Tag Archive | Rewa River

Drifting on the Rewa

To get back to my posting on the trip to Guyana I made this spring, I should get some of the most charismatic megafauna out of the way.

But before I get into that, please consider filling out this science blog reader’s survey being done in conjunction with Science Borealis, designed by Paige Jarreau. The official blurb is here:

I’ve teamed up with Science Borealis, Dr. Paige Jarreau from Louisiana State University and 20 other Canadian science bloggers, to conduct a broad survey of Canadian science blog readers. Together we are trying to find out who reads science blogs in Canada, where they come from, whether Canadian-specific content is important to them and where they go for trustworthy, accurate science news and information. Your feedback will also help me learn more about my own blog readers.

It only take 5 minutes to complete the survey. Begin here: http://bit.ly/ScienceBorealisSurvey

If you complete the survey you will be entered to win one of eleven prizes! A $50 Chapters Gift Card, a $20 surprise gift card, 3 Science Borealis T-shirts and 6 Surprise Gifts! PLUS everyone who completes the survey will receive a free hi-resolution science photograph from Paige’s Photography!

OK! Are you still with me? Let’s talk about drifting on the Rewa! When we reached our highest-upstream camp on the Rewa, Josey, Brian and Rambo took Jonathan and I out “drifting” several times, basically motoring upstream a few kilcks and then drifting and paddling the boat downstream, in the hopes of seeing wildlife that would otherwise be scared by the motor. We did this several times, most often in the evening to get views of all the animals that come to the river to bathe or drink.

Using the drifting technique, we were able to see several family groups a capybaras, a species I had not previously seen in daylight!

The boat was not as quiet as a canoe, but after days of motoring on the river, this was pretty nice!

The capybaras were often accompanied by large horseflies. Surprisingly, none of these flew over to us, even when their hosts slipped into the river.

The capybaras take to the river when disturbed, and can even navigate extremely fast currents. I remember many times at Parare in French Guiana being startled by big capybaras splashing into the fast-flowing Arataye. This stretch of river was much more sedate, so allowed us to see the animals swimming quite well.

As usual, some of teh capybaras has things perched on them. This is a giant cowbird, which feeds on ectoparasites on the large rodent. Even Black Caracaras do this, but we did not see one doing so.

Drifting quietly also allowed us to spy wildlife we might have missed from going to fast: this iguana was well-concealed at most angles.

We also saw a number of tapirs, which often come to water to bathe in the morning an evening. These are the largest of the South American ungulates, and are very impressive see!

The tapir is a very shy creature in the wild, probably because they are hunted by anybody who can kill them! Unlike capybaras, which breed rapidly, tapir are one of the many species that quickly drop in population with even moderate hunting.

Here was a female tapir we saw at noon, not drifting. I did not get a shot of it, but she had big wounds in her flank, likely from a jaguar or puma. Rather than a relaxing bath, this poor tapir was likely hiding from a predator in the water.

This is what a tapir looks like shaking off!

They look much more elegant when their snout isn’t flapping madly!

Gorgeous animals! We felt really lucky to be able to see so many of these shy and magnificent creatures!

Guyana: the other archosaurs

May23

On my trip to Guyana, I was not only on the lookout for birds, but also their relatives, the crocodilians. Guyana is home to 4 species of caiman, including the largest and smallest species in the world.

On the Rupununi and the lower Rewa, I was amazed at how many black caiman there were. Paleosuchus niger is the largest caiman, and in my mind I still thought of them as very rare. Conservation efforts and a reduction of hunting have caused a definite improvement for this beautiful species across their range.

These large caiman can be dangerous, so while in their territory we made sure to bathe in shallow water where we could see them coming. With predators such as this, you are probably safe if you do not enter a good ambush zone, such as a place with a steep dropoff.

Rambo holds a baby black caiman, which we found in an aggregation near our camp one night. In Rambo’s hometown, Yupukari, there is a conservation and research outfit called Caiman House where the locals participate in monitoring and study of black caiman. Rambo has experience capturing, tracking and nest monitoring these impressive animals.

Jonathan posing with a beautiful little caiman. The babies tend to stick to protected “nursery” areas, as they are easy prey for birds and large fish.

If you want a juvenile caiman to open its jaws, a little tickle on both sides of the base of the lower mandible will produce this posture.

Above the major rapids, the Rewa is devoid of black caiman, and instead spectacled caiman and dwarf caiman abound. Here is a Schneider’s dwarf caiman cruising by our camp. I had seen Cuvier’s dwarf caiman in French Guiana (small ones living in small fast creeks), but seeing the adult Schneider’s was a revelation. These guys get fairly large, and inhabit even slow-moving sections of the river.

Brian tossed a piranha piece at this dwarf caiman, and it seemed to know exactly what was going on. It has probably seen several fishing groups upriver and has learned that when a boat pulls in, fish pieces from cleaning are often tossed out. This one had some fishing line attached, so we could try to haul the beast into shallower water. By the time the caiman got it’s feet planted, any further movement of the caiman was impossible!

All of the crocodilians we met were quite shy, and even large black caiman would flee if we caught them in shallow water. This dwarf caiman was willing to come for tossed fish, but not if we were too close to the water’s edge.

Some of the bolder caiman would stay on the bank as our boat passed, but most of them would flee for deep water.

If you go out in the woods in the tropics, be sure to look out for the local crocodilians! They are fascinating and beautiful animals.

We eat fish

Apr21

On an Amazonian river, the birds and mammals are impressive, but there is also a huge amount of nutrient cycling in the water. These rivers cover vast areas of forest where huge amounts of protein become available during the wet season. Because of this, the predatory animals along the river are very often piscivorous, feeding on fishes occasionally or exclusively. This post is a brief photo introduction to a few of the fish-eating animals commonly seen along these rivers.

Fishing spiders (Pisauridae) were best photographed at night, as during the day they are extremely skittish and quick to hide. We did not see any giant examples, as I had in French Guiana, but I did not make a concerted search either.

The Green Kingfisher (Chloroceryle americana) is an impressive kingfisher species also found in the Southern USA

The related Amazon Kingfisher (Chloroceryle amazona), by contrast is even more robust and has a much larger bill.

The White-necked Heron, Ardea cocoi, is the Amazonian equivalent to the Great Blue Heron. We saw a great many of these. They would often fly in front of the boat for may hundreds of metres.

The Sunbittern (Eurypyga helias), despite its name, is not a bittern at all, but rather related to the gallinules.

Here is a juvenile Rufescent Tiger Heron (Tigrisoma lineatum), one of the more magnificent of the Tiger Herons.

The adult Rufescent Tiger Heron is a gem.

Something familiar…Sort of. This is a Neotropical Cormorant (Phalacrocorax brasilianus).

This one I remember from Florida. The Anhinga (Anhinga anhinga), or snakebird is like a cormorant which swims with its body submerged. Interestingly enough they also soar on thermals!

Osprey down here are all migrants from elsewhere.

Giant River Otters (Pteronura brasiliensis) were abundant along the Rewa, always travelling in groups. They cooperatively hunt for large fish and caiman, and have some real mustelid attitude!

Giant otter snacking on a fish.

In addition to these avian, arachnid and mustelid predators, we also had to be predators in order to eat during the trip. I dislike catching fish for sport, but when it became clear that there was no other protein along for the ride, we turned to fish with gusto. The fish along the Rewa are diverse and abundant, and can be reliably caught with simple equipment. Under sustained commercial fishing, the larger fish would likely be wiped out completely, but since the Rewa has so few visitors, there are large stocks of big fish available. Catching fish in the dry season is especially easy, as all the fish which ordinarily would be foraging in vast areas of flooded forest are concentrated in the river.

This black piranha will be our evening meal.

Catch of the day: some peacock bass and something we will use as bait tomorrow.

Peacock bass, grilled.

Josy with the “vampire fish” or Payara, Hydrolycus scomberoides

The long fangs of these fish are quite impressive, fitting into slots in the upper jaw.

With direct flash, the fish looks even more scary!

Nonetheless, the payara is good eating. We also used the head for a special project! Stay tuned for the next post!

We did all our fishing with handlines, baited usually with pieces of small piranha. Here Brian and Rambo fish for tiger catfish

Here I am with a tiger catfish, genus Pseudoplatystoma. This is a great fish for eating, and two of these fed us for 3.5 days. Photo by Jonathan Meiburg.

The tiger catfish are absolutely gorgeous.

Further upriver, we caught some aimara (Hoplias aimara), which I was familiar with from working in French Guiana.

Brian and Jonathan with a big aimara. Jonathan is wearing Catherine’s home-made tubular headwear as protection from the sun, and maybe so this fish’s relatives don’t recognize him. All aimara claims for damages should be made to Jonathan’s record label, Sub Pop Records.

The day’s catch, with some to be dried to take home to Yupukari.

Aimara drying in the sun.

Stingless bees taking some of the aimara. Unlike other bees, meliponines feed scavenged meat to their larvae. Bees eat fish too!