Observations about Our Study of Pink River Dolphins in Pacaya Samiria National Reserve

by Captain Bill

Observations about Our Study of Pink River Dolphins in Pacaya Samiria National Reserve

Late in the afternoon on February 13th we tied up at the confluence of the Pacaya and Amazon Rivers. Dave and Dottie Bonnett already had the acoustical equipment ready. Pink and Gray Dolphins were nearly always breaching. Within minutes of turning the engines off Dave had the hydrophone in the water experimenting with depth, calling out instructions to Dottie to log into the records. Dave put on the headphones, turned the digital recorder on and excitedly called out, “We have communication! Ohh, the clicks. The chirps. What was that? It sounded like a fog horn. Did one just blow? Dottie write that down. Get the time. That was no catfish! Shirley, did you see it? Pink or Gray? Dottie write that down. Now it sounds like popcorn popping…”

That recording was exciting, the equipment worked, the technique was good, the boat was quiet, but what we wanted we could find only far inside Pacaya Samiria National Reserve. Strange as it may sound for a scientist wanting to study Pink River Dolphin communication, there were too many dolphins at this location. Dave wanted only Pink River Dolphins (Inia geffrensis), with no Gray River Dolphins mixed in. He wanted no background motor noises or even the sound of paddling a canoe. Here, subsistence fishermen worked with the dolphins to net their family’s supper. Still, it was our first recording, and we were happy.

Early the next morning we officially entered the reserve to begin our scientific study. This was a hawk day. Some days are sloth days. This was a hawk day. We were amazed at the number of species of birds of prey. One expedition through this same area in late May and early June we saw over 50 sloths. I only saw one sloth this entire trip. If we had come to study sloths we would have gone home with no data.

The ranger at the entrance warned us that the river was blocked with aquatic vegetation and we might not be able to navigate. Be careful, use our best judgment. For two hours there was no blockage at all. We could proceed with no problems. We cruised along at 6 kilometers per hour birdwatching, came slow around a bend and ha, ha, you guessed it, the river was blocked with bog as far as the eye can see. If I had never been stuck in a bog maybe I would not have worried. But bogged down had serious implications with me. I knew how hard it could be to get through. But the difference between success and failure hung in the balance so we plowed ahead. I won’t bore you with the details but we progressed slowly and it felt good to see open water in the distance and then we broke free and I relaxed. Of course we still had to get back out…but not for a few days.

As soon as we cleared the bog Pink Dolphins were on both sides of us. We decided to swim with the dolphins and then record. The water felt great at 10 degrees below air temperature. The water here is always stained with tannic acid but is nearly free of sediment. We could see lots of small fish, and the dolphin were feeding on them, but kept a distance of at least 75 yards between us.

After the swim Dave was ready to get to work. We made a couple of recordings. The second recording was distinguished by one dolphin that sounded angry. Maybe it always sounded angry but for the rest of our time in the reserve I never again heard a dolphin make a sound that I could interpreted as anger.

In the late afternoon we came to a location that caught our attention. Two incredibly beautiful large parrots took flight from a tree right next to a small band of howler monkeys. Usually that means a ripe food source and makes the best wildlife observation position. We tied up and decided to wait there till morning and soon the parrots came back. The next morning the Howler Monkeys were making their growling, dangerous sound close by. Saki and Squirrel Monkeys came to feed with the parrots. We could have tramped in the rainforest all day and not have seen as much wildlife as we saw sitting there in our comfortable chairs near that ripe fruit tree in two hours.

After checking in at the next ranger’s station we proceeded up the Yarina River to the Yarina Cocha, the largest lake in Pacaya Samiria National Reserve. We shut down and drifted with the breeze, alternating between recording, swimming, doing some laundry, and napping. During this time, one of the old legends came to life.

The legend of the Pink Dolphin is the opposite of the Mermaid Siren. The Pink Dolphin has supernatural powers to transform itself into a charming handsome man that seduces the innocent women living near the water. Any woman who comes up pregnant who should not be pregnant can blame the suave man that mysteriously emerged from the waters.

When the men left the water in Yarina Cocha the women stayed and played on the back of the boat, splashing and laughing. Within minutes their laughter intensified, intermingled with shrieks of delight. I watched from the observation deck as the dolphins put on a show. They repeatedly raised their heads out of the water and looked toward the amazed women on the swimming platform at the water line. Our boat drifted closer and the dolphins did not mind at all. The more the women laughed and shrieked and pointed and yelled the better the dolphins seemed to like it, and the more they increased their performance. I have truly never seen anything like it. It was a once in a life time experience for all of us.

The males are generally much larger (8 feet) than the females (6 feet), and usually pinker. We saw their heads swivel as if on necks. Their beaks have teeth. The fluke lies horizontal in the water as a whale’s, instead of vertical, as a fish’s.

We learned Pink Dolphins emit a sound 10 times above what the human ear can detect. They use that frequency for echolocation, similar to sonar. We recorded many variations of clicks and chirps that must be communication between dolphins. There is great variation in the noise made while sounding and it seems likely that is also communication, such as the dolphin that sounded angry. Of course we do not know that it was communicating anger. It would be a mistake to place human values on their sounds. I observed a huge, very pink dolphin, which in my mind could only have been a male, raise more than the lower third of its body and tail straight up, hold it vertically for few seconds, and then slam it down on the water as violently as possible. That was a form of communication also. This is a rich field of study worthy of a research grant.

We left Yarina Cocha the next morning thinking we had the ultimate dolphin sightings, but nothing could prepare us for what we witnessed in Atun Cocha. We tied up, and recorded dolphins for a while, then went for a swim. After the men left the water, the women, purely in the interest of science, ha, ha, tried to lure the same display as they had received the day before on Yarina Cocha. This was a tougher crowd in Atun Cocha and nothing particularly interesting took place for a long time. I think the women had given up when something amazing happened. Two of the largest and pinkest males started a commotion and got our attention. They were at least 50 to 75 yards away from the front of the boat when they both simultaneously jumped completely out of the water and chest butted each other. They thrashed and fought on the surface and then a female came to the surface and the “winner” took her. I will never make a great photo journalist. I stood there dumbstruck with the wrong lens, and was so hypnotized by the action I did not take one photo until it was all over.

What I did get a photo of, after it was over, is unexplainable. One of them held it’s beak out of the water for several minutes with a piece of wood grasped between its teeth. Now why would a Pink River Dolphin that just had sex, have a piece of wood in its beak?

Dave has a lot of data to analyze and it will take time, but he has promised to post some comments about his findings here on the Captains Blog.

To see photos of our eight day expedition to Pacaya Samiria National Reserve, including several photos of Pink Dolphins, click this live link: http://www.flickr.com/photos/dawnontheamazon/sets/72157594555573992/

Captain Bill reporting from the Crows Nest.

Observations about Our Study of Pink River Dolphins in Pacaya Samiria National Reserve

Bill Grimes, Pacaya Samiria National Reserve, Dawn on the Amazon Tours and Cruises

Links to other posts about Pacaya Samiria National Reserve, and Pink Dolphins;

An Interview with David Bonnett, Acoustical Engineer Studying Pink Dolphin Communication

I am just another travel man

Our Adventure Apprehending Paiche Poachers in Pacaya Samiria National Reserve

The Pacaya River

The story of our second scientific research expedition to record Pink Dolphin communication is at;

Pink Dolphins in Pacaya Samiria National Reserve 

Photos at Pink Dolphins, Pacaya Samiria National Reserve 

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