Brown Anoles and the Dead Man’s Hand

Posted on May 12, 2013 by

On a sunny August 2nd, 1876, the Union scout, lawman, and gunfighter Wild Bill Hickok was shot dead in a tavern in the town of Deadwood, in the Dakota Territory. He had followed the gold rush to the Black Hills of Dakota, hoping to strike it rich. But he spent most of his time drinking and playing poker in the frontier town’s saloons. On that day, he arrived late to the bar, and the only available seat at the poker table left his back to the door. On another day, he might have left, but this day, he chose to stay. That turned out to be a poor choice.

Wild Bill Hickok, looking dapper.

Wild Bill Hickok, looking dapper.

Hickok was a talented poker player. After a degenerative eye disease robbed him of his marksmanship, he relied on cards to make a living. He brought to the poker table all of the focus and cunning he had previously used as a scout and lawman. He could read people easily, and few men could bluff him for long. But all that attention came with a cost – his focus narrowed on the poker table, on watching the men with him, he failed to notice the door open behind him.

The last words he heard were “Damn you! Take that!”, before a bullet entered the back of his head and exited through his cheek. The buffalo hunter Jack McCall, enraged at being embarrassed by Hickok in a previous poker game, had sneaked up on the distracted Hickok and murdered him. On the floor lay the last hand Hickok was ever dealt: a pair of aces and a pair of eights, all black – since then known as the dead man’s hand.

The dead man's hand.

The dead man’s hand.

Animals live in groups for many reasons: to control territory or access to resources, to form alliances and, of course, they live in groups because that makes it easier to find a mate. But living in groups comes with costs – including the possibility that all of those wonderful friends surrounding you are making it more likely that you’re going to be eaten by a predator.

Like humans, animals have a limited capacity for attention. They can only pay attention to so many things at one time – trying to do too many things at once causes everything to suffer. (Study-after-study shows that multi-tasking, the Millenial’s favourite pastime, just results in doing five things poorly). For solitary animals, that means their attention is divided between two things: finding food, and avoiding predators. That’s pretty straightforward.

multitasking

But social animals have to divide their attention among more activities. They have to find food, look around for predators, look around to see if other individuals have located predators, and also pay attention to their needy friends that require constant attention. Heaven-forbid you’re a mother with babies to take care of too. A study published last week in the journal Ethology experimentally considered the cost of companions.

Jennifer Yee and her colleagues studied the brown anole, a ubiquitous lizard found in the Caribbean. Like all small critters, the brown anole is a favourite meal of just about everything bigger than it – but particularly snakes. Anoles rely on their keen eyesight to avoid becoming a snack – if the bushes rustle in a suspicious way they dart to safety. Yee tested the reaction time of anoles by harassing them with a rubber snake. She moved the snake to within a metre of an anole, and then recorded how much time it took for the anoles to notice. Solitary anoles noticed the snake quickly, and ran away. Good for them.

A brown anole, auditioning for a role in the Terminator movies

A brown anole, auditioning for a role in the Terminator movies. Credit: Neil Losin

 

But, anoles live at a fairly high population density, and are regularly distracted by other anoles. They may just be passing through, or they may be angling to steal your territory, or your mates, or your food. Regardless, they bear close watching. So the anoles all keep a  tense eye on one another – the same way Hickok might’ve been keeping a close eye on his fellow poker players. That sort of attention comes at a cost. Yee found that when anoles were distracted by the presence of other individuals, it took them twice as long to notice the presence of a predator – and the predator could be moved closer before the anole found it.

A green anole doing a poor job of paying attention.

A green anole doing a poor job of paying attention. Credit: USGS

That’s bad news for pre-occupied anoles. It was also bad news for Wild Bill Hickok. Distracted by the other poker players, he didn’t notice Jack McCall arriving at the bar behind him. Next time you’re at the bar, take the seat with your back to the wall.

Neil Griffin

Literature Cited

Yee J, et al. 2013. The Costs of Conspecifics: Are Social Distractions or Environmental Distractions More Salient? Ethology 119: 480-488.

Turner, T. 2001. Wild Bill Hickok: Deadwood City – End of Trail. Universal Publishers.

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Plant Picket Lines – The Fungal First Line of Defence

Posted on May 9, 2013 by

“All quiet along the Potomac”, they say,

Except now and then a stray picket

Is shot, as he walks on his beat, to and fro,

By a rifleman hid in the thicket

- ‘The Picket Guard’ (or, ‘All Quiet Along the Potomac’), Ethel Lynn Beers, 1861

Three wars in the span of 100 years defined the North American continent: the American Revolution, the War of 1812, and the American Civil War. These were violent, bloody, civil conflicts where families and friends fought against one another – and everyone knew someone on the other side. During these wars, the boundaries of an army’s encampment were patrolled by the picket line. Soldiers, alone or in pairs, stood watch on cold, dark nights in a scattered line around the camp, ready to alert the army if anyone attempted to cross the line. It was a dangerous and lonely job (although sometimes served well to highlight the ridiculousness of war – stories abound of Union and Confederate pickets set up within shouting distance of one another, jointly complaining about the quality of their sides rations). The job of the picket was essential. In the time before radar, before satellite imagery, and before night-vision, the pickets were an army’s best early warning system. They could shout, light fires, and ring bells if the picket line was breached. But what do you do if you’re under attack from an enemy, but you can’t move, or talk? Then you have the same problem that a plant does.

The Picket Guard, by NC Wyeth, 1922

The Picket Guard, by NC Wyeth, 1922

We don’t often think of plants as having behaviours, but they do. Witness the way flowers change their orientation to track the movement of the sun across the sky, or the way vines and lianas seek out light. Or, if you’re of a more sinister bent, the way Venus fly traps snap shut on their prey. These are all examples of behaviour – just because a plant can’t move, doesn’t mean it isn’t complex. And in some ways, because plants can’t move, their behaviour needs to be more complicated than that of animals.

If an animal meets a predator, it can run, or hide, or fight back. Plants are a little more limited in defence. They can’t run (duh), and their ability to hide is limited. Mostly, plants defend themselves against herbivore predators by fighting back: they grow spines or spikes, like a cactus or a rose; or they produce toxins in their leaves. The problem with producing toxins is that it costs a lot of energy – energy a plant would rather spend on creating flowers and growing bigger. So most plants try to minimize the amount of toxins in their leaves, until they know a predator is near – then they rapidly increase the number of toxins they exude, hoping to dissuade the herbivore from munching on them.

The merciless predator consumes its prey

The merciless predator consumes its prey

But if you’re not producing toxins until something is already eating you, you’ve left it a little bit late. Luckily, plants have their own sort of early warning system – a complicated, underground network of symbiotic fungus that warns them when neighbouring plants come under attack.

Like an iceberg or that quiet artsy kid in your class, much of the life of a plant is carried out beneath the surface, in the root system. Plants extract nutrients and moisture from the soil, and use those nutrients, combined with carbohydrates from photosynthesis, for their growth. But, plants are not very efficient. They’re actually quite poor when it comes to squeezing nutrients from dirt, so they rely on a helper. Most plant roots are covered in mycorrhizal fungi – long, stringy threads of fungus that work together with the roots. The fungi increase the surface area of the roots, allowing for more nutrient uptake, and in return the plant supplies the fungus with carbohydrates. Everybody wins. But the fungus provides another benefit.

Mycorrhizal fungi connecting the root systems of three plants. Credit: Garden of Eaden

Mycorrhizal fungi connecting the root systems of three plants. Credit: Garden of Eaden

The mycorrhizal fungi spread out over a much larger area than the plants roots do, and often mingle with the fungus connected to other plants. This fungus is the plants picket line. When one plant along the line is attacked by an herbivore, the fungus detects the attack, and passes a message to all of the other plants: “We’re under attack, you might be next, begin producing toxins.” The surrounding plants then have time to prepare their defences before the predators reach them. Without the fungus providing an early warning system, no plant in the area would have the time to raise its defences before being eaten. The first plant may die, but the picket line ensures that the rest of the plants will be prepared.

But the picket line isn’t always so benevolent. Mycorrhizal fungi are a bit promiscuous – they don’t favour specific plant species, and instead will attach to the roots of most plants. This creates a massive, underground network of interconnected plant species. In the event of attacks, this is good. But some plants have evolved to take advantage of this network by sending false signals down the line – messages that stunt the growth of other plants. They’re the cheaters, who send false codes down the picket lines in order to deceive the species they’re competing with.

One plant guilty of this deception may be lurking in your garden right now – the common marigold. It’s always the pretty ones.

A manipulative double-agent. Credit: artbyprem.com

A manipulative double-agent. Credit: artbyprem.com

Neil Griffin

Literature Cited

Babikova et al. 2013. Underground signals carried through common mycelial networks warn neighbouring plants of aphid attack. Ecology Letters doi: 10.1111/ele.12115

Barto et al. 2011. The fungal fast lane: common mycorrhizal networks extend bioactive zones of allelochemicals in soils. PLoS ONE 6: e27195.

Trewavas A. 2009. What is plant behaviour? Plant, Cell & Environment 6: 606-616.

Posted in Ecology, Science | Tagged , , , , , , , , , , , , | Leave a comment

Earth Perfume and the Scent of Rain

Posted on April 28, 2013 by

Calgary is generally not a bad place to live. It was recently ranked #5 on a list of the world’s best cities to live in (a fact which bemuses most Calgarians -  the general consensus is that the judges must have only visited in the summer). One of the climatological quirks that make Calgary appealing is its sunshine. It’s the sunniest city in Canada, and one of the sunniest in North America. Sure, some of these sunny days happen to coincide with −40 temperatures, but where else in the world is it so easy to get sunburn and frostbite at the same time?

Winter in Calgary is a welcoming place. Credit: Glenn Little

Winter in Calgary is a welcoming time of year. Credit: Glenn Little

The downside of Calgary’s weather, for some people, is the absence of rain. Our rain tends to come in dramatic, mid-summer thunderstorms that move between rain and hail for short periods of time, and then disappear (often having destroyed a few cars, knocked over a few deck umbrellas, and shredded a few gardens). There is no relaxing pitter-patter of a gentle late-night drizzle, no afternoon showers to ease the heat of the day. It’s Biblical inundation or nothing. Which is too bad, because it means we don’t get to experience petrichor – the scent after rain.

I bet you didn’t know that earthy, fresh smell had a name, but it does. Petrichor is the name given to the characteristic scent produced by arid soil after a rainstorm. It means “essence of the soil”,  but let’s be poetic, and call it the essence of the Earth. Two geologists named the scent in the 1960s, in a paper published in Nature, but it has many other names too. In Lucknow, India the scent is collected from clay-disks inundated with rain during the monsoon season. It is mixed with sandalwood oil and sold in vials as matti ka attar – earth perfume. In the parched red clay deserts of Western Australia, the Anangu people call it panti wiru, simply meaning ‘good smell’. It is the harbinger for a wave of greenness and fresh vegetative growth to overtake the desert - signalling a time of plenty. Panti wiru is associated with youth, health, fecundity, and new beginnings.

Most desert plants wait in eager anticipation for any rain. The smallest rainfall can trigger an explosion in growth almost over night. This picture is from Death Valley, California.

Most desert plants wait in eager anticipation for any rain. The smallest rainfall can trigger an explosion in growth almost over night. This picture is from Death Valley, California.

The odour comes from actinomycetes (a group of bacterium that we met earlier). Actinomycetes are members of the actinobacteria – a tremendously large phylum of bacteria, which are among the most common organisms on Earth. Actinobacteria are found everywhere: in the ocean, in lakes and streams, and in the soil. They are responsible for breaking down dead and decaying plant and animal life, recycling nutrients into an ecosystem so they can be used to fund new growth. Actinobacteria are also the source of the antibiotic actinomycin – which sort-of morally balances out the fact that they are also responsible for tuberculosis, leprosy, and diphtheria.

When wet, actinomycetes exude a number of chemical compounds, including one responsible for the smell of rain – geosmin. Geosmin was identified in 1965 (clearly the 1960s were the best time for “scent of rain research”), and has since been isolated from many different species of bacteria – but researchers have yet to determine its purpose (if it even has one). But that’s not to say other species haven’t learned to take advantage of its distinctive smell. The glass eel (Anguilla anguilla) spawns in the ocean, but must navigate to fresh-water estuaries to grow and develop (as the ocean is a frightening and unfriendly place for a little fish, but given the frequency with which glass eels are eaten, freshwater may not be that much safer of an option). To do this, they use their nose (technically they’re called nares, but the principal is similar to smelling).

A glass eel. When it reachers freshwater, the food it ingests contain pigments which give it colour - but as a juvenile, it is translucent.

A glass eel. When it reachers freshwater, the food it ingests contain pigments which give it colour – but as a juvenile, it is translucent.

Geosmin is produced by actinomycetes on the banks of rivers and flushed downstream. Eventually, dilute amounts of the scent makes its way into estuaries and deltas, before being pushed out to sea. Glass eels detect the trace amounts of geosmin, and follow the scent gradient until they find the river, then migrate upstream to grow safely, until they are big enough to move back to the ocean and have babies of their own. The amount of geosmin in freshwater is a concern for fishermen too. Too much geosmin in the water creates fish that have a musty, off-flavour that many people find unappealing. But too little geosmin in the water, and fish can be flavourless. It’s less of a problem in wild-caught fish, but aquaculture systems that use recycled water can have a build-up of geosmin that cause fish to taste like a mudpie. Basically, bacterial sweat is determining the flavour of your salmon. Something to keep in mind next time you go fishing.

montana-fly-fishing5 - dixonadventures

Neil Griffin

Literature Cited

Bear IJ and RG Thomas. 1964. Nature of argillaceous odour. Nature 201: 933-935.

Farmer LJ, JM McConnell and DJ Kilpatrick. 2000. Sensory characteristics of farmed and wild Atlantic salmon.  Aquaculture 187: 105-125.

Gerber NN and HA Lechevalier. 1965. Geosmin, an earthy-smelling substance isolated from actinomycetes. Appl. Microbiol. 13: 935-938.

Tosi L and C Sola. 2010. Role of geosmin, a typical inland water odour, in guiding glass eel, Anguilla anguilla (L.) migration. Ethology 95: 177-185.

Young D. 2005. The smell of greeness: cultural synaesthesia in the Western Desert. Etnofoor 18: 61-77.

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Nature’s Top Gardeners and their Homemade Ant-ibiotics

Posted on April 25, 2013 by

It’s Spring (at least according to the calendar), which means the gardeners are taking out their gloves and sharpening their shears. I’ll confess, I don’t have much of a green thumb. I once insisted on buying flowers for my apartment balcony. I tended them with love and care for a few days, but then went on vacation. When I returned, they were dry, straw-like husks, and for weeks I lived in fear of summons from the Gardener’s International Court of Justice. But for many, gardening is a way of life, not just a passing infatuation. It’s an ancient hobby, but humans don’t claim to being the inventors of gardening, that right belongs to the leaf-cutter ants. 

A blue ribbon gardener. Your granny can't lift 20 times her own bodyweight above her head. Credit: Nat Geo

A blue ribbon gardener. Your granny can’t lift 20 times her own bodyweight above her head. Credit: Nat Geo

 Leaf-cutter ants are the undisputed champion gardeners of the animal kingdom (sorry, Calgary Horticultural Society, you’re a close second). There are 47 species of leaf-cutter ant, divided between two genera (Atta and Acromyrmex). They live in forests of Central and South America, in massive colonies spanning over 1 ha of ground, and containing up to eight million ants. Their biannual gardening conventions are, as you can imagine, raucous affairs. Leaf-cutters gather leaves from the forest, and cart them back to underground nests, where they chew the leaves into a pulpy mush, and then use them as a base to grow fungus gardens on. The result is a symbiotic relationship. The fungus grows in a sheltered environment, safe from predators, and with its every need catered to. The ants gain a ready source of nutrition for their growing colony by eating small amounts of the fungus. 

 Like all gardeners, the ants are neurotic and fussy about their plants. They  flit from area to area, pruning and deadheading fungal hyphae, and licking the fungi to keep it growing. When experimentally excluded from the garden, they grow agitated, and immediately rush back to the neglected area (perhaps also throwing a disdainful glance over their shoulder, aimed at whatever prevents them from being in the garden all hours of the day and night). The ants are dedicated and capable horticulturalists, but like all gardeners they face the ever-present problem of pests. 

So maybe it looks a little different from your garden, it's still impressive. Credit: Jarrod J Scott

So maybe it looks a little different from your garden, it’s still impressive. Credit: Jarrod J Scott

 For leaf-cutter ants, the major pest in their fungus gardens is a parasitic fungi called Escovopsis (which sounds a little like a sinister multinational company in a spy thriller). Escovopsis devastates fungus gardens. Like the Greeks hiding in the Trojan Horse, spores of Escopvopsis hide on the cuticle (the waxy, water-proof outer layer) of normally harmless small invertebrates that wander with relative impunity throughout the leaf-cutter’s colony. The spores detach in the fungus garden, and then parasitize the ant’s garden, sucking the nutrients from the good fungus to fuel its own growth. Left to its own devices, the parasitic fungus causes the rapid failure of the gardens (and takes with it any chance of first place in the gardening competitions). 

 Luckily, the leaf-cutter ants have a pesticide – and they don’t even have to brave the gardening centre on a Saturday morning to buy it (seriously, is there a more frightening place on Earth?). On the underside of the cuticle of some gardening ants, there are fuzzy white flecks that look like a skin condition. The flecks are tiny colonies of actinomycetes, a type of bacteria formed from long, branching filaments. They look a bit like a pile of gummy worms. The particular bacterium carried by the gardening ants has antibiotic capabilities – it exudes chemicals that kill the parasitic Escovopsis. The ants carry, on their bodies, the only pesticide they need to keep their gardens clean and healthy. 

The antibiotic bacterium on the underside of leaf-cutter ants. Credit: Currie et al 2006

The antibiotic bacterium on the underside of leaf-cutter ants. Credit: Currie et al 2006

 Gardening is often an inter-generational hobby: mom or dad gardens, and the kids play in the mud – and the ants are no exception. The antibiotic bacterium is transmitted between parents and offspring, and then carried to a new nest. When a colony dies, and new, would-be queens leave the nest, they carry a small colony of the bacteria in a cavity on their cuticle – like a college kid going off to school with a collection of mom’s best recipes. When the queens first clutch of eggs hatch, the new-born workers get a good inoculation of the bacterium before they start work on a new garden. 

 Leaf-cutter ants are considered pests themselves by farmers, but they provide a valuable service to rainforest ecosystems. The waste they produce is rich fertilizer for poor rainforest soil, and their nests, once abandoned, become hotspots of new growth. And they are perhaps the most complex example of cooperation and symbiosis in nature. Three species – the ants, the good fungus, and the bacteria – entwined in a complex evolutionary dance, where none can survive without the continued assistance of the other two. We’d do well to learn some lessons from their cooperation. 

Cooperation! Credit: Richard Seaman

Cooperation! Credit: Richard Seaman

 Neil Griffin

 Literature Cited

Bass M, and JM Cherrett. 1994. The role of leaf-cutting ant workers (Hymenoptera: Formicidae) in fungus garden maintenance. Ecological Entomology 19: 215-220. 

Currie CR, JA Scott, RC Summerbell and D Malloch. 1999. Fungus-growing ants use antibiotic-producing bacteria to control garden parasites. Nature 398: 701-704. 

Lugo et al. 1973. The impact of the leaf-cutter ant Atta colombica on the energy flow of a tropical west forest. Ecology 54: 1292-1301. 

Poulsen M, ANM Bot, CR Currie, MG Nielsen and JJ Boomsma. 2003. Within-colony transmission and the cost of a mutualistic bacterium in the leaf-cutting ant Acromyrmex octospinosus. Functional Ecology 17: 260-269. 

Reynolds, HT and CR Currie. 2004. Pathogenicity of Escovopsis weberi: The parasite of attine ant-microbe symbiosis directly consumes the ant-cultivated fungus. Mycologia 96: 955-959. 

Posted in Ecology, Evolution, Science | Tagged , , , , , , , , , , , , , , , , , , | 2 Comments

The Mystery of Asparagus Pee

Posted on April 21, 2013 by

Benjamin Franklin was a great many things: statesman, journalist, writer, Europhile, teetotaler and womanizer. He was also an astute observer of the human condition, and one of those conditions he observed so astutely was the after-dinner consequences of eating asparagus: “a few stems of asparagus shall give our urine a disagreeable odor.” Now perhaps this was political metaphor – a few small stems of England contained in the greater body of the nascent American Republic would give the whole thing a foul odor, therefore America had to cleave itself from its British ancestors.

But more likely he was just saying, “pee smells funny after eating asparagus.”

Proust, on the other hand, wrote that asparagus succeeded at " transforming my humble chamberpot into a bower of aromatic perfume."

Proust, on the other hand, wrote that asparagus succeeded at “transforming my humble chamberpot into a bower of aromatic perfume.”

Now some of you out there (between 40% and 80% of you, depending on the studies) are going to have no idea what I’m talking about. This as because, as SC Mitchell wrote in his review of asparagus-scented urine: “there is no reason why these two opposing factions [those who smell it and those who don’t] should converse on the subject.” But, for the curious, Mitchell assures us that “a brief discourse with one’s colleagues will confirm such differences and verify [the] state of affairs.⁠1” For those who don’t know, the state of affairs is that some varying proportion of the population produce urine that smells like rotten cabbage after they eat asparagus, and the rest of the world is none the wiser.

For many years (this has been studied, regularly, since at least the early 70’s) researchers assumed that the odor production was a metabolic hiccup that occurred during the breakdown of asparagus. Some people’s digestive system functioned slightly differently than the non-stinkers, and produced foul smelling chemical metabolites that are drained away when you pee. A great scavenger hunt ensued, as bored chemists sought to find the mystery chemical. Over 20 chemicals have since been proposed. They vary in structure and complexity, but all contain sulphur – the cause of the rotten cabbage smell.

asparaguspee

For the sake of my journalistic integrity, I guess I should mention that I’m reporting the smell largely on hearsay. I can’t smell it. And I don’t think I produce it (nobody wants to stand in the bathroom while I pee and then tell me). But it’s complicated. Is the production of the asparagus pee linked to the detection of it? Can a person produce it, but not smell it? Or smell the asparagus pee produced by other people, without producing it themselves?

Can he who dealt it, smell it?

But thanks to the valiant (and strange) efforts of Dr Marcia Levin Pelchat and her colleagues at Monell Chemical Senses Center and the University of Florida, we have answers. Pelchat and co. wanted to investigate the production and detection of asparagus pee (I don’t know why). They noticed that many previous studies were poorly controlled. The standard testing procedure for determining whether someone can detect the bouquet du asparagus was to make them sniff jars of urine, and answer the question, “does one of these smell funny?”

Pelchat pointed out, rightly, that urine in general smells funny, and this test likely gets a lot of false positives by chance. So she set out to be a little more rigorous. First, she recruited volunteers using what I can only imagine was a fantastic job posting: “Researchers seeking urine-sniffers”, “Science needs YOU to sniff a stranger’s pee”.  The volunteers then followed a fairly basic procedure. They spent an asparagus-free 24 hours, then came into the lab and peed in a cup. A few days later, they came to the lab and were fed asparagus and water. Two hours later, they peed in another cup. That procedure was repeated again, but the volunteers ate bread instead of asparagus, to create a control sample.

Then, the volunteers probably began to regret their participation. Throughout the week, they were asked to come into the lab, and sat in room. Placed in front of them – two unlabeled jars of urine (sometimes their own, sometimes someone else’s). They were then asked to sniff both, and point out the one that contained asparagus. Pelchat records that some volunteers were “unable to do this” – not unable to detect the asparagus, but unable to smell another person’s pee (presumably because they wanted to throw up), but most of the volunteers were game. The researchers also collected DNA samples from each volunteer.

This is not a jar of pee. Credit: stirandstrain.com

This is not a jar of pee. Credit: stirandstrain.com

The results have the pungent odor of well-controlled science. Almost all of the participants produced an asparagus odor detectable by the other volunteers. But, a few of the volunteers couldn’t reliably smell the asparagus pee. The DNA swabs hold the answer why. The team were interested in a genetic region on chromosome 1 which contains olfactory genes – genes related to the sense of smell. In particular, they found that a single nucleotide polymorphism (SNP) between the genes OR2M7 and OR14C36 explains the variation in the ability to detect – but not produce – asparagus pee.

An SNP is a single letter change in the genetic code – like changing CAT to HAT. It’s a comparatively small change, but can have major consequences on the function of a gene. In this case, a single letter change makes individuals unable to detect asparagus pee. The medical name for this condition is “specific anosmia” – the inability to smell a particular odor. But those individuals can still produce asparagus pee.

He who dealt it, can’t always smell it.

asp2

Neil Griffin

1 I encourage you all to bring this up tomorrow during your lunch break

Literature Cited

Mitchell SC. 2001. Food idiosyncrasies: beetroot and asparagus. Drug Metabolism and Disposition 29: 539-543.

Pelchat ML, Bykowski C, Duke FF and DR Reed. 2011. Excretion and Perception of a Charactersitic Odor in Urine after Asparagus Ingestion: a Psychophysical and Genetic Study. Chem. Senses 36: 9-17.

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Why Beavers Shouldn’t Binge Drink

Posted on April 18, 2013 by

There are countless reasons why beavers shouldn’t binge drink. They rarely live over the age of 20, meaning in most places in North America they’re below the legal drinking age for their entire life. Binge drinking is associated with violence and aggressive behaviour – and baby beavers are too cute to subject to that. Plus could you imagine nursing a hang-over and trying to build a beaver dam at the same time? Not gonna happen. But the number one reason why beavers shouldn’t binge drink is that they would probably die – because unlike the undergraduates all over the University of Calgary campus this week, beavers can’t throw up.

Binge drinking leads to baby beaver broken homes.

Binge drinking leads to baby beaver broken homes.

Vomiting while drinking is the body’s way of saying, “hey buddy, please stop poisoning me”. Barfing is an adaptive strategy – an automatic rejection hotline that lets the brain and stomach override your dumb decision to eat or drink whatever you should’ve known better about. It’s a complicated maneuver, equal parts elegant and disgusting. The brain triggers a synchronized dance of muscle contractions that stimulate the stomach, causing pressure build-up until, a little bit like a geyser, “expulsion occurs.” But beavers can’t do it. Neither can Norway rats, house mice, voles, or mountain beavers (which, I was disappointed to discover, is not a regular beaver who wears plaid and an unkempt beard). Neither, as it turns out, can guinea pigs (which makes them lousy guinea pigs)⁠1

Apparently, however, guinea pigs do make good spies.

Apparently, however, guinea pigs do make good spies.

Researchers (and pest control folk) have known for a long-time that some rodents can’t vomit. Rat poison is effective because the rats can’t throw it up. But it was only this week that scientists discovered why rodents can’t vomit. In a paper published in PLoS ONE, Dr Charles Horn and co. at the University of Pittsburgh Cancer Institute answered all the questions you didn’t know you had about rodent barfing. Horn and colleagues gathered seven species of rodent (and a few rodents) and tested their barfability by injecting them with emetics (which sounds like something out of Scientology, but is really just code for “chemicals that make you throw-up”). They then put the rodents in a mirrored study chamber, and filmed their behaviour to look for evidence of vomiting.

On second thought, "dianetics" and "emetics" probably do induce the same reaction in people. Don't sue me, Church of Scientology.

On second thought, “dianetics” and “emetics” probably do induce the same reaction in people.

The rodents moved around more (possibly because they were distressed), and drooled sometimes, but didn’t throw-up (though maybe they were just being polite and didn’t want to puke on camera). After establishing the non-barfability of the animals, the scientists investigated brain activity and digestive anatomy, to see why they couldn’t puke. Vomiting, as mentioned above, relies on a signal from the brain – like pressing the eject button on a fighter jet. But when the researchers tickled this area of the brain in rodents (tickled being a polite euphemism for “doing strange, Frankenstein-like things”), the signal didn’t get sent. Someone forgot to check the wiring on the rat’s eject button. But even if the signal were sent, the rodents wouldn’t be able to follow through.

The second part of the two-part vomit process involves contracting stomach muscles to build pressure – like squeezing a bagpipe, if instead of air, the bagpipe was filled with partially digest haggis. Rodent stomachs, though, are too weak. They can’t build enough pressure to force stomach contents up an elongated esophagus. Rodent stomachs also “lack an obvious funnel-like structure”. They just weren’t built for barfing. The inability to vomit makes them not very useful for lab work on motion sickness (which is good for them), but also means they need to be careful what they eat (and drink). And that’s why beavers shouldn’t binge drink.

Take it easy buddy.

Take it easy buddy.

Congratulations, Dr Horn, on what I’m sure will be your forthcoming IgNobel Prize.

Neil Griffin

1 NASA has subjected all sorts of animals to motion sickness testing in an effort to understand space sickness in humans. For a long time, as recounted in Mary Roach’s Packing for Mars, NASA wondered if guinea pigs held the secret to discomfort-free space travel because they didn’t appear to get space-sick. But it turns out they just can’t vomit, and NASA has been looking for answers in the wrong rodent.

Literature Cited

Horn et al. 2013. Why Can’t Rodents Vomit? A Comparative Behavioral, Anatomical, and Physiological Study. PLoS ONE 

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A Study in Pink: Why Flamingos Wear Make-Up

Posted on April 14, 2013 by

Most animals are shallow (it may be a little unfair to make such a broad generalization, but they can’t read, so I’m probably off the hook for libel). A great personality doesn’t count for much in the animal kingdom. You can be the most kind, the most thoughtful widowbird on the savannah – but if your tail’s too short, you’re out of luck. It’s all about looks. Luckily, if you haven’t been blessed with an abundance of natural beauty, there’s always the possibility of faking it – and one bird species is an expert at that: the flamingo.

Flamingos are familiar to most people from zoos, tacky watercolour paintings at dentist’s offices, and Disney’s Fantasia. There are six species of flamingo (and one run-down hotel in Las Vegas), and they’re found naturally on every continent except Australia and Antarctica. They’re probably found in zoos in Australia, but Antarctica doesn’t have any zoos (for obvious reasons), and so it remains flamingo-free.

A Chilean flamingo, looking just thrilled about life. Credit: Neil Griffin

A Chilean flamingo, looking just thrilled about life. Credit: Neil Griffin

Flamingos are best known for two things: standing on one leg, and being pink. They probably stand on one-leg to reduce heat-loss when standing in bodies of water for extended periods of time. However, a second (and so-far unexplored) possibility is that flamingos are involved in a Survivor-esque game, and the flamingo to place both its feet down first is sacrificed to a hungry baboon. One question that has yet to be answered (perhaps the most important question in all of science) is whether or not flamingos favour a certain leg – are their left and right-legged flamingos? If you have access to a large flamingo colony and too much free time, you could have a scientific publication at your fingertips.

They start at a young age.

They start at a young age.

The second well-known Flamingo Fact is that they are pink. But why? Well, first, they’re not always that colour. Flamingos range in colour from a sickly white to a bright red. They’re born a sort-of dull grey colour, and change as they age. The colour of their feathers is determined by their diet. Flamingos eat blue-green algae (which, confusingly technically isn’t algae).  Blue-green algae are actually bacteria that obtain energy via photosynthesis – like microscopic plants. The bacteria are found just about everywhere on Earth, and make a tasty meal (for flamingos and humans: edible blue-green algae are pretty good for you. Just don’t accidentally eat the toxic kind).

Third flamingo fact - they are all law abiding. Credit: Neil Griffin

Third flamingo fact – they are all law abiding. Even if the sign is mispelled. Credit: Neil Griffin

Blue-green algae photosynthesize using chloroplasts – organelles within plant cells that turn energy from the sun into chemical energy (in an equation that has for decades haunted the dreams of undergraduate science students). Chloroplasts capture the light used for photosynthesizing in carotenoids. Carotenoids are pigments that absorb specific wavelengths of light – kind-of like a solar panel. Chloroplasts can then use the energy stored in the carotenoids for photosynthesis. Carotenoids are used by humans and other animals as anti-oxidants, and in the maintenance of the eye. But we can’t get synthesize them ourselves (life would be much easier if we could), so we have to eat them.

But animals only need so many carotenoids. Extra carotenoids are metabolized slowly by the body, and expelled, but they can do some funny things in the mean time. In the case of flamingos, consuming more blue-green algae than their body can metabolize causes the reddish tint of their feathers. Carotenoids (which absorb blue light, and reflect red light – and therefore appear red to us) ooze into the feathers, and give flamingos their characteristic colour. And female flamingos like it.

If humans eat too many carrots, the orange-coloured carotenoids may seep into their skin, giving them a temporary orangish glow, known scientifically as "carotenemia" and otherwise as "Oompa Loompa Syndrome".

If humans eat too many carrots, the orange-coloured carotenoids may seep into their skin, giving them a temporary orangish glow, known scientifically as “carotenemia” and otherwise as “Oompa Loompa Syndrome”.

Female flamingos admire a man who is confident enough to wear pink. Having a pink or reddish tinge to your feathers as a male flaming, indicates that you are healthy – you have eaten so much blue-green algae that your body doesn’t even know what to do with it anymore. On the other hand, white or pale flamingos have not been feeding as well, and may be in poorer body condition. Females prefer to mate with pink or red males.

This is a very attractive flamingo.

This is a very attractive flamingo.

Which poses a problem for the male whose diet hasn’t been great. Luckily, he can fake it. Flamingos, like most birds (and celebrities) spend a lot of time preening. Preening is important for maintaining feather cleanliness and health, but flamingos use it for another purpose. On the base of the tail, birds have an uropygial gland. This is a gland that secretes preening oil – the oil can be anti-parasitic, or waterproofing, or just smell nice (to birds, it’s almost always unpleasant to humans). In flamingos, the oil is partially cosmetic.

This is not.

This is not.

During times of the year when flamingos aggregate into large flocks (and a males chances of getting lucky increase), the preening oil begins to contain carotenoids. The sneaky males use the carotenoid-enhanced oil as make-up, smearing it across their feathers to make them appear redder. When no one is around (the equivalent of home alone on a Sunday morning), they can’t be bothered, and their feathers stay a normal pale colour. But when they’re going out on the town, they smear themselves with make-up until they look like the prettiest flamingo around. Like I said, animals are shallow.

Neil Griffin

Edit: On reading this, my Mom just informed me that when I was a baby I had carotenemia because “the only vegetable [I] would eat were carrots and squash. Anything green usually ended up on the floor, the walls, and [my] hair, which was not an attractive look.”

Thanks Mom.

Literature Cited

Amat et al. 2011. Greater flamingos (Phoenicopterus roseus) use uropygial secretions as make-up. Behavioral Ecology and Sociobiology 65: 665-673.

Anderson, MJ and SA Williams. 2009. Why do flamingos stand on one leg? Zoo Biology 29: 365-374.

Hill, GE. 1996. Redness as a measure of the production cost of ornamental coloration. Ethology, Ecology and Evolution. 8: 157-175.

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Shouting “Fire” in a Crowded Theatre: Meerkats and the Fork-Tailed Drongo

Posted on April 11, 2013 by

Meerkats have a difficult life, hakuna matata aside. They live in harsh desert environments, where both droughts and flash floods are common and daily temperatures soar to 50°C. Food (insects and grubs) can be difficult to come by, and even more difficult to eat – catching a live scorpion without getting stung is not an easy skill to learn. To make matters worse, everything likes to eat meerkats. Luckily, meerkats live in large colonies that provide some defence from predators. That defence comes in the form of alarm calls.

Some joke about warthogs probably goes here.

Some joke about warthogs probably goes here.

The characteristic posture of a meerkat is standing bipedally, on its hind legs, looking around. This is a vigilance posture.The meerkats are looking for predators: birds of prey in the air, and snakes and foxes along the ground. If the look-out spots a predator it gives a shrill alarm call, alerting all of the nearby meerkats to abandon their feeding and head for shelter. The look-out is not an ideal position to be in. You don’t get to eat, and while you do spot predators first, they may also spot you (although whether being a look-out is riskier than feeding is still debated, by the people who debate those sorts of things). So meerkats rotate (perhaps down in their burrow is a little meerkat scheduling sheet) – after an individual stuffs its face until it’s full, it takes a little break and acts as look-out, until it’s relieved by a satiated relative. This system of look-outs and alarm calls lets meerkats maximize the time they spend feeding, which is important in a harsh environment.

A meerkat keeping watch. Credit: Hannes Lochner

A meerkat keeping watch. Credit: Hannes Lochner

But one species of bird has learned to exploit the system.

The fork-tailed drongo is a small, solitary bird that mostly eats insects and small lizards. But it’s also a little bit of thief, “kleptoparasitizing” other species – stealing the resources of other animals. Other famous kleptoparasites include gulls, jackals, and Wall Street bankers. The fork-tailed drongo’s favourite target is the meerkat, because meerkats dig up large, juicy bugs that are otherwise inaccessible to the birds. Meerkat’s defend their food ferociously, but they’re not immune to a little trickery.

The conniving fork-tailed drongo. Credit: Robert Scott

The conniving fork-tailed drongo. Credit: Roger Scott

Fork-tailed drongos are vocal acrobats, capable of mimicking the calls of a number of other species, including the meerkat. When the drongo sees a meerkat with food, it will land in a tree near the meerkat and give an alarm call. Not just any alarm call – it mimics the call of the meerkat. Frightened and alerted, the meerkat drops its food and heads for cover, and the drongo steals the abandoned food. Using a careful series of playback experiments and observation, Tim Flower from the University of Cambridge established that meerkats believe the drongos false-alarms, but also that drongos sometimes tell the truth: about 50% of their alarm calls are given after detecting a real predator.

If the fork-tailed drongo always lied, meerkats could probably learn to differentiate between their own calls and the mimicked calls of the drongo – acoustically they’re very similar, but not identical. Like the villagers in “the boy who cried wolf”, the meerkats would eventually come to just ignore the drongo calls, and the drongo would get no free meals. But because the bird is telling the truth about half the time, there is no selection on the meerkats for telling the difference between fake and real alarms. Any meerkat who tries to call the drongo’s bluff is playing a dangerous game. If the meerkat doesn’t respond to a real alarm, it’s likely to die – losing food by responding to a false alarm is not as bad as losing your life by failing to respond to a real alarm. Rather than play the odds, meerkats always drop what they’re doing and run for cover. The mixture of real and fake calls keeps meerkats on their toes, and lets the drongo continue it’s thieving ways.

A meerkat and a drongo. Credit: Tim Flower

A meerkat and a drongo. Credit: Tim Flower

The drongo’s aren’t tiny criminal masterminds. They probably aren’t aware of the way they actively manipulate the minds of the poor little meerkats. Instead, crime runs in the family – juvenile drongo’s accompany their parents and learn how to steal through trial-and-error. Kleptoparasites are made, not born. Maybe there’s hope for Wall Street (but probably not).

Neil Griffin

Literature Cited

Flower, Tim. 2011. Fork-tailed drongos use deceptive mimicked alarm calls to steal food. Proc. R. Soc. B 278.

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Two Dads Are Better Than None: Marmosets and the Real Modern Family

Posted on April 7, 2013 by

Children (I’m led to believe) exist somewhere in between “miracle of life” and “pain in the ass” (depending on their age, cuteness, and propensity for rolling their eyes). But at least they stay small and controllable for a while. Spare a thought for the marmoset.

Marmosets are a group of 22 species of Central and South America monkeys. They’re small, furry, and rather twitchy – like kittens on Speed. Generously, their brains are described as “primitive”. Usually when a scientist describes something as primitive they mean that evolutionarily its very old – but in the case of marmosets we can say they’re very old, but also not very smart. I once watched one get outsmarted by a grasshopper – an insect not notorious for being an intellectual giant.

Despite the noble appearance, rest assured, he is not thinking about anything. (Also this is a tamarin, not a marmoset. But they're cousins). Credit: Neil Griffin

Despite the noble appearance, rest assured, he is not thinking about anything. (Also this is a tamarin, not a marmoset. But they’re cousins). Credit: Neil Griffin

But their brain size isn’t what makes marmosets unique – lots of animals aren’t very bright. Marmosets are interesting for their reproduction. Like good Irish Catholics, marmosets never have just one kid. Marmoset mothers always give birth to fraternal twins, and occasionally to triplets. Twinning is not uncommon the animal kingdom. Human twins occur in approximately 33 out of ever 1000 births, and twinning also happens in deer, cats, sheep, ferrets, giant panda and cattle. But marmosets are one of the only animals where twins are the norm. As if having two or three kids wasn’t enough work to begin with, marmoset babies are gigantic. At birth, a marmoset baby weighs about 1/3 what the mother weighs. Imagine giving birth to a 40 lb baby. Now imagine giving birth to two of them.

A marmoset male with two babies clinging on for dear life. Credit: Nick Gordon

A marmoset male with two babies clinging on for dear life. Credit: Nick Gordon

Trying to take care of two giant (albeit cuddly) marmoset babies is a lot of work, but marmoset moms have help from an unusual source – the menfolk. Marmosets have evolved a curious mating system. Many of the species are polyandrous: poly meaning “many”, and “androus” meaning “man”. One female marmoset mates with multiple males – usually two, a pair of brothers. These brothers then help raise the offspring. And they’re good parents, carrying the kids around all day so the mother can forage, and then handing them over one-by-one so that the mother can nurse. While the mother nurses, the dads hover nearby nervously, waiting to get their babies back.

Polyandry is a rarity in nature (or, it’s just not been found very often because it makes conservative male biologists uncomfortable). The reason it’s uncommon is because, genetically, it’s a losing game for males. If multiple males are mating with a single female, only one of the male’s sperm will fertilize the egg. Only one male become the biological father, and only his genes are passed on. The other males make zero contribution to the next generation. If both males stay and help to raise the offspring, the non-father is just compounding his loss – he hasn’t reproduced, and instead of spending time and effort hitting the dating scene, he is helping to raise another male’s offspring. That’s a poor evolutionary strategy.

If only Edward and Jacob were related, then this situation could have easily been resolved.

If only Edward and Jacob were related, then this situation could have easily been resolved.

So how to get around this problem and explain the evolution of polyandry in marmosets? First, the two dads are brothers, which helps. Because of their close genetic relatedness, they’ll be related to the offspring regardless of which one of them is the parent. If it’s difficult to find any other females, or they have a short life-span, then polyandry can be a workable strategy. But marmosets have another advantage: they are mutant freaks.

More “scientifically”, I guess, the advantage is germline chimerism. The chimera is a fire-breathing monster from Greek mythology, with a lion’s body, a goat’s head protruding from its back, and a tail that ends with a snake’s head (she’s also the offspring of Echidna, who we discussed in an earlier post). The Greek name translates approximately to “she-goat”, which a really bad description, and the earliest reference is in the Iliad:

“He [the King of Lycia] ordered Bellerophon to kill the Chimaera -

grim monsters sprung from gods, nothing human,

all lion in front, all snake behind, all goat between,

terrible, blasting lethal fire at every breath!”

Bellerophon, being a good hero, succeeds and kills the chimera, much to the annoyance of the king of Lycia (who had wanted Bellerophon to die for complicated and soap-opera-y reasons). Since then, chimerism has been adopted as a genetics term, used by geneticists who want to show people that they’ve read the classics (which was totally not what I was doing, by the way).

A chimera.

A chimera.

Genetic chimerism occurs when one organism contains more than one population of genetically different cells. Chimeras are composites, containing full-functioning genetic material from multiple zygotes. This results in individuals who, like the Greek chimera, are a mixture of different materials. Unlike the Greek chimera, they usually don’t have goats growing out of their backs.

Chimerism occurs in humans sometimes, the likelihood being increased when in virto fertilization is used, but is often undetectable. In rare conditions, when the zygotes that form the chimera are of opposite sex, the resulting individual may have some intersex traits. Chimerism in humans briefly came to the fore in 2004, when American cyclist Tyler Hamilton was accused of blood doping – his blood tests showed evidence of “foreign blood populations.” Hamilton’s lawyers, perhaps also eager to display their knowledge of literature, offered up the defence that Hamilton was a chimera. It was a bit of a non-starter, and Hamilton was banned from racing for two years.

Pictures of disgraced cyclists? Boring. Pictures of baby mythical creatures? Wonderful.

Pictures of disgraced cyclists? Boring. Pictures of baby mythical creatures? Wonderful.

Marmosets are not professional athletes, but if they were, they could use the “chimera defence” in good conscience. Marmosets are fraternal twins: two sperm meet two eggs, and form two embryos, they just happen to share the same space. In fraternal twins in most animals a separate placenta fuels each embryo. But in marmosets, the two placentas fuse, causing a situation helpfully called placental vasular anastomoses between the two embryos. In non-jargon, it means that the two embryos, through the placenta, exchange stem cells. After birth, each marmoset brother contains part of the others DNA.

This unique arrangement helps to explain polyandry. Regardless of whose sperm actually fertilizes the female’s eggs, both brothers will contribute some DNA. Both brothers end up being the fathers of both new-born offspring. This creates a paternity headache that not even Maury could sort out – but it also makes it worthwhile for the two males to stick around and help raise the babies together. Which is great for the mom – she gets two permanent babysitters and plenty of “me” time.

Credit: Jupiter at imagefav.com

Credit: Jupiter at imagefav.com

Neil Griffin

Literature Cited:

Niblack GD, JR Kateley and N Gengozian. 1977. T- and B-lympocyte chimerism in the marmoset. Immunology 32: 257-263.

Sweeney CG, JM Ward and EJ Vallender. 2012. Naturally occurring, physiologically normal, primate chimeras. Chimerism 3:43-44.

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The Harmattan: Winds of Life and Death, Part II

Posted on April 4, 2013 by

The Harmattan: Winds of Life and Death, Part II

Contrary to popular belief, true rainforest is not a tangled, fetid mass of clinging vines and threatening shadows. It doesn’t require a machete and a sense of determination to traverse (though it’s best to watch your step – the snakes camouflage well, and don’t always flee from intruders). Instead, rainforests are cathedrals.

Tall, ancient trees buttressed with tremendous roots shape the architecture of the forest, and overhead the canopy seals out light and sound. The floor of a rainforest can be a surprisingly cool and quiet place, like a monastery cloister in the silent hours before matins. Small breaks in the overhead branches allow shy rays of light. The trees dilute the sun’s tropical power, until only dapples glaze the forest flower – more beautiful than the shapes cast by any stained glass window.

The massive buttress roots of tropical rainforest trees.

The massive buttress roots of tropical rainforest trees.

But unlike a cathedral, where life occurs mostly on the stone floors and in musty hallways and uncomfortable pews, life in the rainforest flees the depths and stretches to the sky. Vines and lianas wrap crawl towards light. Monkeys leap from branch to branch 30m above the ground, and hummingbirds zip through the canopy, dodging branches at super-human speeds.

A female squirrel monkey with a baby leaping through the canopy. Credit: Gregory G and MB Dimijian.

A female squirrel monkey with a baby leaping through the canopy. Credit: Gregory G and MB Dimijian.

At the top of the forest, in the highest level of the canopy – the emergents – flowers grow. Orchids wrap their roots around the sturdy branches of trees, and unfold their petals to capture sun and rain. Orchids are epiphytes. They grow on trees or rocks, but do not parasitize their hosts. This allows them to grow in places inaccessible to other plants – for instance, 45m above the forest floor – but it is a lifestyle that brings its own set of challenges.

An orchid attached to a banyan tree.

An orchid attached to a banyan tree.

High above the forest floor, orchids can gather water and sunlight, but they are otherwise divorced from the nutrient cycle – they cannot access the circle of growth, death, and decay that infuses the soil with endlessly recycled nutrients. To acquire the nutrients necessary for growth, orchids in the Amazonian rainforest rely on a more fickle source – they rely on the harmattan.

The harmattan can deposit as much as 190kg per hectare of mineral rich dust every year – it is nature’s own fertilizer. Over the course of a year, hundreds of millions of tons of dust are carted around the world. Much of this dust is dumped in the Amazon basin, where it fuels rainforest growth on a massive scale. Looking back through the geological record, palaeontologists and geologists noticed something interesting: fluctuations in rainfall over North Africa correlate closely with the expansion and contraction of the rainforest. High rainfall in North Africa leads to less dust being tossed around the world by the harmattan, and a shrinking in the rainforest; periods of drought in the Sahel cause more dust to be carried to the Amazon, and an increase in rainforest size.

Mapping global dust flow. Dust from the Gobi desert fertilizes Hawaii, the same way the harmattan fertilizes the Amazon. Credit: Kellogg and Griffin 2006

Mapping global dust flow. Dust from the Gobi desert fertilizes Hawaii, the same way the harmattan fertilizes the Amazon. Credit: Kellogg and Griffin 2006

For a long time, this theory relied on climate modeling and inference from the geologic record. The trace minerals deposited in dust plumes are difficult to measure, requiring elaborate and expensive laboratory techniques (I know – I once tried to measure the trace levels of iron in seawater, it was a frustrating experience. But then, I’m a mediocre chemist). However, advances in technology have allowed scientists to collect dust deposited in the Amazon and compare it with North African soil – the two are virtually identical.

If that’s not enough for you, the harmattan sometimes brings life in more direct ways. In 1994, researchers in the Caribbean made a curious discovery – a new species of grasshopper. Or at least, new to the Caribbean. It was well known in its home territory – North Africa. Caught in the harmattan, the grasshopper had been carried across the Atlantic. Despite its stressful week, it lived. Tough little buggers.

If you think you're having a bad week, take a moment and spare a thought for this guy.

If you think you’re having a bad week, take a moment and spare a thought for this guy.

The harmattan brings both life and death. It’s dust triggers toxic blooms in the ocean, while at the same time fuelling rainforest growth. The dust of North Africa is a finite resource – researchers estimate that the harmattan will deposit nutrients for another 1,000 years. After that, it’s difficult to tell what will happen. The Amazon may shrink, as it has in historical times, but Florida’s beaches will be safe for swimmers.

The driest landmass on Earth fuels the growth of the planet’s lushest rainforests. Without the desert, the rainforest would die. Two massive ecosystems, separated by an ocean, are intimately connected. Changes in one reverberate around the world to affect the other. The harmattan is a powerful reminder of the interconnectedness of life on Earth.

 

Neil Griffin

Literature Cited

Bristow CS, N Drake and S Armitage. 2009. Deflation in the dustiest place on Earth: The Bodele Depression, Chad. Geomorphology 105: 50-58.

Bristow CS, KA Hudson-Edwards, A Chappell. 2010. Fertilizing the Amazon and equatorial Atlantic with West African dust. Geophys. Res. Let. 37

Garrison et al. 2003. African and Asian Dust: From Desert Soils to Coral Reefs. Bioscience 53.

Stoorvogel JJ, N Van Breemen and BH Jassen. 1997. The nutrient input by Harmattan dust to a forest ecosystem in Cote d’Ivoire, Africa. Biogeochemistry 37: 145-157.

Swap R, M Garstang, S Greco, R Talbot and P Kallberg. 1992. Saharan dust in the Amazon Basin. Tellus 44B: 133-149.

Prospero, JM. 1996. Saharan Dust Transport Over the North Atlantic Ocean and Mediterranean: An Overview, in The Impact of Desert Dust Across the Mediterranean. Editors: S Guerzoni and R Chester. Kluwer Academic Publishers: Nowell, USA.

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