Acoustic Tracking Technology Using AI Helps Scientists Eavesdrop on Pink Dolphins, Track Their Movements in Amazon River

The water system of the Amazon River is home to two unique freshwater species of dolphins found only in South America's rivers. Unfortunately, they are endangered by the IUCN Red List of Threatened Species 2018.

Mapping the Movements of Endangered Dolphins

To aid the conservationist strategies of authorities, a group of researchers used artificial intelligence to track the movements of the dolphins across the rainforest, which gets submerged in the water every year after the rainy season. The study is also part of the teamwork between the Technical University of Catalonia and the Mamirauá Institute of Sustainable Development in Tefé, Brazil.

Conventional tracking techniques in similar studies include aerial drones, boats, or GPS tags. According to bioacoustician Michel André from the Technical University of Catalonia in Barcelona, Spain, the sound is much less invasive than traditional ones.

André and his colleagues studied the activity of two dolphin species, the boto - also known as the pink river dolphin - and the tucuxi, which are found in the floodplains of the Mamirauá reserve in the northern region of Brazil. They installed underwater microphones at various sites to eavesdrop on the situation of the animals.

To distinguish the sounds of the dolphin from the soundscape of the Amazon, the researchers used AI, where the recordings are fed into a deep-learning neural network. This neural network was trained to recognize the unique sounds of clicks and whistles produced by the dolphins. The technology allows the experts to analyze information that would otherwise be impossible to access.

The AI was trained to distinguish between three types of sound: dolphin, boat engines, and rainfall. The boto and tucuxi species use echolocation clicks to sense their environment, while they make whistling sounds when communicating with other dolphins. The neural network can effectively distinguish between the two species since each has distinct whistles.

Freshwater Dolphins of the Amazon

Botos (Inia geoffrensis) are a species of mammals considered the largest of the river dolphins. Also known as bufeo colorado, they are known for having pale pink color with a rounded head, long snout, and a small dorsal fin. They also possess a flexible neck which permits them to move their head from left to right.

Botos thrive throughout the Amazon and Orinoco River basins, feeding on over 43 fish species. They occur most often on the edges of rivers with lower densities concentrated at the center of large rivers. The botos population is not severely fragmented, although they are vulnerable to habitat degradation due to artificial activities.

Meanwhile, tucuxi (Sotalia fluviatilis) is another species of river dolphin that resembles a bottlenose dolphin but is smaller. Also known as bufeo negro, this animal is marked with dark stripes between its mouth and flipper.

Tucuxis are carnivorous, preying on marine ray-finned fishes supplemented with octopus and squid. The total population size of this animal is unknown today, although they face the threat of being caught in the gillnets of large fishing boats.

The boto population is estimated to decline by half every ten years, while the tucuxi population wanes at the same rate every nine years.