Cuttlefish strike a pose for 3D camouflage

In the game of hide and seek, cuttlefish have the upper hand. These chameleons of the sea are astonishingly good at disappearing: they can instantaneously change the colour of their skin to blend in with the background, matching even the finicky details like the pattern of coloured rocks on the ocean floor.

Divers have long known that cuttlefish are masters of the 3D camouflage game, too, and new research from the Wood’s Hole Oceanographic Institute has revealed how they do it.

Alexandra Barbosa, a graduate student, and Dr. Roger Hanlon were interested in the way cuttlefish strike a pose when trying to hide. After encountering a predator, these octopus-like animals will flee among the corals, rocks and algae, and freeze with their arms contorted into shapes that mimic nearby objects – a feat made all the more impressive by the fact that cuttlefish arms can bend in any direction. Some birds and insects are also known to camouflage themselves with body posture, but few come close to cuttlefish in shape-shifting flexibility (see photos of cephalopod camouflage in the wild here).

To understand just how they do it, Barbosa and her colleagues in Dr. Hanlon’s lab presented captive cuttlefish with some highly unusual surroundings: jailbird stripes, in black and white. In response, the cuttlefish got theatrical, raising their arms roughly parallel to the angle of the stripes. And when the researchers shifted the angle of the background image, the cuttlefish stretched their arms into a new position in an attempt to stay hidden.

Cuttlefish posing on artificial backgrounds

Cuttlefish posing against different backgrounds. Modified from Barbosa et al. 2011 (see Figure 1).

Intriguingly, not all of the ten individuals tested were able to match the angle perfectly all of the time – but these quirks may not be surprising given that cuttlefish camouflage is so complex. After all, in nature cephalopods get to choose their own hiding places, a decision that might involve several different factors. According to the researchers, camouflaged cuttlefish are even known to gently wave their arms to match the movement of the underwater plants they are trying to mimic.

These results are a clear demonstration that cuttlefish use vision to guide their 3D camouflage, since the study animals matched a flat background image. Moreover, Barbosa and Hanlon have shown that shape-shifting cephalopods can easily handle scenarios that would never occur in the environment where these behaviours evolved, and adjust just as flexibly to this artificial environment as they do in their natural habitats.

Captive experiments like this are just the first step in understanding how cuttlefish use visual cues to hide, and some big questions remain. For instance, little is known about how cuttlefish can detect and match colours so well despite the fact that they are, in effect, colourblind – Hanlon has found that giant Australian cuttlefish can take on the colouration of rocks on the ocean floor even in the middle of the night.

These remarkable split-second decisions about where, and how, to hide might also help us understand something bigger. Strategic camouflage is just one aspect of the surprising intelligence of cuttlefish, which have the largest brains for a given body size of any invertebrate – these animals are also able to learn and communicate with one another at a level that rivals many land-based animals. It will be intriguing to see where hide and seek fits in to the history of cephalopod brain evolution.

Further Reading

Barbosa, A. et al. 2011. Proceedings of the Royal Society B. In press.

How I learned to respect the peahen

Written for the Los Angeles Arboretum.

Meep meep? More like “Honk honk!”

Arboretum regulars will no doubt recognize the call of a startled peahen, but you may not be aware of the clever ways they use it. Not that they try to boast or taunt the enemy, necessarily, but I’m starting to think that the birds at the Arboretum owe a lot to their version of the Road Runner’s call.

How do I know? Some background is in order here: I’m the tall blond woman who has been hanging around the Arboretum morning and night for the past few years, overdressed and hauling a camera, a pair of binoculars, some peanuts and, if I was lucky, a peacock. Working at the park each spring, I often wished I had more time to chat with visitors. But I was preoccupied, and the life of an ornithologist can sometimes feel like that of Wile E. Coyote on a bad day.

For the past four years, I’ve been chasing peafowl across the continent – from Arcadia in February to Winnipeg, Toronto and New York in May and June. Incidentally, the Bronx Zoo is the only place in North America that even comes close to the Arboretum in sheer number of peafowl. Three years into my PhD in biology, and I’ve spent literally hundreds of hours watching these birds.

You may be wondering what got me into this mess.

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Monkeys draw from memory

We’re a little bit closer to understanding what it’s like to be a monkey, and it’s thanks to the same technology that powers your smartphone: the touchscreen.

The latest victory for touchscreens is in the field of memory research. Scientists have been studying this ability in animals for decades – some birds, for example, are remarkably good at keeping track of the little details they use when foraging. Florida scrub jays collect thousands of acorns in the fall, hiding them as reserves to help get through the winter. Proof that scrub jays can keep track of multiple pieces of information about their caches – including the type of food, its perishability, and how long it ago it was stored – came from some clever experiments where jays learned to store worms and peanuts in sand-filled ice cube trays in the lab1. Rufous hummingbirds perform a similar feat. They can keep track of flowers on their daily foraging routes, including when the nectar for each one should be replenished, and time their visits accordingly. How do we know? Biologists taught hummingbirds in the Alberta Rockies to feed at artificial flowers that could be refilled on schedule2.

There is also a long history of research on the mental capacities of our closest animal relatives, primates. Rhesus macaque monkeys, a lab favourite used in countless studies of pharmacology and physiology, can easily keep track of a set of objects and spot the difference if you show them an altered version later on3. Not surprisingly, primates seem to have better memories than birds. Baboons can learn thousands of different photographic images and retain these memories for years – incredibly, when this particular study went to press, the baboons were up to 5000 and still hadn’t maxed out their capacity4.  Pigeons, on the other hand, hit a memory wall at roughly 1000 images4. These abilities might prove useful to primates like the chimpanzees living in the Taï National Park of Côte d’Ivoire, Africa. They make extensive use of their vast forest habitat, visiting hundreds of fruit trees that ripen on different schedules5. The Taï chimps can apparently remember where the especially productive trees are, and will often travel longer distances just to get there5.

But there is something missing from this research. It has to do with a subtle distinction in the way memory works: the difference between recognition and recall. Recognition is the ability to identify something because you’ve experienced it in the past. Recall, which can be more difficult, involves retrieving that memory on demand. Ben Basile and Rob Hampton liken it to the difference between a police lineup and talking to a criminal sketch artist. To recognize something is to see it and sense familiarity; to recollect is to create that experience in its absence.

So far all we have been able to study in animals is recognition. Without language, we can’t get them to describe their memories – until now, that is. Basile and Hampton, two scientists from the Yerkes National Primate Research Center in Atlanta, have figured out how to get monkeys to act like criminal sketch artists6.

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Elections are like peacocks

Both are loud, and both cause colourful flashy things to pop up on lawns everywhere. And much like elections, the peacock’s train is a costly endeavour. The species might be better off in terms of survival and abundance if they could just do away with those feathers. In terms of sheer waste, they remind me of the Green party pamphlets in our apartment building entrance way. They were stuffed blindly into all of the available mailboxes – which happen to be for street level businesses on our downtown block, not residents. Nice.

Peacocks and elections are both supposed to experience strong positive feedback effects. In politics, momentum can lead to rapid climbs in popularity. Sexual selection can be similar: as Ronald A. Fisher pointed out, exaggerated male traits can potentially evolve through a process of positive feedback. If enough females prefer the particular male trait initially, and the next generation inherits both the female preference and the exaggerated male trait, it can kick-start a runaway process of sexual selection to extremes.

Despite claims to the contrary, we don’t actually know whether Fisher’s runaway process contributed to peacock evolution. But it may be reasonable to assume that it played at least some role: positive feedback should set up easily so long as mate choice is not very costly for females2.

Thinking about peacocks gave me an insight that may have cured my allergy to all things political, at least temporarily. Not that I don’t care about the election – I do – but I can’t get over my frustration at the kinds of things that count as good arguments in the political sphere. Here’s an example: I’d like to learn more about the Green party, but they seem to support a whole lot of pseudoscientific nonsense. Apparently their health care platform includes homeopathy and various other forms of alternative medical quackery. How can we be sure they won’t apply the same less-than-rational approach to the environment? If only there could be “one true party”, I thought after the leaders’ debate – a notion that, briefly, made me wonder whether I might be a closet fascist.

This doubt came up again when I was reading an article in this week’s Nature about the effect of social media on research priorities. It focused on the controversial and totally unproven “liberation procedure” for MS – extremely popular in Canada but, oddly enough, nowhere else1. The article mentioned that Michael Ignatieff has stated his support for clinical trials of the treatment, despite the recommendation by a panel of CIHR experts that a clinical trial would be premature without further evidence from observational studies1. The authors of the Nature article – a group of doctors and medical researchers in Canada – ended up somewhere close to Ignatieff’s position nonetheless. They concluded that the benefits of a full-blown experimental trial might outweigh the costs if thousands of social media-influenced patients are travelling outside of the country to receive private treatment anyway, “exposing themselves to the risks and costs”1. In other words, popularity is an important – and rational – consideration when it comes to medical science.

I have two things to offer for election day. First, there is a good summary of where the major parties stand on science and research funding here. Some are a lot more rational than others.

On to the peacocks. Democratic elections, like sexually selected traits, are communal illusions. Money is another example. The more you accept them, the more you believe in them, the better they work.


  1. Chafe, R. et al. 2011. Nature 472: 410-411.
  2. Lande, R. 1981. PNAS 78: 3721-3725.

Furious about eyespots

I think I flubbed an interview this week. My supervisor Bob and I just published a paper that is getting some press, because it addresses a recent controversy about the peacock’s train1. Eager for the interview with Nature News, I wasn’t exactly prepared with good lines for the reporter to go on – and I wonder if that’s why he had to pump up our story as a “furious debate”2.

In truth, most of the “debate” played out in a flurry of news articles back in 2008. That was when Mariko Takahashi and her colleagues in Tokyo and Kanagawa published the fruits of their exhaustive 7-year study of the peafowl at the Izu Cactus Park in Shizuoka, Japan3. I’ve never met Takahashi, although I did meet her supervisor and one other player in this story at a conference back then, and all were quite friendly. But the title of Takahashi’s 2008 paper, “Peahens do not prefer peacocks with more elaborate trains” was a direct jab at an earlier one, “Peahens prefer peacocks with more elaborate trains”, by Marion Petrie in the UK4. Takahashi and her coauthors had the difficult task of proving a negative – and they did it pretty convincingly, with the aid of a much more extensive data set than anyone had gathered before with this species. The upshot? For a peacock in Japan, having a bigger train ornament doesn’t necessarily win you any favours with the ladies.

Bigger in terms of the number of eyespots visible in the ornament during courtship, that is; males have about 150 on average, each on the end of a single feather. The results of the Japanese study were in direct contradiction to Marion Petrie’s earlier work as well as some recent studies of peafowl in France suggesting that eyespot number is often correlated with male mating success4,5. What’s more, in the 1990s Petrie had confirmed the causal effect of eyespots by showing that you could alter a male’s fate just by removing about 20 of them6.

Peacock in flight

Taken at the Los Angeles Arboretum in 2009. Photo by Roslyn Dakin.

The Japanese team proposed a rather bold new hypothesis. Perhaps the cumbersome, ridiculous train ornament is obsolete – a relic of sexual selection past, no longer used by females in quite the same way as it was when it first evolved3.

This was taken up with gusto by the news media. Check out the headlines: “Peacock feathers: That’s so last year”, “Have peacock tails lost their sexual allure?”, “Peacock feathers fail to impress the ladies”. Amusingly, this last article was also published with the title, “Female peacocks not impressed by male feathers” by Discovery News7-10. Males could probably be forgiven for striking out with those elusive female peacocks, since they don’t actually exist.

Headlines aside, Takahashi’s interpretation is somewhat of a concern. Here’s why: creationists picked up on this story too11.

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Cultured tastes

Dinner in Shippagan, New Brunswick. Photo by Charlie Croskery.

We drove halfway across the country for the party, but the main course alone was worth the trip. When the pig was finally hauled out by a crew of strapping male relatives, the guests at Anne-Claire and Martin’s wedding converged at the carving table. Small children, I’m told even a Jewish person or two – nobody could resist a taste of warm skin ripped straight off with a knife. Not after seeing (and smelling) the thing turn that entire August afternoon.

I doubt we would have made the cross-country trip if charlem was on the menu. That’s what Vladimir Mironov, an expert in stem cell and tissue science, calls his latest culinary invention. Mironov’s product is grown right in his lab at the Medical University of South Carolina in Charleston – hence the name, short for Charleston engineered meat.

In a handful of labs around the world, scientists like Mironov are working on a curious agricultural problem: how to generate edible meat products without the farm – or the animals1,2. Their solution is to grow meat from animal stem cells. Some use cells taken from embryos, while others, like Mark Post at Eindhoven University in the Netherlands, are looking into the feasibility of growing muscle satellite cells taken from adults1. These can be extracted from domestic pigs or fowl with a quick and painless biopsy, and used to seed in vitro cell cultures.

In the future, this could be an easier way to serve a crowd. Like human cancer cell lines immortalized in a Petri dish, satellite cells can potentially go on multiplying forever in the lab, so long as you give them enough growth medium. Vladimir Mironov sees industry ultimately growing “charlem” – his cultured turkey – in bioreactors the size of football fields that he likes to call “carneries”. He imagines a world where fresh charlem is also grown at your local grocery store, in miniature appliance-size versions of the bioreactor machines3.

His work is, in part, funded by PETA, in an effort to stem the unmeasurable output of animal suffering caused by industrial agriculture. In 2008, the animal rights group also announced their in vitro chicken prize for the first person to develop a commercially viable product and sell it in at least 10 US states. To be eligible, the chicken also has to pass a panel of tasters when breaded and fried. The $1 million dollar reward is still up for grabs3,4.

No doubt this is a noble goal*. Large-scale meat production is an environmental scourge. The North American “meat guzzler”, as Mark Bittman calls it, is not sustainable6. Influential food writers like Bittman and Michael Pollan, and others including star chef David Chang, have been urging us to rethink our eating habits for years7. Environmentally, there’s a lot to be said for the alternatives: we could save a lot of resources by switching to the Asian practice of using small amounts of meat to complement dishes where vegetables and grains are the main event.

According to Nicholas Genovese from Vladimir Mironov’s lab, “Animals require between 3 and 8 pounds of nutrient to make 1 pound of meat. It’s fairly inefficient. Animals consume food and produce waste. Cultured meat doesn’t have a digestive system.”3

He’s right, of course. But his last point also happens to be the very reason charlem will never make it: meat from an animal is more than the sum of its in vitro parts. Want nutrients? We’ll have to add those in at the factory. Vitamin B12 and iron – two of the main nutritional reasons for eating animal protein in the first place – come from gut bacteria and blood1. You can’t get them from muscle tissue in isolation. Want taste? Let me see if we have an additive for that too…

Scientists may figure out how to culture meat efficiently in the lab, but it won’t be a viable solution to our agricultural problems, at least not anytime soon. The trouble with fake meat is that it’s up against evolution on two fronts, and, ironically, morality on a third.

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Dating the rainbow

Buttermere Lake, with Part of Cromackwater, Cumberland, a Shower

The truth is beautiful in Buttermilk Creek. That was the Texas site of a recent major archaeological find. In the village of Salado, just a couple hundred metres downstream from an important cache of artifacts of the early American Clovis people, anthropologists uncovered something just a few centimetres deeper1. In geological terms, that usually means older – and the assortment of stone tools found by Mike Waters and his team might be the definitive evidence needed to overturn the longstanding “Clovis first” theory.

“Clovis first” is the idea that North America was initially populated by a group of big game hunters known for their interchangeable fluted spear tips – a portable tool that fit well with the nomadic lifestyle. I won’t get into the details (see elsewhere), but many researchers now believe that other migrant groups arrived from the north well before Clovis domination. For example, fishing tools found in California’s Channel Islands provide evidence that a seafaring clan made its way south by hopping along the coastline2.

I also won’t cover the Buttermilk Creek find (again, see elsewhere for this). But there is a poetic element to this discovery worth sharing. The proof that the Buttermilk Creek people arrived ahead of Clovis hunters comes, not from the usual radiocarbon dating methods, but from dating the rainbow.

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Another reason for eggs

Roman soldiers used them for protein1. In Mexico, men steal them from endangered sea turtles for their supposed effects on virility2. Bird eggs and roe, the ripe ovaries of fish, have a rich balance of proteins, fats and minerals – nutritionally, almost everything a predator needs. The whole point of these things is to feed something for an extended period of time. It’s no wonder eggs are so delicious.

The applications go beyond adding energy to our diets and structure to baked foods. Laying hens also contribute to medicine. Fertilized chicken eggs are used to grow viruses for mass production of vaccines. In 2007, scientists figured out how to genetically engineer hens to incorporate certain cancer-fighting proteins right into their egg whites, in a more efficient way to manufacture drugs that has been dubbed “pharming3.

This morning, enthusiasts have yet another reason to celebrate, since a new study suggests that bird eggs might hold even more promise for medical research.

It has to do with migration, but not the kind you’re used to hearing about with birds. Cellular migration refers to the movement of cells within an organism during growth or embryonic development. For a long time, biologists studying this behaviour focused on the movement of single cells in isolation. In the last decade, however, the focus shifted to cells moving in a large, cohesive group. This collective migration is a fundamental part of gastrulation and neural crest development – two of the necessary steps for turning a blob of cells into a fully formed embryo during development (watch a time lapse video of this process in zebrafish).

Collective cell movement, or epithelial migration, occurs on a grand scale during bird embryo development. Every fertilized egg contains a tiny blastula, the hollow ball of cells that will eventually become a fetus. Early on, the cells of outer blastoderm layer of the ball start to expand across the vitelline membrane that surrounds the egg yolk, in a process known as epiboly. Eventually, the expanding sheet of cells envelops the entire yolk – a requirement for the yolk sustain the embryo during its transformation from a ball of cells into a viable chick.

Bird embryo and yolk

A chicken embryo grows while attached to its yolk, because of epiboly. Modified from drawing by D.G. Mackean.

This around-the-yolk migration happens rapidly, within days. From the perspective of a single cell, it’s a feat that bioengineer Evan Zamir likens to “an ant walking across the earth”4. And we still don’t know exactly how birds do it, with their humongous yolks; so far, most research on epithelial migration has involved other organisms.

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I can haz toxoplasmosis

In which you will learn why online cats are so attractive, and discover a new way to lose hours to the internet.

First, the cats. Charlie and I were hashing out the finer points of Facebook, memes and internet superstars, when, in frustration, I brought up his most hated animal.

“Look. Cute baby videos and LOLcats are popular because people send links to their friends. Nobody sits down and says, ‘Well it’s quarter to 10, the same time I always drink my coffee and look for the latest cute cat photos on the–’ ”

Self defeat and laughter mid-sentence, when I remembered living with my friend Jessica in Toronto. She had a brutal job in psychiatric research north of the city. After a hard day, that was exactly what she did. Nothing cheered this woman up like online cat research.

Felis catus is a polarizing species. Some people despise them. Ancient Egyptians and cat ladies have made a religion out of them. The story goes that wild cats were first domesticated in ancient Egypt for useful things like keeping rats out of grain stores and killing poisonous snakes, but this might be more myth than reality. Cats were probably kept around as tame rat-catchers much earlier, certainly before recorded history, and very likely around the beginning of agriculture itself. People were depicting cats on pottery 10,000 years ago1. Cyprus can boast the first Stone Age cat lover. A 9,500 year old burial site on the island is the earliest evidence of humans bonding with these animals, since a cat was intentionally buried alongside a human body there2. The fact that the cat was not butchered, and the inclusion of decorative seashells and stones in the grave, prove that cats had achieved cultural importance beyond their agricultural utility back then.

European wildcat

The European wildcat Felis silvestris is a close relative of the earliest domesticated species. Photo by Péter Csonka from Wikimedia Commons.

But could the cat haters be right – is there something off about feline love? After all, cats aren’t really that useful, at least not when compared to dogs. Dog people might be pleased to hear that when you consider all living and extinct canid and felid species, dogs have bigger brains than cats – probably because they tend to be the more social animals3. Indeed, dogs adapted readily in response to domestication, evolving a number of cognitive abilities that make them particularly good at understanding human gestures – much better, even, than chimpanzees4. Naïve 4-month old puppies will quickly learn what it means when a human points, without any training or close contact with humans beforehand5. Cats can do this too, but they require a lot more effort to learn how6. Dogs can detect certain forms of cancer in humans by smell, and they are often the first ones to notice that something is wrong with their owners7. I have yet to find any high profile studies on feline pathologists. Which raises the question: if cats could do it, would they care enough to try?

And in a bizarre twist, there’s reason to think that our magnetic attraction to cats might be the result of a real parasitic disease.

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Employed science

It’s when applied science gives back, contributing a piece to the basic research puzzle.

Jaded grad students like me get a warm fuzzy feeling when we hear about people reaping unexpected benefits – economic or social – from the results of pure science. Last night I was reminded that this can work in the opposite direction.

Matthew Mecklenburg and Chris Regan, two physicists from UCLA with interests in quantum theory and its applications for sustainable energy, wanted to design a better transistor. Instead, they discovered something fundamental about the structure of the universe1. Hidden from our eyes and our finest instruments, the space that surrounds us might be more like a chessboard than a continuous expanse.

Mecklenburg, a grad student, was investigating graphene as a potential material to make more efficient transistors – the little bits of silicon that allow computers and essentially all modern electronic devices to function. He needed some precise measurements of the way light interacts with graphene at the nanoscale, to assess feasibility of the new design. These experiments gave Mecklenburg a quantitative picture of the way electrons hop around in the lattice of carbon atoms in graphene. And that’s when the chessboard struck.

Mecklenburg and Regan realized that the hopping behaviour of electrons in graphene was formally equivalent to what happens when an electron flips its “spin” – a theoretical concept that has remained an enigma since it was described in the early 20th century.

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Identity evolves

Everyone is special.” The paradoxical refrain of baby boomer parents to their millenial offspring is true, so long as you’re a rodent living in a large, stable group of good communicators.

I recently wrote about the phenomenon of identity signals in animals, where variable colours and patchy-looking patterns can provide signatures of individuality, much like the human face. These are not limited to the visual domain. Think of how easily you can recognize a person’s voice – even someone you don’t know very well – from just a few lines of speech, like when a celebrity turns up in an animated movie.

But I didn’t have a chance to cover the latest news on this topic. In some very plain looking rodents, we now have evidence that individuality evolves1. Some of the plainest looking critters, like the Belding’s ground squirrel shown below, have the most distinctive snarfs and grumbles – and it all has to do with the number of group-mates they typically interact with.

Belding's ground squirrel pups

Two Belding’s ground squirrel pups peek out of a burrow. Photo by Alan Vernon from Wikimedia Commons.

The new results came out this month in the high profile journal Current Biology. Previously, researchers had looked for the evolution of individuality in a handful of bird and bat species. The prior studies examined distinctiveness in the begging calls offspring make to their parents, contrasting pairs of closely-related species that vary in the number of offspring in shared “crèche” or communal nest sites2,3. But nobody had tackled the evolution of individuality in a broad context.

Until Kim Pollard, that is. Pollard, a recent PhD graduate from UCLA, and her supervisor Dan Blumstein decided to look at this question in the social marmots. You might remember Blumstein from another recent post; his interests range from mammal conservation and environmental education to the bioacoustics of movie soundtracks.

For Kim Pollard’s study of identity signalling, marmots were an ideal choice. Marmota is a large genus of 14 different species in the squirrel family, all social, and all with their own alarm calls that they use to warn neighbours and family members about nearby predators. Species like the yellow-bellied marmot and Richardson’s ground squirrel also have the ability to recognize each other based on the unique sound of these calls4,5.

Crucially for Pollard and Blumstein, social group size also varies in the genus, ranging from about 5 to 15 individuals per clan or family group. This allowed the authors to test the hypothesis that group size has been an important factor in the evolution of distinctiveness, since, as they put it, “The bigger the crowd, the more it takes to stand out.”

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To kill bias, gather good data

I hate myself for this: I have the worst sense of direction.

For the entire year when I was living in my first apartment in Kingston, I would take a circuitous route along King Street and then up Princess on my way home from the Kingston Yacht Club. Nearly two kilometers, when walking up West Street would have got me home in half the time. As Charlie said when I revealed this to him, “Two sides of a triangle is always greater than one.”

It’s not that I didn’t know grade school geometry, or that I wanted a more scenic route. I just stuck to the path I knew would get me there.

I felt a bit triumphant when I realized how long it can take Charlie when you ask him to pick up the milk. The last time I dragged him to the grocery store, I left him alone for a few minutes to use the bathroom, and returned to find him loading pineapple after pineapple after pineapple – painfully slowly, into the cart. We laughed, but I don’t ask him to come with me anymore. Alone, I can collect a week’s worth of food in less than 20 minutes.

I’m not ashamed to admit my navigational failings, either. My field assistant Myra and I happily agreed that our best strategy driving around Los Angeles was that we should always do the opposite of whatever we both thought was correct. It worked.

What I hate is my sneaking suspicion that I’m just a lame stereotype. Maybe I’m a terrible navigator because of biology; female brains are just not suited for getting around.

Hunter, gatherer

Modified from this cartoon. Original source unknown.

Recently, psychologists looked at this sex difference in what seemed like a neat field study of human foraging behaviour – in a grocery store1. Joshua New from Yale University, and his coauthors from UC Santa Barbara, set up a unique experiment in a California farmers’ market: they led men and women around the market, giving them samples like apples, fennel, almonds and honey. Then they brought the subjects back to a central location and asked them to point in the direction of those same food items.

These researchers wanted to test the idea that women outperform men at certain kinds of spatial tasks: while men are thought to be better at vector-based navigation, women might excel at remembering the locations of objects, because of the way foraging roles were divided up when our brains were evolving. It’s thought that in our hunter-gatherer past, big game hunting meant that men had to figure out how to bring heavy prey home by the most direct route. Women foraging closer to home needed a much different set of spatial adaptations2. It’s not that men are better at spatial reasoning in general, you just have to choose the right task3.

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Mind hacks for athletes and the rest of us

For a change of pace, I thought I’d cover two recent neuroscience findings in today’s post. It’s not all academic, either, since both of these studies might help improve your everyday life. Just sit back, suspend your disbelief and fire up the expectation and reward centers of your brain. You might be able to unleash your inner endurance athlete – or epicure, if so inclined – all through the power of the mind.

I’ll start with a surprising finding that I’ve tried to explain to other long-distance runners, who often take a small snack to eat in the middle of a run. I’ve seen the gamut, from orange slices to salty sports drinks and space-age energy gels. The rationale is that these foods quickly replenish the glucose available as blood sugar, the fuel for muscle contraction.

But if you are running for less than an hour, it is biologically impossible for these snacks to improve your performance. For one thing, the amount of carbohydrate that can be effectively absorbed from the stomach to muscle cells in an hour is too small to make any real difference1. And besides, our muscles can hold vast stores of energy in the form glycogen, more than we can possibly use in that span of time, anyway. Spend an hour on a stationary bike, cycling all-out, and you still won’t fully deplete the glycogen in your muscle tissue – so long as you were charged up to begin with2. And yet the snacks work, even in controlled laboratory tests of exercise performance3. No wonder athletes everywhere continue to use them.

Incredibly, this energy boost has nothing to do with caloric consumption, and everything to do with the act of eating.

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You are what you feed

What makes you you?

The problem of identity – and its flip-side, change – has been vexing philosophers ever since the discipline got started in ancient Greece. As early as 500 years BC, Heraclitus was musing about the ever-changing nature of a flowing river, recorded by his contemporary Plato with the enduring line, “You cannot step in the same river twice.”

This issue comes up everywhere. In an astronomy course I took at university, the professor gave us a mind-boggling assignment: calculate the number of atoms in your body that were once part of a living dinosaur. The answer was a lot, and though I don’t recall the exact number, the question could have just as easily been about sharing atoms with Heraclitus, or Plato, for that matter. The point is that most of the molecules in our bodies are being replaced and recycled, all of the time1. Like a flowing river, you are literally not the same bag of stuff that you were last year, or even last week; although a more accurate way to put it might be that you are a bag of somewhat different stuff than you contained before.

This raises a tough question. If a different collection of matter can be the same person, how much has to change before you aren’t yourself anymore? The implications are nearer than you might think. Organ transplants, bionic limbs and electronic implants – including devices implanted in the brain – are all within the range of current medicine. How much of a person’s body can we replace and still consider them to be the same person?

I don’t have the answer, and I’m not sure anyone ever will, although some would argue that it is a mistake to assume that there is anything like a constant “you” in the first place. For example, the philosopher Daniel Dennett contends that the idea of a continuous self is really just an illusion produced by the brain2.

Biology has a thing or two to say about the matter. It turns out that part of what makes you you is other species. Specifically, the ones living inside you: the veritable ecosystem of bacteria and other microscopic organisms inside your gut. Evidence is mounting that the microcosm within is an important part of who we are: it provides a unique signature of individuality. It can also determine future health. It might even be part of what defines us as human, since a new study shows that as we evolved from ape ancestors, so did our inner ecosystems3.

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A case of mistaken celebrity

They all look the same to us. Celebrities, that is. And by us, I mean academics.

The proof starts with peacocks. Last fall, I was working on some measurements I took of the crest ornament in these birds. Peafowl have this funky little fan of feathers on top of their heads, and though it’s not that small in the grand scheme of fancy bird plumage ornaments, the peacock’s five centimetre crest looks a bit ridiculous next to the metre-and-a-half long train.

Why bother having a crest when you also have a big train? And why do females wear crests too? In this species, the crest appears to be the only plumage ornament shared by both sexes. Here are some of my pictures from the field, taken on the cusp of the breeding season:

Crest ornaments of male and female peafowl

Crests of (a) male and (b-c) female peafowl. Scale bars are 10 cm. Photos by Roslyn Dakin.

Over the years, I’ve measured the crests of close to 150 birds. These data lend some support to the idea that the crest is a signal of health in both males and females, although it might work in slightly different ways for the two sexes1. As you can see from the picture above, there is a lot of variation in how the crests look – and it’s mostly on the female side of the equation. Almost all adult males have tidy looking crests like the one shown in (a), but females often have crests with a lot of new feathers growing in (c). It turns out that males in better condition tend to have fuller, wider crests. The healthiest females, on the other hand, have crests that look most like those of males, with all feathers grown out to the top level (b).

The extreme variability among females leads to an additional hypothesis, and it’s one that I can’t rule out at this time. Perhaps the crest is a signal of individual identity that the birds use to sort out who’s who in their social groups – just as faces do for us. A clue that this could potentially work for peahens is that my field assistants and I can do it. Once you spend enough time hanging around with these birds, you find yourself recognizing certain females that haven’t been captured yet (and that therefore lack identifying leg bands). Your first clue? Usually a unique pattern of crest feathers.

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The winning score

As Hollywood gets dolled up for the Oscars, fans at home might surprised to learn that a field biologist could tell us a thing or two about the winning films. Dan Blumstein, a behavioural ecologist who works, quite fittingly, at UCLA, is an expert on yellow-bellied marmots. He might also be the person to turn to if you want to predict the win in the “Best Original Score” category this weekend.

Although Blumstein does most of his work with wild marmots in the Rocky Mountains of Colorado, studying several facets of their behaviour and evolution, he recently published a paper on the science of movie soundtracks1. With Richard Davitian and Peter Kaye from the School of Music at Kingston University in the UK, Blumstein applied techniques from his research on marmot vocal communication to an entirely new question: why are Hollywood moviemakers so good at manipulating our emotions? The results pick up on a common theme in the way humans and other animals use sound.

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Not when cupid strikes

Raphael's The Triumph of Galatea

“Not when cupid strikes.”

That was Christine Drea’s response at the Animal Behavior meeting last summer. She had just given a talk on her latest study, showing the dramatic effects of hormonal contraception on the way lemurs communicate with the opposite sex1. I was asking her what advice she gives to women about birth control. On the 50th anniversary of the Pill, scientists like Drea were adding to the evidence that we might want to think twice about our widespread use of these drugs. The lemur research suggests that hormonal contraception could be replacing one “problem that has no name” – Betty Friedan’s idea of the dissatisfaction felt by modern women – with another2.

Like many primates, ring-tailed lemurs have a complicated system of signaling to one another through scent. Males are able to detect the sex, fertility and even the identity of a particular female by smell alone3. At first glance, the connection to humans might seem far-fetched, since our noses are pretty poor compared to other mammals. But we are relatively well-endowed when it comes to scent production: humans have more scent glands on the surface of our skin than any other primate4.

We also have some surprising olfactory abilities lurking beneath the surface. The classic example is the T-shirt test. In the 1990s, researchers at the University of Bern in Switzerland gave a group of men T-shirts to take home, with instructions to sleep and sweat in them over the next two nights5. When women were later asked to sort the dirty T-shirts based on pleasantness of smell, they did something surprising. Their rankings came down to genes: the more genetically distinct a man was from a female rater, the more she liked his scent.

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