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Araguaia River Dolphin (Inia araguaiensis)

Mohamed bin Zayed Species project number 152510330

Population Assessment and Monitoring of the Araguaia River Dolphin (Inia araguaiensis)

Mohamed bin Zayed Species Conservation (Project No. 152510330) - Araguaia River Dolphin - Awarded $7,000 on November 01, 2015

Instituto Araguaia is a Brazilian non-profit NGO founded in 2010. Our mission to protect the biodiversity of the Araguaia River basin and its ecological processes, in particular in and around Cantão State Park. Cantão is an inland delta on the Araguaia RIver basin of Central Brazil, where the Cerrado and Amazon biomes meet. It is an area of exceptional biodiversity, especially of aquatic species. The park consists of 90,000 hectares of flooded forests and marshes, and contains 850 oxbow lakes and hundreds of kilometers of channels. This rich habitat supports large populations of aquatic predators like giant otters, black caimans, arapaima fish, and river dolphins. Through an agreement with Naturatins, the agency in charge of Cantão Park, we maintain a research base with four full time rangers in the interior of the park. Our permanent patrols create a sanctuary within the protected area where threatened species can live and be studied without human disturbance. We monitor and study the population of giant otters, arapaima and other predatory fish, river turtles, and migratory birds. We also work with the local community through educational programs for schoolchildren, by training local people to be ecotourist guides, by involving local fishermen in our fish research, and by maintaining the park's network of visitor trails. In 2014 we began work with the newly-described Araguaia River Dolphin. By using a small drone we were able to observe its underwater behavior for the first time, and discovered unique adaptations to deal with the shallows of the Araguaia wetlands.
In June 2015 we began to test a 4-meter helium blimp, to which we adapted a GoPro camera and gimbal stabilizer. By towing it behind an electric canoe, we found that we could easily observe and count the Araguaia river dolphin, even when they were underwater. Ms Julia Furstenau, Oliveira, a German-Brazilian student at the University of Freiburg, began a five-month stay at the base to validate this methodology. We also began the season's fish tagging, and intensified the search for giant otters. All this research activity meant lots of teams and equipment circulating around the area, which kept trespassing to a minimum.
In September an expedition was carried out to an area up the Rio do Coco where we detected a population of river dolphins isolated for the dry season. A team of four spent five days counting dolphins with the blimp, and also recording giant otters and arapaima sighted.
In October and November, we concluded the dolphin and fish research for the year. Over the course of two more expeditions, we completed a full count of all the Araguaia river dolphins that spend the dry season in our sector of the Park - perhaps 25% of Park's population, judging from the amount of available dry season habitat. All counts were performed multiple times simultaneously by the blimp and by three observers in a boat, and we were able to demonstrate that river dolphin counts by boat are unreliable, while the blimp's aerial footage makes accurate counts easy.
We estimated the population of the area we surveyed to be about 89 dolphins, distributed among five isolated bodies of water (the only places in our sector where river dolphins spend the dry season). Interestingly, 36 of the dolphins were concentrated in a single body of water, a stretch of the Rio do Coco isolated by sandbanks. This stretch runs along the Park's border, outside the protected area, once again demonstrating the importance of protecting both the Park and its surroundings. A total of 390 sightings were obtained, 7,9% of which were of young dolphins, 47% were of single individuals, 31,2% were of pairs and 13,4% were groups of three dolphins. The dolphin density in the park was estimated in 19,7 animals per square kilometer, which is much higher than densities reported anywhere else.
In terms of behavior Inia araguaiaensis is truly amazing: in the wet season, they chase fish among submerged tree trunks, deep in the flooded forest; in the dry season, they can belly crawl from pool to pool over sandbanks as shallow as 20 cm in search of prey. No other dolphin does this.
But this unique behavior also puts the dolphins at risk: tributaries of the Araguaia to the south of Cantão are being dammed and pumped nearly dry for large-scale agriculture. River dolphins become trapped in dwindling pools, where they can overheat and run out of fish prey before the floods return. This year, a dozen dolphins had to be rescued, and at least three died before they could be saved. With so few remaining in the wild, every individual counts. But capture and translocation in the tropical heat are also risky and traumatic for this delicate species. Instituto Araguaia must monitor groups of at-risk dolphins throughout the dry season, so that we can identify and rescue only those in imminent danger.
The rains have returned now, and the waters are rising, but we are making ready for the next dry season, when new irrigation projects will mean even more danger for the dolphins. We have identified a number of locations where dolphins may be at risk. Instituto Araguaia hopes to continue to monitor the dolphin population next dry season, and to organize timely rescues if necessary.

Project documents