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The Pakaraima slender opossum, a new species named after the 500-metre high plateau in western Guyana that gives rise to Mount Ayanganna and other flat-topped mountains. (Francis X. Faigal)
The Pakaraima slender opossum, a new species named after the 500-metre high plateau in western Guyana that gives rise to Mount Ayanganna and other flat-topped mountains. (Francis X. Faigal)

How I discovered a new species of opossum, and why it matters Add to ...

In 1984, I followed in the footsteps of Randolph Peterson, ROM’s mammal curator at that time and my former zoology professor at the University of Toronto, by becoming a researcher of mammals, particularly bats, which were his specialty.

I have identified a total of seven new species (all bats) over the past two decades, a pretty good record for a mammalogist (entomologists have it easy by contrast – there are about one million known species of insects, but fewer than 6,000 mammals).

That first mountain expedition to Guyana was in 2002. But it would take a collaborative effort involving three other biologists and more than a decade of research to officially conclude the successful discovery of a new species of opossum.

Despite almost two centuries of progress, some aspects of biological fieldwork have not changed. GPS, satellite phones and planes have made exploration easier and safer, but, as I realized standing helplessly at the remote airstrip in Guyana, some places remain so isolated that hoofing it is the only way to get there.

Help from the indigenous people is indispensable, and luck is as critical as technology to a successful mission. Now I had no guides and no one to help me carry my gear to Mount Ayanganna.

But my luck soon turned. The guides told me that six other Amerindians from their village near the Brazilian border were panning for gold nearby. I persuaded the lead drudger to find them, and ask them to join our expedition.

Within 24 hours, we had all assembled under a makeshift plastic tarp crammed against the dense jungle tangle beside the airstrip. We would spend the next six weeks eating, sleeping and playing dominos together.

But I first had to negotiate with one of a group of itinerant gold miners from Brazil who had illegally sprung up near the airstrip. Putting aside my misgivings about their illicit and environmentally damaging activities, I made a deal with the devil: In a fractured mix of Portuguese, Spanish and English, I rented a boat to ferry us to the head of the trail to the summit of Mount Ayanganna, pioneered a year earlier by an American botanist.

As we finally sailed upriver the next day, the environmental damage caused by mining was all too apparent.

Big, rusty dredges were excavating the river bed for gold, leaving a deadly spew of silt and toxic mercury (used to extract the ore) in their wake.

Clearly, the area’s biological treasures needed to be catalogued before it was too late.

We reached the trailhead the next morning. Our first camp was just an three-hour, three-kilometre hike over what seemed like an endless mat of gnarly roots broken up with several creek crossings over “monkey bridges,” ridiculously slippery tree falls that made-up our meandering trail through the tropical rain forest.

It took the drudgers four days and six round-trips to carry all the supplies up from the river.

We started the biological survey by setting nets to catch bats, and traps for rodents and opossums.

The opossum is one of the minority of marsupials found in the Americas rather than in Australia. They live mainly in southern climes, but one species, the Virginia opossum, has been slowly moving north in Ontario, and is now common as far as Guelph.

It normally lives in the forest, but this omnivore has also adapted to urban environments and the cornucopia of food available in household garbage. Another species, the grey short-tailed opossum from South America, is an important model lab animal for immunological research related to human diseases.

After a week at the first camp, we ascended for three hours to our second base at an altitude of 1,100 metres. The weather was getting cooler and wetter.

On our first morning at the second camp, I noticed that the spring-loaded door had closed on a trap set the previous night, precariously perched on an angled tree trunk. Excitedly, I cracked open the door to peer inside.

A small opossum, with characteristically large eyes, was staring back at me.

However, it was impossible to tell precisely what species it was, because so few South American opossums have been caught and studied. I closed the door and cheerfully brought the trap, with opossum inside, back to camp.

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