A Nocturnal Excursion with Riparian Entertainments

Our expedition clients have spent the last three nights hiking the trails around the field station here in the Peruvian rainforest. Those nights have been very productive, in terms of herps and other critters seen and experienced. But long hikes in the heat and humidity take their toll, and afterwards, when folks close their eyes for sleep, the afterimages of waving flashlight beams play against the back of their eyelids.

It’s time to change things up – time to take a night off, give tired eyes and legs a rest. Time for the Boa Boat. The sign-up sheet is over by the icebox, and we leave a half hour after dark. Wear long sleeves, bring your bug spray and rain gear, and -don’t- wear your rubber boots – if the boat should capsize, they’ll fill with water and pull you down quick to the bottom of the river. Not a pleasant thought but let’s be safe out there.

We take out the skiff for these after-dark adventures. The Shiripira holds six or seven passengers, plus the boat driver. Usually it’s the field station caretaker Julio running the boat, and he’s the right person for the job. Julio knows the river, knows all the details and landmarks during the day or in the dark. And he knows the rhythm and flow of the Boa Boat cruise, and is good at bringing the boat back around to double-check on potential creatures. We do a lot of bringing the boat back around on these excursions.

For you first-timers, here’s how it works. As the boat chugs down the river, we shine our flashlights at the trees and bushes along the bank. We’re not necessarily looking for critters – we’re looking for eyeshine. If we see some eyes reflecting back at us, we’ll take the boat in for a closer look.

Eyeshine can come from a lot of different animals – even spiders and moths. But spider-shine is usually a pale green, and you quickly learn to ignore those tiny points of sparkling light. What we’re looking for is red or reddish orange eyeshine. Those eyes could belong to a boa, an Amazon Tree Boa (Corallus hortulanus) to be exact. They are up there in the salad, some close to the water, some higher up, and they’re all awake and hoping to snag a tired bird, a sleeping lizard, or some branch-running rodent.

Adding to the challenge. reflecting red eyes could also belong to a bird. Parauques and Potoos like to hang out and roost along the river, and many times eyeshine belongs to one or the other. Keep your eyes on the shine because if we’re lucky, the bird will blink or swivel its head before we go all the way in to check it out. We’re hoping for things that don’t blink.

When you do spot some eyeshine, sing out loud enough for us to hear you, and waggle your flashlight around the area. One of us leaders will use a laser pointer to circle the spot for Julio, and he’ll bring the boat around for another pass.

Oh yeah, we also need you to keep an eye on the water, especially near the banks. We might get eyeshine from a crocodilian, usually a Spectacled Caiman but sometimes a Smooth-fronted Caiman. And sometimes we see other things swimming in the water.

The group settles into a routine within fifteen minutes or so, after a few false alarms over green-eyed spiders and red-eyed moths. Each person shines the shoreline closest to them, roughly dividing the boat in half. Everyone is concentrating hard on spotting something interesting. Tubes of light swing across the dark river, sometimes highlighting bats on the wing, or birds disturbed by our approach. Eventually, someone locks onto eyeshine that doesn’t blink or fly away on two wings. A cry goes up, flashlights and laser pointers wiggle, and Julio brings it around town.

The first boa is an exciting moment followed by “NOW what do we do?” If it’s low enough to grab, Julio will bring the boat right underneath, sometimes crashing into low-lying bushes and trees along the bank, so everyone stays alert and tries to keep twigs and branches away from faces.

Once in a while we can simply reach up and get the snake, sometimes we need to use snake tongs or a fishnet to extend our reach, and occasionally we can shake the serpent loose. Sometimes, all we can do is put a flashlight beam on the out-of-reach snake and just enjoy the moment.

Once the snake is in the boat, time slows back down to normal speed, and everyone new to this experience has a moment with their first Amazon Tree Boa.

ATBs are highly variable in color and pattern, so we will keep looking for more. The brightly patterned juveniles are desirable, and hopefully we’ll see one.

On a successful night, we will bag and bring back an adult and a juvenile boa for photo sessions at the field station. Some are examined and left where we found them. The snakes we bring to camp go back out to the river the next night, and are returned to the point of capture. How do we know where they go? Julio of course, who has yet another superpower – he knows exactly where we found them.

By now we’ve settled into a routine and the passengers start to take stock of their situation. It’s pleasantly cool out on the river at night, and with a life jacket tucked underneath your bottom, the boat is a comfortable place. Quite a welcome change from sweaty treks along trails, where the forest holds the heat and humidity all too well.

Red eyes in the water near the bank also demand attention. The larger the eyes and the farther apart they are, the larger the caiman, and while we want to see any and all crocodilians, there’s a sensible size limit as to what we might catch by hand. It may not be obvious, but a four foot Spectacled Caiman is an entirely different creature than a four foot Alligator from back in the States. Gators are pussycats by comparison.

We’ll try for every caiman we see, shushing everyone as we make our approach. Caimans can be wary, but sometimes the boat slides right in on them, and a quick grab can be made from the front of the boat. How do you grab a caiman? After determining that it’s small enough, you want to get it around the neck with your thumb and fingers. This can be an intimidating idea, which is why an eight inch baby is a good starter caiman.

Small caiman are easily passed around the boat, giving many people their first physical contact with a crocodilian. I always enjoy witnessing this experience, as it can be a holy-shit moment of realization for some of our clients – there they are, in the dark, thousands of miles from home, on a small boat on a small river somewhere, and with a crocodilian in their hands. It’s fun to watch, and it feels great to have a part in making it happen.

The most common finds are Spectacled Caiman (Caiman crocodilus). We see Smooth-fronted Caiman (Paleosuchus trigonatus) on occasion, but we have better luck finding them in small streams inside the forest. The rarest find is the Black Caiman (Melanosuchus niger), which are usually hunted out on rivers close to villages and fishermen. I’ve been lucky to see a handful, and once plucked a juvenile right out of the water, much to the surprise of us both.

Another thing we watch for is snakes swimming in the water, and we’ve encountered a number of species, including Anacondas (Eunectes murinus). Getting an anaconda in the boat can be a challenge, if they have any size to them.

Sometimes the snakes wiggling in the water are somewhat small, and it makes me think they are taking a real chance – there are plenty of big fish in that dark water who could take them down.

Often as we’re chugging downstream, we hear the deep croaking of a solitary frog along the bank, and sometimes we spot them, usually by eyeshine. They are Gladiator Treefrogs (Boana boans), so called because breeding males often grapple with each other over nesting areas. These are among the largest treefrogs in the Amazon Basin, with males reaching a snout-to-vent length of five inches. We sometimes see them elsewhere, but the river boat ride is a great place to encounter a frog that will cover most of your hand.

When we’re done hunting boas and grabbing caiman, we have one more surprise in store, as Julio turns off the main river into a small channel leading to an oxbow lake.

The still waters in the oxbow allow aquatic and semi-aquatic plants to collect into dense mats here and there, and Julio points the skiff directly at a large floating raft of vegetation. He cuts the engine and the Shiripira slides into the mass and slows to a stop.

On either sides of the boat is a collection of grasses, water hyacinth, parrot feather, and other greenery. People play their lights over the vegetation and as they focus, living creatures come into view. “Frog!” someone calls out. Others join in. “There’s one on this side too, and it’s calling!”

Frogs are commonly found on these floating rafts, and some are species that we will not see walking trails in the rainforest. Sliding the skiff into the mass of plants in the dark is an unexpected adventure, one that adds species to the trip list, and provides a chance for observation and photos from just a few inches away.

It’s not all frogs, either – there are slugs and snails, grasshoppers and spiders, and the occasional aquatic snake, all visible at close quarters. These floating mats are everywhere in Amazonia, and the overall biomass of animals making a living on them, in them, and under them, must be immense.

It gets quieter as the passengers fall deeper into the small stories taking place a few inches away, and the sounds of the night take over – the hums, chirps and trills of insects, the whistles and peeps of frogs, the faint clicks of bats fluttering unseen above the boat. Overhead the night sky is a starry spectacle, as good as it gets in these times of widespread light pollution. This is the point in every excursion where we turn off every light, and drink in the scene above us for a few minutes.

And then it’s time to back the boat out into the channel and turn around. It’s an hour’s journey upstream to the field station, and while there may be more for us to see, there’s a sense of relaxed contentment among the passengers now, replacing the alertness and anticipation marking the downstream leg.

Tomorrow night the gang will be back on the trails, perhaps with a bit more spring in their step. The Boa Boat provides the opportunity to rest and recharge, while still enjoying a singular adventure in Amazonia. Except for me, Christoph, and Julio – we have a Bird Boat to manage, at first light in about five hours….

Thanks for reading this.