Amazon: Animal a-listers

You know how it is. It's the last day of a fabulous trip, and you're on your way back to civilisation. I'd just spent the week knee-deep in mud, swatting at unknown biting things, half lost in the Cuyabeno Wildlife Reserve, a World Heritage Site in a remote part of the Ecuadorian Amazon. I'd earned the relaxing boat ride home, winding past giant kapok trees and overhanging acacias.

Warmed by the morning sun, I dozed amid the soporific whine of cicadas. Suddenly the outboard motor thrummed. The boat swerved, throwing me across the bow.

"Mira!" exclaimed the boat driver, pointing at the lush riverbank.

"It's an anaconda!" yelled my guide.

My heart leapt — I've been roaming the Amazon rainforest for more than 20 years, but hardly ever seen the world's biggest snake in the wild.

As the boat drew closer, I could make out its massive coils draped like a giant rope over a fallen tree trunk. Its body was as thick as my thigh. The wedge-shaped head, as big as a rugby ball, poked out from the centre of the coils.

This moment was truly special — seeing an anaconda in the Amazon is like spotting one of Africa's Big Five on safari. But the Amazon's equivalents are far more elusive. You're very lucky if you catch a glimpse of any of its biggest inhabitants: the anaconda, jaguar, giant anteater, tapir and Amazonian manatee. They're hard to spot given their solitary, cautious habits and the dense vegetation. What's more, hunting and habitat destruction have led to extinctions close to towns and villages.

Even in pristine rainforest, you're likely to find only signs of these large animals — marks on a tree trunk where a jaguar sharpened its claws, or a termite's nest ripped open by the anteater's powerful forelimbs.

However, if the Big Five have eluded you, here's an alternative quintet of Amazonian creatures to search for:

Pink dolphin: This near-blind freshwater cetacean uses its precise sonar to navigate the murky waters. You often spot small groups, typically at the confluence of two rivers, where fish abound.

Black caiman: This is the biggest reptile in the Americas and the Amazon's largest predator (up to 20 feet long). You'll find caiman at night when your torch beam reflects off their eyes as your boat motors alongside a riverbank.

Monkeys: Given that the Amazon is a primate biodiversity hotspot, you're almost guaranteed to see squirrel monkeys, spider monkeys or saki monkeys cavorting among the riverside vegetation during any boat ride.

Turtles: Most Amazon turtles belong to the ancient side-necked group, which retract their heads sideways, instead of straight back. Turtles prefer quiet lagoons or slow-moving rivers, often basking in small groups on protruding branches.

Poison dart frog: Though some of these frogs could fit on a penny, their showy colours warn predators not to make a meal of them. Their skin contains among the most toxic poisons in the animal kingdom. There are over 175 species, but their tiny size makes them quite difficult to spot.

How to do it: Nomad Trek offers a four-day tour to Ecuador's Cuyabeno Wildlife Reserve staying at Tapir Lodge, priced from $649 (£425) per person, not including flights. From Quito, travel by road or plane to Lago Agrio, where the tour departs by boat into the national park. The two-hour ride down the Cuyabeno River is ideal for monkey spotting.

Read more in the December 2015 issue of National Geographic Traveller (UK)