365 million-year-old fossils & mating snakes

Jasper Fitzhugh – On Science
June 02, 2011
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When I was six, my Dad took my sister, mother and I on a fossil finding adventure in east Jasper National Park. Our mission had us bush-whacking through tick-infested juniper and winding up and down game trails. In the end, we were rewarded with the rise of great limestone walls laden with evidence of clams, sponges and other sea life that left their bodies to harden in the Devonian mud.

A few weeks ago, I re-visited this site with my family, including Dad, and my six-year-old son. We found it without too much trouble, making our way down a bluff to the exposed limestone walls below. Although it appeared some of the larger fossils had been removed, there were still many to wonder at.

My Dad was a boy when he found this site while fishing with his father. To him, it seems like a long time ago, but in geologic time six decades barely register.

About 365 million years ago, most of what is now North America was covered by a shallow, tropical sea. Over time, tiny sea creatures deposited their calcium rich shells on a seabed that would later turn to limestone. Like a great area rug buckling and folding on a hardwood floor, tectonic pressure thrust up these ancient sea beds and they became mountains. The exposed limestone of these mountains have allowed paleontologists access to fossils that have helped establish a chronology of how life evolved on earth. For example, in 2006, near the area I stood with my family, Cambridge scientists discovered microscopic teeth belonging to an ancient relative of the snail family. This was the oldest fossil find of its kind on record.

Running your finger over something millions of years old gives you perspective. Before dinosaurs, before mammals, and at a time when life on land was just beginning, these creatures existed on an earth quite different from ours. As I turned chalky fossils over in my hand, I imagined a world with nothing but wind and waves to break the silence.

So fixated were we all on the evidence of the past, that it took us a few moments to realize something equally riveting was happening in the present. A snake rustled by in the dry grass only centimetres from our toes, its smooth grey back shining metallic in the sun. I can name only a handful of times I have seen a snake in this park, and so I’ll admit that I was less than calm, chasing it along desperately trying to get a picture. My sister called me off before I got too far, but I had a good enough look to know it was a wandering garter snake.

There are two snake species in Jasper, the wandering garter and the red-sided garter – the latter being easy to differentiate because of the red colouring on its head and sides. The wandering garter can appear grey, to olive-green to brown, and some have a pale stripe down their sides. The underside of the head is usually white. The one we spotted was an adult, about 50-60 cm long. Adults average from 45-107 cm, while the young (born in August) average 17-23 cm. Although they spend the winter conserving heat together in a communal den called a hibernaculum, it is most common to see snakes on their own.

And that is why we were incredibly surprised when, a few meters away, we saw three more snakes wrapped around one another at the base of a dry, gnarly bush. They were mating. The smaller males wound around the larger female as the mass of them wove their slender bodies through the tangle of branches. Females omit a strong pheromone to attract males, and it is not uncommon to see many males trying to mate the same female. In some places, female garter snakes attract enough males to form a writhing “breeding ball” that can be composed of 20 to 30 males hoping to mate her. This scenario is less likely in Jasper where garter snake populations are more scattered, and we were fortunate to see a snake at all.

I tried coaxing my son closer to watch, but he wasn’t keen to join me. Maybe he still experiences an innate aversion to snake-like things, evolved in humans from millennia of lethal bites. He need not worry about the wandering garter though – The mildly neurotoxic venom of these little guys does not affect humans. It helps only to subdue their small prey, which can include amphibians, fish, invertebrates, rodents, small birds, and carrion. They rarely bite anyway – they are usually too busy trying to get away.

With dinner guests due shortly at my parent’s house, we eventually had to rip ourselves away from snake watching and head home. It was hard to leave knowing how unlikely it was that we would witness the same thing again in our lifetime. As we hiked back along the trail, we spotted our first clump of this year’s crocuses. It was the kind of rare day you feel cannot get any better. The kind of day you remember for a long time, much like the day I spent here with my Dad when I was little.