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The elephant in the forest

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I know I've opened a column this way before, but as a biologist, I've found that canoe trips really do provide an excellent opportunity to explore and explain the outdoors. Especially those unseen leviathans that might be hiding in plain sight.

One morning, during a canoe trip in Ontario's Algonquin Park, my daughter Myles righted the canvas-wood canoe we'd turned upside down beside our campsite only to discover the numerous creatures that had taken fortuitous shelter beneath it. There were the usual slugs and spiders and centipedes, of course, but also a toad and, most unexpectedly — tight against a rib and blending with the varnished wood — a finger-length Eastern Red-backed Salamander.

"What were they all doing in there?" she asked later as we paddled toward the head of the lake and the day's first portage.

The answer was that they'd all crept in looking for food (i.e., each other) — or to get out of the rain that fell most of the night. This seemed too simple and uninteresting, however, so I'd also explained that it was a pretty good example of how animal species are passively moved around by bumming rides with unsuspecting humans. This kind of hitchhiking clearly doesn't make much difference when you're merely flashing a couple kilometres down the same lake, I'd finished, but if you're paddling, say, a large sea-going outrigger full of stowaway insects, lizards and rodents from island to island across the South Pacific, you'd surely be introducing alien critters where they'd never been and were sure to mess things up.

"Then how come they don't call people an invasive species?"

Her logic was brilliant, as usual, yet it wasn't the assisted-colonization potential of her discovery that intrigued her.

"I want to look for salamanders," Myles blurted as we landed where a sign announced the portage. This was partly because of the one she'd found earlier, but also out of recognizing that the wet forest-floor conditions at the pull-out were favourable for amphibians. I was also aware that, for practical purposes, "I want to look for salamanders" translated into "I want you to find me a salamander." Because I took my role as chief treasure-hunter seriously, I cast around for a likely spot, finding a tiny, overgrown stream sluicing in from the right.

"This looks like a good place for two-lined salamanders," I said, turning over a log about a half-metre from the water. And there, as if by decree, was a pencil thin two-lined. I had to suppress the urge to pump my fist.

Recognizable and instantly differentiated from its cousin Mr. Red-backed by the duller dorsal stripe; on closer examination the bar is split by darker mottling to create a two-lined effect. Two-lined salamanders also have a unique, bright-mustard belly that peters out onto the tail, which, along with the species' defensive predilection for wiggling and thrashing wildly — as it did while Myles juggled it from hand to hand — creates a distraction for a potential predator. Offered this soapbox for a salamander talk, I climbed right on.

Red-backed and two-lined salamanders both belong to the Plethodontidae. Though the name refers to an aspect of tooth morphology, this great pan-American salamander family's most defining characteristic is its lack of lungs — an ancient derived trait for living in streams that also bestowed an increased capacity for cutaneous (skin-wise) gas exchange in moist environments like forest floors. As often happens with evolution, acquiring this single respiration trick allowed for an amazing adaptive radiation over the past 50 million years: today's 400 species comprise 27 genera, the greatest diversity among any of the 10 salamander families and one of the broadest of any group of vertebrates. Plethodontids occur in the west from British Columbia to Brazil, and in the east from Labrador to Florida; the ones we'd found that day in Algonquin represented the two main thrusts of the group's eastern colonization — woodland salamanders and stream salamanders — both in the somewhat miniaturized versions which define them in the north. Though rarely observed (you could stand in the same spot in a forest for a thousand years surrounded by them and never see one), salamanders are often obscenely abundant, and in some mixed hardwood forests of Eastern North America make up the dominant vertebrate biomass.

"What's biomass?" Myles had asked, clearly fascinated with the ease of our find.

"It's a bit hard to picture," I explained, "but if you averaged all the vertebrate animals in a square kilometre of forest, say, in Maryland, you might come up with something like a half a deer; a quarter of a fox; a box of squirrels; a small heap of mice, voles and bats; a bucket of frogs and toads; a few lizards and snakes; a waist-high pile of birds — and a ton of salamanders."

"A ton as in weight?" she gasped, gazing around at the silent leaf litter as if an elephant were buried beneath it

"Or more."

In fact, the importance of salamanders in temperate forest nutrient cycling cannot be understated. Given their modest size and low metabolism, plethodontids, for instance, are able to feed on tiny insects too small for other terrestrial vertebrates (like frogs, some gather their prey with sticky projectile tongues), and so have carved out their own niche: they're perfectly adapted for the netherworld of leaf litter and gritty detritus, mossy talus and gooey seeps, dank caves and wet crevices, beneath bark and in rotted logs.

That heady information dump finally seemed to satisfy Myles, and we both watched as she released the two-lined back to the safety of the log, which it quickly wriggled under, soon to erase this bizarre abduction from its neurons. I may have maintained my status as chief treasure-hunter, but I'd also guaranteed that as we continued, Myles would never look at a forest floor in the same way.

Leslie Anthony is a Whistler-based author, editor, biologist and bon vivant who has never met a mountain he didn't like.

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