Tag / colour

by Roslyn

Peacocking on Parliament Hill

Here’s my poster from the Evolution conference in Ottawa:

Evolution poster

The colours are a bit off in this shrunken version, but you can download a larger PDF version here. The poster covers some of my work on the lesser-known green peacock (a close relative of the familiar blue variety). Green and blue peafowl have markedly different body colours, and in the green species, the females are as colourful as the males. Interestingly, the two species have eyespot feathers that are nearly identical. Why are their eyespots so similar? I think it’s because these feathers are crucial for courtship, and females of the two species have similar taste.

One of the main results I’ve found is that despite appearances, there are subtle differences in the eyespot colours of the two species. These differences, while slight, might be readily apparent to birds since they have excellent colour vision. I think the differences are the result of adaptation to different light conditions. Blue peacocks live in India, and prefer bright, open habitat like riverbeds and agricultural fields. Green peacocks live in darker forested areas of Southeast Asia, and their eyespots may be slightly brighter and greener to take advantage of dim forest light.

It was my first Evolution conference, and I hope I can get to another. The talks were fantastic. Author David Quammen summed things up nicely in his public lecture: “Science is people.” This theme carried through the meeting, from Rosie Redfield’s tale of the pitfalls of falling in love with your hypothesis to a rally where scientists young and old marched together on Parliament Hill (see my pictures here). How often does that happen?

by Roslyn

Life imitates [filmmaking] art

Congratulations to Myra Burrell – her peacockumentary has been short-listed for the Animal Behavior Society’s film festival!

Myra, a veteran of the natural history film program at the University of Otago in New Zealand, traveled to California with me in 2010. She helped with peacock field work, capturing more females than anyone thought possible. Somehow, in the meantime, she made a movie about the birds. It’s a short film that gives you an idea about what happens on a peacock lek, from the hen’s point of view.

It’s quite an honour to be among the 6 films selected for festival screening, since they must get on the order of ~100 applicants. If Myra wins, it would be oddly fitting: a wildlife film straight out of a park that moonlights as a real Hollywood set.

You can watch “Hen’s Quest” here.

The best parts? I love the music and Myra’s cinematography. I contributed writing (including the title!) and did the artwork; Brian McGirr turned my map drawing into a fantastic animation. Good luck, Myra!

by Roslyn

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.

by Roslyn

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.

Continue reading →

by Roslyn

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.

Continue reading →

by Roslyn

Super indelible flower colours

How do you fire a pollinator?

That was the question in last week’s Ecology, Evolution and Behaviour departmental seminar. The speaker was James Thomson, an evolutionary ecologist from the University of Toronto who specializes in the interactions between plants and their animal pollinators. His research shows that nectar-addled hummingbirds are like corporate ladder climbers. Bees, on the other hand, are always getting canned.

Pollination syndromes have been a major focus of Thomson’s work1. These are not garden ailments. “Syndrome” here refers to a suite of traits that tend to be found together, in this case because they help a plant attract a certain kind of pollinator.

Bird-pollinated flowers tend to be red and tube-shaped, producing lots of nectar but relatively little scent. Birds have sharp vision, and do not depend much on their sense of smell. Honeysuckle is an example of this type of flower – or anything that looks like a hummingbird feeder. Bee-pollinated flowers come in shades of yellow, blue, and purple, because bees cannot see the colour red. Familiar examples are sunflowers, snapdragons and wild pansies. These often have petals modified into special bee landing platforms. Flowers that specialize on birds and bees are common, but there are many other pollination syndromes. If a flower is orange-brown and smells like rot, it probably depends on carrion flies. Mammal-pollinated flowers often smell fruity, like synthetic grape flavouring.

In his talk, James Thomson reviewed a decade’s worth of work on beardtongue flowers from the genus Penstemon2. In 2007, Thomson and his collaborators used genetic analyses to build the evolutionary tree for close to 200 of the species in this group3. When flower traits were mapped on to the Penstemon family tree, interesting patterns were revealed.

First, the bird and bee pollinated species were distributed broadly throughout, implying frequent transitions between these two syndromes in the history of the Penstemon group. Like an evolutionary magnet, pollination by one type of animal or another exerts a strong pull on multiple flower traits in concert. Evolving species are drawn rapidly towards a new form, so you almost never find intermediates.

This lability or changeable nature of floral traits was not much of a surprise, but the Penstemon tree also suggested something incredible. Floral evolution was directional.

Continue reading →