BEHAVIOUR OF THE AMAZON DOLPHIN 



59 



BlOTOP 



Ail observations were made in the rivers Ibaré and Mamoré and in some 

 neighbouring lagoons in the area around Puerto Almacén (Trinidad, Beni 

 district, fig. 1). The Ibaré, which is approximately fifty mètres wide, is a slow 

 running river whereas the Mamoré is much wider and flows comparatively faster 

 fig. 5-7). The water level in the rainy season rises considerably. The water in 

 summer is a muddy yellow. During my visit in February 1968, rainfalls were 

 relatively rare and the water level was low which was exceptional for this time of 

 the year. The température hovered around 35 C C and humidity was at its maximum. 

 The température of the water varied between 28° and 30°C. The banks of the river 

 were covered with rain forest and the edges of the river were thick with reeds and 

 other aquatic plants. Clumps of matted water hyacinths and branches were often 

 seen floating in the current. Small farms are situated on the steeper banks of the 

 river Ibaré. The farmers live in bamboo huts and plant bananas, guavas, papaya 

 trees, sugar cane, maize and water melons. Puerto Almacén lies on a hill, has two 

 anchorages and a saw mill which is during the day rather noisy. The boats are 

 mostly canoës made from a tree trunk ( kt Palo Maria ") driven by paddle or a 

 small outboard motor. Sometimes a larger motor boat can be seen transporting 

 cargo and passengers up and down the river. The bed of the river is muddy sand. 

 No mammals were seen on the river banks during the day. Caymans are seldom 

 seen in the Mamoré and if so, only at night by torch light. On the other hand, 

 there are many water fowl, mostly cormorants and hérons. Both rivers are rich in 

 fishes. Piranhas are commoner in the lagoons where there is no current. Many 

 species of turtles can be found sunning themselves on fallen tree trunks at the 

 river's edges. Crabs were seen in the shallow water at the river's edge, the same 

 species that we found in the stomachs of the Inia (see chapter on Food). It was 

 not possible to identify the species as I have no systematic expérience of thèse 

 groups of animais. 



BEHAVIOUR PROTOCOL 



2.2.1968 

 Rio Ibaré 



Took the shortest route from Trinidad to Rio Ibaré. From there with a motor 

 boat up the river. Sunny weather with the température on the river 32°C. Speed 

 approximately 4 knots. The water level was high. Rain forest typical for Bolivia 

 along the river banks. Isolated small farms. A lot of aquatic birds although no 

 mammals. About a dozen buffeos sighted on the way to Puerto Almacén. They 

 differ in size, the smaller approximately 1.5 meters long and grey. The larger 

 animais measure up to 3 meters and are pink. Différences in behaviour are not 



