Brawn over brains?

There’s no question that broadly speaking, big brains are smart. Take humans, for instance: our brains weigh in at about 3 pounds on average, nearly four times the size of the brains of chimpanzees (whose brains weigh in at less than a pound apiece).

What’s less clear is why. There are a number of theories: maybe intelligence evolved to give us a competitive edge in foraging, or maybe it helped us keep track of increasingly complex social interactions. Ideally, we’d like a theory to explain the evolution of intelligence broadly, so researchers have tried to these hypotheses across multiple species (for instance, comparing relative brain size and social group size among hoofed mammals like horses and deer1).

But brain size alone – even when scaled as a proportion of overall body size – is not an ideal measure of intelligence. The trouble is that small animals often have considerably higher brain-to-body mass ratios – ant brains, for instance, can weigh nearly 15% of their total body mass (the equivalent of a 20 pound human head!), and mice have about the same brain-to-body mass ratio as we do. So how can we study brain evolution, when even primates span a 3000-fold difference in body size (comparing a gray mouse lemur and a gorilla)?

Enter the encephalization quotient, or EQ, a measure of brain size relative to what we would predict, given that there is a curved relationship between brain size and body size (allometry is the technical term for this). It’s the best yardstick we have for the evolution of intelligence. Until now, that is.

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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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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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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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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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A royal waste?

Giant pandas are in the news again, this time for their annual date night at the Smithsonian National Zoo in Washington DC. But hardly a day goes by without a report somewhere on the latest captive panda birth, strategic breeding attempt or panda relocation.

A blogger at the London Review of Books compared the bears to members of the British royal family: both are suffering from shrinking ecological niches and in serious danger of extinction, hanging on by virtue of their marketing potential. The similarities don’t end there. Giant pandas, like royals, are expensive to house, with a fee of over $1 million per year for a zoo to lease a pair from China. Naturally, the breeding activities of giant pandas are as intensely scrutinized as those of Prince William.

This entails some surprising efforts when it comes to the pandas. The history of captive breeding for Ailuropoda melanoleuca is no sordid royal affair. It’s long, and for the most part, pretty unfortunate; zoos have been failing to produce heirs to the panda legacy for decades.

For starters, it’s nearly impossible to get the bears to mate in captivity, and it’s not just their deficiency in the looks department, as comedian Mike Birbiglia suggests. Captive pandas can’t seem to figure out a working sexual position1. Females often start things off all wrong by lying down, but the males are just as clueless. This led to panda porn: zoos started making videos of pandas achieving copulatory success, as training tools for the more hapless bears2. Other attempts to use Viagra on pandas were less encouraging, but the porn worked – for females as well as males – leading to a boom in captive births in recent years3.

Giant panda cub

Visitors can pay to see the cubs at the Chengdu giant panda breeding centre. File photo modified from

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Which animal would use Facebook most, if it could?

My poll in class last week was a popular one – a fact that I couldn’t properly enjoy, since Charlie came up with it for me in a fit of brain-dead incapacity. Charlie’s Facebook question elicited chirps of excitement, compliments and even a few drawings on the response sheets. Here are the results, ranked by favour among the students:

  • Chimpanzees: So they have opposable thumbs, and can “use the spacebar” (is this actually important in Facebook?). A number of students gave bonobos special mention, since they would probably want to keep track of all their casual sexual relationships.
  • Dolphins: Highly intelligent, social, and they might also be interested in monitoring multiple sexual conquests. Dolphins and migratory whales could use Facebook to keep in touch while roaming widely over the oceans – the long-distance relationships of the animal kingdom. For some reason, students in different tutorial groups who chose dolphins were inspired to draw them for me as well. Coincidence?
  • Parrots and other birds: Especially in species that have high levels of extra-pair paternity, birds could use Facebook as a form of mate-guarding to keep tabs on their social partner1,2. There are other reasons to think that songbirds might easily make the transition to internet gossip. Female black-capped chickadees, for instance, eavesdrop on the outcome of song contests between rival males, and use this information when deciding on a mate3.
  • Eusocial animals: Like ants or naked mole rats (the only known eusocial mammal). A couple of students also mentioned highly social meerkats, since living in groups of 10-40 individuals would require them to keep track of a lot of social information.
  • Other yappy follower-types: hyenas, seals, lemmings, and Yorkshire terriers all got a mention.

Charlie and I discussed it over dinner at the Iron Duke. My first thought went to ants, for their extreme group lifestyle. The problem is that ants don’t really care about what other ants do or think about each other. Insect sociality is all about the greater good: worker ants toil away for the colony despite having no hope of reproducing on their own. Ok, so maybe the internet isn’t conducive to real reproduction either, but ants just don’t have the ego required. Plus, as one clever student pointed out, a colony of eusocial animals are all very close genetic relatives of one another – and she tends to block family members from Facebook.

Charlie mentioned peacocks for spending so much time on courtship and preening, but I rejected that one too.

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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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Wherefore the mustache?

Ears, palms, toes, neck, and nose. In that order.

These are the grossest places for humans to have hair, according to Queen’s students. Ok, there were a few others that I didn’t mention. The upper lip, however, did not receive a single vote.

Last fall a number of men in the biology department grew competitive mustaches for “Movember” prostate cancer research fundraising. This required mass beard shaving on the first of November. Martin Mallet, known for his thick coat of fur, emphatic hand gestures and all-around intensity, suddenly transformed into a meek imposter. For the first time Martin had no probing questions for the speaker at the EEB seminar. I can’t help but wonder: if he did, would anyone have noticed?

I started to recognize Martin again when the hair on his upper lip attained visibility. Other men of Movember fared less well. It can’t be a good thing when the people who work in the same office as you don’t even notice your new, mustachioed face.

But what, if anything, is it for? My experience suggests that human facial hair serves as a male status signal. Is this why we evolved mustaches in the first place?

Inca Tern

Why do mustaches evolve? Inca tern, from Wikimedia Commons.

In class the other week we discussed Stephen Jay Gould and the trouble with adaptationism. Gould famously criticized the proliferation of sloppy adaptive reasoning in his 1979 paper “The Spandrels of San Marco and the Panglossian Paradigm1. He took aim at scientists who apply adaptive “story-telling” to nearly anything – from the colour of our skin to the size of our noses – in an unverifiable, unfalsifiable way.

It can be easy to jump on the adaptationist bandwagon, since these stories are often quite plausible. This may have been especially true when “Spandrels” was written, due to the rise of some revolutionary ideas about how to apply evolutionary biology to the study of social behaviour. There was plenty of new research to be done. Of course, many of the people doing this research disagreed with Gould’s characterization2. At its worst, adaptationist thinking might lead to some bad science, especially when it comes to human behaviour (where confounds are especially hard to control). But speculation is a necessary part of the scientific method, and adaptive reasoning can be a good place to start.

It is worth noting that Gould’s paper has been enormously influential. “Spandrels” has been cited well over 3500 times. I’m still waiting on citation number 3 for my Master’s research.

And yet, the response of the research community to the “Spandrels” critique has largely been, “That’s well said, but let’s get back to our field work.”2 In that spirit, consider the mustache. Can we speculate about it in a reasonable way, avoiding the big adaptationist pitfalls?

First of all, is this question worth asking?

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Science fictions

Fakery is not just for Hollywood films anymore.

Nature documentaries are full of it, from elegant narratives to some downright dirty tricks. This tradition goes back a long way: the myth that lemmings commit mass suicide to save their brethren from overpopulation was spread widely as as result of the 1958 Disney film White Wilderness. This is not trivial. The film won an Oscar for Best Documentary. The lemming story made it as far as a philosophy course I took in university (Science and Society PHIL203), where the instructor used it as an example of why we should doubt evolutionary explanations of human behaviour. The myth just won’t die, even though CBC exposed the lemming scam back in 19821. Journalists on The Fifth Estate proved that the mass suicide scene was actually filmed in downtown Calgary, not in the Arctic as Disney had claimed. The Disney crew used a rotating platform to push captive lemmings into the Bow River.

More recently, the BBC has come under fire for using captive animals to film some of the scenes in the Blue Planet series1. This seems justifiable to me, but some truly ugly practices have also been exposed, like baiting corpses with M&Ms to get footage for an IMAX documentary on wolves2.

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Field biology goes to Hollywood

One of the weirder things about my field site is that it is also a Hollywood set. A number of movies, TV shows and commercials have been filmed at the LA Arboretum, going back to Tarzan Escapes in the 1930s.

The Arboretum had a regular appearance in the popular 1970s show Fantasy Island. In the opening credits, a midget rings the bell in the Queen Anne Cottage. This is a historic building on the Arboretum grounds that was built in the by the same wealthy California businessman who started the peafowl population in the area.

You can catch the Arboretum in many other films, since it provides a convenient stand in for the jungle a short drive away from downtown Los Angeles. Examples: The Lord of the Flies, Anaconda, The Lost World, Congo, Terminator 2, The African Queen, and too many campy horror flicks to count (Attack of the Giant Leeches?).

Several things were filmed during my three seasons there, leading me to realize that making a movie is a lot like doing field biology. Here’s how:

1. The hours. Field biologists often have to keep the same hours as their study species, working for as long as the animals are active. For some ornithologists, this can mean starting at 4 am. We were lucky with peafowl. They are late risers, coming down from their roosts around 7-8 am. They also tend to take a long siesta in the middle of the day. This meant that we had to work two shifts, coming in for several hours in the morning and returning after lunch until sunset. It made for some long days.

Film crews also seem to work long hours based on the amount of light, since our schedules would often coincide.

2. Tedium and futility. Most of the time spent watching animal behaviour is watching them do very little. Here’s an example: we saw about 20 mating events in 2010, in 500 man-hours of observation time. That’s over 24 hours of sitting quietly for each copulation.

Catching the beasts can be a little bit more active, but you still feel completely useless 90% of the time. Your main activities include: waiting for the animals to show up, looking for the ones you haven’t caught yet, waiting around for your traps to work, and worrying about all the reasons why they aren’t.

A lot of jobs in Hollywood might not be so far off. When AT&T filmed a commercial at the Arboretum last year, we met a guy whose sole responsibility was to keep the peacocks away from the set. His boss gave him a bag of bird seed. It was the cusp of the breeding season, and the crew had decided to place their set right in the middle of one particularly dedicated male’s territory. The poor guy was literally playing tag with that bird all day.

3. Costumes. Important in Hollywood, but also useful when trying to catch birds. After a few weeks in the field, most tend to settle in to a uniform, wearing the same thing nearly every day. If it works and you’ll just be getting dirty again tomorrow, why change?

Field clothes

Waterproof jackets come in handy when catching large birds. From left: Will Roberts, Myra Burrell and Roz Dakin. Photo by Bonny Chan.

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Deep archives: Sex “pests” get more practice

Juvenile male peafowl practice their displays

Having finished my field work this year, I thought I’d keep up with this blog by writing about interesting things that other people have seen animals do.

To start: this BBC science news report on the discovery of a “sex pest” seal that attempted to mate with a penguin, brought to my attention by Rob Ewart (the original paper can be found here but you will need a subscription to the journal to read the whole thing).

Apart from the entertainment factor – the abstract to the scientific paper concludes, “we report a case of interspecific sexual harassment bridging the rank of vertebrate class” – there are a few interesting issues here. The first being, why on earth would the seal do this? The authors provide a few possible answers. Apparently these fur seals sometimes eat king penguins, so perhaps by some strange mis-wiring, predatory arousal translated into sexual arousal in this case. Alternatively, the seal may have been too young to find a real mate, desperation leading it astray. Or, intriguingly, the young seal could have been play mating, a form of practice for the real thing later on.

The second issue: why on earth would a scientific journal publish something like this? Is it really that unusual for hormonally-charged animals to make the occasional mistake? This year alone I witnessed a peacock give chase to a human female (with the characteristic “hoot” of excitement that accompanies all mating attempts), and I’ve seen several peacocks attempt the same with guinea fowl and squirrels. All of these events happened with males that were displaying intently but that hadn’t had any peahen visitors in quite some time. Is this paper really such a novel finding, or are the authors just as desperate as the seal?

On reflection, it’s probably important to document these unusual behaviours somewhere, since it would be an interesting outcome if they turned out not to be mistakes after all. Young peacocks, for example, will frequently display their undeveloped train feathers to each other (pictured above). This male-male display may seem futile, but I wouldn’t be surprised if the kind of dancing skill required later in life demands some practice. Similarly, in Costa Rica I remember hearing juvenile long-tailed manakins displaying long after the real mating season had ended, no doubt honing their skills for next year. There is even some evidence that the reason male manakins pair up for their co-ordinated display dances, even though only the dominant member of the pair will get to mate, is for the practice.

The full citation for the seal paper:

De Bruyn PJN et al. 2008 Journal of Ethology 26:295-297.

And two on long-tailed manakin displays:

Trainer et al. 2002 Behavioral Ecology 13: 65-69.

Trainer and McDonald 1995 Behavioral Ecology and Sociobiology 37:249-254.