “social amoeba” because “they have a structured society, and can exist in two states.” Individual amoebas in the soil eat bacteria, divide and eat some more. So long as edible bacteria are available, “they are perfectly happy to do this,” says Brock. “But if they use up all the food, they start talking to each other with chemical signals: ‘Wow! There’s not enough food!’ And then approximately 100,000 come together to form a slug.”

The slug serves as a truck to haul amoeba to new territory, Brock says. “During the multi-cellular part of the life cycle, they are starving, and they want to go somewhere else.”

The slug eventually shoots up a stalk containing amoeba spores, and among the farmers, bacteria. When the sorus opens, the bacteria can plant themselves as amoeba food.

Reminds us of Johnny Appleseed…

The Darwinian decision

Why does the same species of dicty use two survival strategies? Why do some farm while others don’t? “It’s a smart evolutionary strategy,” says Brock. “It’s bet-hedging. If you happen to land in a patch without bacteria, farmers have a great advantage because they bring their food with them, which allows them to grow and divide and bear a huge number of progeny while the poor non-farmers have nothing to eat.”

But while the farmers quit eating before they remove all bacteria from their old location, non-farmers can eat all those bacteria, so non-farmers do benefit if the new home already contains edible bacteria.

Apparently, both strategies work, because both have survived the evolutionary gauntlet. Brock is exploring whether a “farmer gene” causes some amoeba to hoard bacteria…

It’s enough to give a person a new respect for protozoans, which offers a firm basis for rebranding. “From quite a long time ago, we’ve thought we are so special,” says Brock, “but you can’t imagine the number of genes the amoeba has that are just like human genes. It’s scary; it takes you down a notch or two.”

– David J. Tenenbaum

In our world, boys buy bling to fetch females. In their world, fireflies use a bioluminescent belly — the abdominal embodiment of beetle-bling. Male and female fireflies use their flashes for mutual attraction; each of approximately 2,000 species uses a distinct signal to attract each other and avoid mating with other species.

Firefly Fun Fact

Fireflies are really beetles and a part of the taxonomic family commonly known as glowworms.

But why do the males in some firefly species flash in unison, and what does that say about the infinitesimal insect brain? Those questions weighed on the massive mammalian brain of neurophysiologist Andrew Moiseff, of the University of Connecticut. He used Photinus carolinus, a lightning bug from the Smoky Mountains, as a way to understand how fireflies process signals and distinguish “us” from “them.”

For many, fireflies are at the center happy childhood memories. For science, they could be a peephole into the brain.

Although the behavior he studied concerns mating, “We are looking at this from a different perspective,” says Moiseff. “What strategies do they need to allow the communication to take place? This is a very convenient system for understanding signal processing.”

A flash in the dark

Normally, local males of P. carolinus flash in unison, timed by an internal body clock. After a brief interval, nearby females flash the response call appropriate to females of the species. This unmistakable “come hither” allows the guys to find and mate with the glowing gal.

Most firefly males flash sporadically. Do P. carolinus guys get an evolutionary advantage from flashing all at once?

Definitely, according to a study published today in Science by Moiseff and Jonathan Copeland, of Georgia Southern University. They found that females respond dramatically better to unison flashing. Using a digital gadget to display phony flashes to a lady lightning bug, they found that her response rate fell from 82 percent after unison flashes to as low as 3 percent after sporadic flashes.

That would virtually guarantee that he would die a virgin — would be unfit for survival, in evolutionary terms.

Click here to view the embedded video.

Click here to view the embedded video.

P. carolinus forms a carnivorous larva that typically overwinters in the soil for a year before changing into a pupa and then an adult. The adult’s only job is to mate, so it lives only two to four weeks. Although adults don’t seem to eat, they do drink nectar.

After mating, momma flies deposit their larvae and kick the bucket.

In the Smokies, P. carolinus usually emerges in the first week of June, depending on the weather.

Unison flashing appears to increase the male firefly's chance at attracting a mate.

Advantage: unison!

We wondered if unison flashing could be confusing to the ladies, but Moiseff countered, “It depends on what you consider confusing. Yes, that does make it more difficult for her to chose a specific individual, but we don’t know if she chooses an individual.”

Changing the question to, “Can she see the pattern of the species she’s looking for?” illustrates the utility of unison illumination, Moiseff says. “Imagine, with a bunch of things flashing that may appear random, it may be difficult to detect that any one is the correct pattern, but if they are flashing simultaneously, the pattern will jump out at you.”

We can see why this would work for females, but why would greater competition for guys lead to more offspring, the test of evolutionary advantage? After all, most male sexual displays are designed to make one guy stand out in a crowd, not to make many guys look like a crowd. “It might be that if a male does not play along, he will not get chance to mate at all,” says Moiseff, hastening to note that he’s not tested this idea. “Under these conditions, you must cooperate and take your chance.”

Evolutionary enigma

The evolutionary question of unison flashing begs for an answer, but as neuroscientists, Moiseff and Copeland want to know about the mental equipment that the females need to recognize the signal of her own species. “She probably has to count, and to be able measure the time interval,” says Moiseff. “One major goal is to understand the brain circuits and sensory system that would allow the visual system to count, and detect a specific pattern from all the other things the visual system can see.”

The firefly brain contains just a few thousand neurons, and Moiseff notes that, using electrodes, it’s possible to measure their action, one by one.

One final note: The firefly offers something that the rat, fruitfly and nematode do not: a lovable research subject. “I’ve never met anyone who does not like them,” says Moiseff. “Even in places with no fireflies, there are firefly books and kid’s stories. Most people had the experience of catching them as a kid in summer. It’s such a pleasant childhood memory.”

And yes, as a kid, Moiseff did catch lightning bugs in a jar.

– David J. Tenenbaum

Bibliography

• Firefly Synchrony: A Behavioral Strategy to Minimize Visual Clutter, Andrew Moiseff and Jonathan Copeland, Science, 9 July 2010.
• More on Moiseff’s research.
• The Firefly Files.
• National Geographic’s firefly facts.
• The hidden cost of firefly flashes.
• The Bioluminescence Web Page.
• Weird animal courtship rituals.
• Short films about animal attraction by Isabella Rosellini.
• Another video of P. carolinus in action.
• Great Smokey Mountains and their synchronous fireflies.
• Great Smokey Mountain’s biodiversity inventory.

]]> http://whyfiles.org/2010/a-flash-in-the-night-sky/feed/ 0 http://whyfiles.org/2010/fish-phishing-attack-explained/ http://whyfiles.org/2010/fish-phishing-attack-explained/#comments Thu, 07 Jan 2010 21:24:26 +0000 svmedaristwf http://whyfiles.org/?p=3983 Fishy, fishy: Errant cleaning lady gets punished!

Many individuals engage in what social psychologists call “third-party punishment.” We may enforce social codes, even laws, related to marriage, sex, sexuality, vice and property. A classic example is a good Samaritan who ignores personal risk to chase a purse-snatcher.

Third-party punishment is so common that evolutionary psychologists suspect that it has genetic roots. Because punishment takes effort and can spark retaliation, it can only have evolved if it benefits the punisher: it can help the punisher reproduce (a direct benefit), or help the community survive (an indirect benefit).

Although the roots of human third-party punishment may have nothing to do with evolution, evolutionary psychologists often assume that its major benefit is indirect: I promote social stability by chasing a purse-snatcher. In stable society, I can have more children. Hence in evolutionary terms, chasing a purse-snatcher has indirect benefits.

Courtesy Gerry Allen

Colorful cleaners: A pair of blue-streaked wrasses ( Labroides dimidiatus ) clean Achanthurus mata.

But in a study published this week, researchers found that third-party punishment directly benefits the punisher, at least when said punisher is a “cleaner” fish. Cleaner fish eat parasites housed on larger fish, called “clients.” The relationship is classic symbiosis: the cleaner gets food, while the client stays healthy.

In the blue-streaked wrasse Labroides dimidiatus under study, males and females clean in pairs. Occasionally, a female cleaner switches from eating parasites to the more delectable mucus, a sticky goo that protects the client from infection.

(We sure swear to skirt slimy, sophomoric silliness and subsequently stick to the science.)

Your cheatin’ heart

Behavioral ecologists call this “cheating” because it breaks the symbiosis and harms the client.

Redouan Bshary of the University of Neuchatel in Switzerland studies the wrasse in the Red Sea. He says a client typically swims into a “cleaning station” for about 20 seconds, where a male and female wrasse eat parasites from its exterior. When the female cheats, the client tends to get annoyed and swim to another cleaning station – unless the male wrasse darts at the female to keep her in line. That’s third-party punishment.

Courtesy Richard Smith

A blue-streaked wrasse cleans a member of the genus Amblyglyphidodon

To test the situation in the lab, first author Nichola Raihani, a post-doctoral fellow at the London Zoological Society, smeared a Plexiglas plate with prawn meal or the less palatable fish flakes. When the females ate the prawn goop, the lab-keepers removed the plate and both fish confronted the sad sight of an empty menu.

When males responded aggressively to female cheating, the females were less likely to cheat again, reinforcing the notion that punishment would sustain the symbiosis and get him more food.

Is punishment beautiful?

Even though males were not directly harmed by the cheating, they directly benefited from the punishment, the authors wrote. “The establishment of self-serving third-party punishment in response to personal losses may be a key step toward third-party punishment without current involvement, as in humans.”

Scientists have observed punishment among other animals, says Katherine Cronin, a post-doctoral psychology research fellow who studies cooperation among monkeys at the University of Wisconsin-Madison. “Dominant rhesus monkeys might lash out at subordinates who didn’t properly alert them to food,” Cronin wrote us, “and female cowbirds (a species that lays eggs in other birds’ nests to be reared by hosts) may seek out and destroy the eggs of hosts who have previously destroyed cowbird eggs in a surprisingly mafia-like fashion.”

Nonetheless, Cronin says, “careful, experimental demonstration of punishment in animals has been rare and requires creative experimental designs like the one employed by Raihani and colleagues.” Cronin notes that cleaner fish are cooperative. “The strongest examples of punishment might not come from the most cognitively complex animals, but rather from the ones that rely most heavily on cooperation to survive.”

Photo: futureshape

The “good behavior” encouraged by this sign from the London (UK) police department may help the group and produce indirect benefits to the good-behaver. But in some cases, watching the behavior of others may also benefit the individual…

Sexual politics, fish-style

Exactly how does the male cleaner benefit from chasing misbehaving females? In most cases, we’d assume that keeping the food source (the client) around would constitute an evolutionary advantage because better-fed males can have more baby fishies, but we must remember that blue streaked wrasses are hermaphrodites. They begin reproducing as females, but females that grow large enough can turn into males.

Males can control this conversion, and avoid having another competitor for food, females and territory, by acting aggressively toward females, Bshary says. “If you remove the male, within two days, the female will show male behavior, and within a month, can release sperm that can fertilize eggs.”

And thus a male has an incentive to control the largest female in his harem, Bshary adds. “Typically the male tries to control her through aggression so she will not change sex. This is likely to be the main reason why the male responds aggressively to the female.”

What’s the human impact?

Whether the benefit is retaining food, a mate, or both, the study could shed light on puzzling human behaviors, says Raihani. “Until now, most studies on third party punishment have tended to assume it stems from a group-level benefit.”

A group-level evolutionary explanation for a crime-fighting good Samaritan would say that living in a crime-free society enables all people, including the Samaritan, to have more children. An individual-level explanation might suggest that the crime-fighting hero could gain social status, and therefore have a better choice of mates.

In the fish study, Raihani says, “We are trying to emphasize that you can get what looks like group-level behavior that evolves by individual selection.”

One final note, in case you thought the study is “just about fish.” The females are not the only fish who cheat, Raihani says. “Males cheat slightly more than females in this pair cleaning interaction, but females never punish males, because they are so much smaller.

So the males can have their cake and eat it too.”

Sound familiar?

David J. Tenenbaum

Bibliography

Punishers Benefit from Third-Party Punishment in Fish, Nichola J. Raihani, Alexandra S. Grutter and Redouan Bshary, Science, 8 Jan. 2010.

Related Why Files

How many fish in the sea?

Mammoth marine reserves: How useful?

Evolution: A fish story

Fishing: the power of profit

]]> http://whyfiles.org/2010/fish-phishing-attack-explained/feed/ 0 http://whyfiles.org/2009/animal-arms-race/ http://whyfiles.org/2009/animal-arms-race/#comments Thu, 16 Jul 2009 20:44:36 +0000 admin http://whyfiles.org/?p=2684 http://whyfiles.org/2009/animal-arms-race/feed/ 0 http://whyfiles.org/2009/after-the-chimp-attack/ http://whyfiles.org/2009/after-the-chimp-attack/#comments Fri, 06 Mar 2009 04:29:14 +0000 admin http://whyfiles.org/?p=1577 http://whyfiles.org/2009/after-the-chimp-attack/feed/ 0 http://whyfiles.org/2009/micro-eye-movements/ http://whyfiles.org/2009/micro-eye-movements/#comments Thu, 12 Feb 2009 21:11:25 +0000 admin http://whyfiles.org/?p=1547 You can’t hold your eyes completely still, but what is the purpose of those tiny movements? A new study could explain why we make them — and why we seldom notice them.

]]> http://whyfiles.org/2009/micro-eye-movements/feed/ 0