Attack of the clones…

Trembling AspenOne of the things I love most about my job is seeing the sparkle of wonder that lights in a person’s eye when they discover something amazing about an object they see everyday.  There’s nothing quite like watching people suddenly see the world in a whole new light.

Trembling aspen are one of those amazing everyday things. They’re a ubiquitous tree, found in all Canadian provinces and with a range stretching south along the Rockies as far as Mexico.  Where I live on the border of the boreal forest and aspen parkland, these often spindly, pale poles are everywhere, making up the bulk of smaller forest patches and bringing a welcome contrast to the dark green of the spruces and firs.

To most people, they’re unremarkable, row upon row of white-grey trunks, stark against the winter’s snow, often blending into the background. To me, however, they’re the above-ground manifestation of a complex and sometimes enormous network.

Trembling aspen are clonal. Although they can produce seeds, they very rarely germinate and most of their propagation is achieved through roots shooting up new trees and colonizing open areas. An entire woodlot can be made up of one genetic individual, all connected by the same set of roots. The easiest way to spot a clonal colony is in the early spring or fall. Look for that group of trees that have leafed out or turned yellow before all the rest. That’s all one individual. In fact, the heaviest living organism in the world (weighing in at an estimated 6000 tons) is an aspen clone in Utah named Pando (The Trembling Giant).

Aspen have likely evolved this form of reproduction as a way of dealing with fires, which is the main force driving the dynamics of the boreal forest and the parkland to the south. Aspen, or white poplar as they are sometimes called, are excellent colonizers. Around here, they’re the first tree to re-establish after a fire. Most blazes that rip through a forest don’t burn at an overly hot temperature and while they kill off the most of the vegetation on the surface, they usually leave the roots intact. Once the fire has passed, the aspen roots are instrumental in stabilizing the remaining soil and fixing raw nutrients, like nitrogen, so that it can then be used by other organisms.

This regular disturbance by fire is actually very important for the long-term viability of an aspen clone. Each individual tree (ramet) isn’t particularly long-lived, and usually die back after about 200 years. Fire cleans out the dead wood. It also kills back shade-tolerant species like white spruce and balsam fir that would ultimately take over the forest through succession, beating back the aspen.

Being part of a clone definitely has its advantages. With all the trees connected, they can take advantage of localized resources, such as water and nutrients, moving them from rich areas throughout the entire clone so all the trees can survive.

One might think that with the ability to produce infinite copies of oneself, an aspen clone could live forever. In theory, I suppose it would be possible. Although a 200 year life-span for each individual ramet isn’t especially long in the world of trees, a clone can live for thousands of years. In fact, that clone in Utah is estimated to be over 80,000 years old. However, a recent study done in San Diego has shown that as clones get older, their ability to produce pollen and thus reproduce sexually, eventually disappears as a result of a build up of genetic mutations over millennia. Without the ability to produce viable seeds, the clone becomes vulnerable. If disease or succession or an especially hot fire were to wipe out the clone, it would have been unable to create a new generation before succumbing.

Still, considering some aspen clones have been around since before North America saw its first humans, I’d say they’re doing fairly well with their current life history strategy. Every time I wander among their ghostly pillars, I can’t help but wonder at all they’ve seen. If only trees could talk…

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Brainy Birds

Common Raven - Corvus coraxWhile they make their home in the north woods all year round, I tend to notice ravens more in the winter. Without the distraction of countless other species vying for my attention, I’m drawn to the stark beauty of their black wings against the blue sky of a winter’s day.

We also have more of them this time of year. It’s not uncommon to see over a hundred in a day as those who were breeding further north make the trip south to my neck of the woods to join their brethren scavenging for food among the ice and snow.

Out on Lake Winnipeg, they tend to follow the commercial fishermen, descending in the dozens onto the ice after the men move off, cleaning up the leftovers before the wolves and foxes get there.

Ravens have had a pretty bad reputation throughout much of history.  Feared as harbingers of ill omen, ghosts of the murdered, or souls of the damned, ravens have haunted literature from ancient myths, right up to Poe and Steven King. Still, not all feared this big black bird. Some cultures, especially North American first nations, revere the raven as a creator and trickster.

The species comes by this last attribute honestly. For a bird brain, ravens are very intelligent, having one of the largest lumps of grey matter of any avian species. For starters, they have an excellent memory, a skill that comes in handy when having to rely on stashes of food to get through the winter. Ravens and other members of the corvid family hide extra food, when it’s in abundance, in caches (i.e. under a rock, wedged in a tree, etc.). It gives them something to get them through the leaner times. If they were a dog, they would sniff out the food later, but unlike mammals, ravens, like most birds, don’t have much of a sense of smell. So to find their caches, they have to remember where they put it.

Ravens take it one step further, not only remembering the location of their caches, but keeping an eye on their flock mates in case there’s the opportunity to lift somebody else’s food.  This risk of losing your stash to a neighbour has resulted in ravens demonstrating the ability to deceive, going through the motions of hiding a cache, but leaving nothing behind, a fascinating display of insight.

Having a good memory opens the door for all sorts of learning. Ravens are good mimics. My mom told me a story of a raven they had at the zoo in Winnipeg who had learned to talk, mimicking the patrons just like a parrot.

Probably the most useful expansion on a good memory is the ability to use trial and error to learn new things. A number of studies on raven cognitive abilities have demonstrated this talent. Birds have been shown to use tools and solve complex problems to obtain food, even working together towards a goal, like tag-teaming a dog, one distracting him from his bowl, while one of the birds eats, then switching roles.

However, the manifestation of their awareness and intelligence that fascinates me the most, is their penchant for play.  Ravens, especially the young ones, like to have fun, sliding down snowbanks and kicking snow onto unsuspecting passersby from their perch high up on a building. Many times I’ve watched, transfixed, as a pair of them raced after each other through the sky, whirling around before locking talons in mid-air and barrel-rolling among the clouds.

On other occasions I’ve been lucky enough to spark one’s interest. One quiet winter evening, I called out to one, mimicking the soft caw that seems to be a contact call. Usually they ignore me, but this one didn’t, coming closer and landing in a nearby tree, echoing my calls. As we chirped and croaked back and forth to each other, he cocked his head and I couldn’t help but get the feeling that we were both wondering what the other was thinking.

Can you hear me now?

Close up of a Great Gray OwlSomehow I’ve managed to make a good part of my living for the last decade standing around in the dark. Owls have been a source of fascination and a subject of study for me for quite a while now.  I’m not alone in that fascination. Many people are drawn to their seemingly all-knowing eyes and wise faces.

I hate to destroy any long-held beliefs, but owls aren’t really all that wise. There are many bird species (the crow family, for example) that have much greater levels of intellect.

That doesn’t mean owls are any less remarkable. This group of birds has evolved some amazing adaptations to help them make the most of their nocturnal realm.

What I find most fascinating is their ability to hear in three-dimensions. While we can perceive depth with our eyes, they can also do it with their ears.

Owl Skull (without sclerotic ring) showing ear openings.

The secret is asymmetrical ear openings. In most animals (ourselves included), the ears tend to be at approximately the same level on either side of the head. However, in the especially nocturnal owl species or ones that predominantly use hearing to locate their prey, one ear is usually higher than the other.

As a result, sounds do not reach both ears at the same time. It’s this delay that allows the bird to figure out where the sound is coming from.  They can be quite precise, detecting differences in timing up to 30 millionths of a second. When an owl hears a sound, the medulla of the brain creates a three-dimensional mental map of where it’s located. They then hone in on that point by moving their heads until both ears are hearing the sound at the same time. When they reach that point, they are facing their prey. Adjustments can be made while in flight, moving their heads until they’re lined up to strike.

Because they are operating at such a high level of precision, it’s important to have the best hearing as possible. In many owls, like this Great Gray Owl above, most of their face is made up of a disk of feathers. This facial disk acts like a satellite dish, funneling sound to the ears. Muscles under the skin allow them to adjust the shape of the disk as needed to get the best reception. Cup your hands around your ears and you’ll get an idea of how it works.

The size of this disk of feathers is a pretty good way to quickly assess just how nocturnal an owl species is. Larger disks, relative to the overall size of the face (like in Boreal Owls or Barred Owls), means that the species tends to hunt mostly at night.

Great Grays are a bit of an exception.  They have huge facial disks, but hunt mainly at dawn and dusk. These owls, however, hunt prey that are hidden by layers of snow in the winter. Like hunting in the dark, they can use their ears to pinpoint a vole running under the snow up to 150 metres away! It gives a whole new meaning to good reception.