The Bolivian river dolphin is a freshwater dolphin that lives in the Madeira River. While, in the past, it was considered to be a separate species, today, most of the scientific community classifies it as a subspecies of the Amazon river dolphin.
Older publications as well as some modern ones used to classify Bolivian dolphins as a separate species of the Amazon river dolphin, or Inia geoffrensis. Today, most of the scientific community recognizes the Bolivian variant as a subspecies with the scientific name Inia geoffrensis boliviensis, along with I. g. geoffrensis and I. g. humboldtiana – the Amazon river dolphin and Orinoco river dolphin, respectively. The species belongs to the genus Inia and family Iniidae.
The Bolivian river dolphin is the larger fresh water river dolphin in the world, with adults reaching lengths of over 2,5 meters and weighing in
excess of 185 kg. The species presents sexual dimorphism, with females being 16 percent shorter and up to 55 percent lighter than males. The body is strong and flexible, with the cervical vertebrae not fused. This allows the dolphin to turn its head 90 degrees in both sides. The snout is long, as is the case with other river dolphins.
The flippers are long and flexible – they further provide the dolphins with great maneuverability, which allows them to swim through flooded forests in search for food. The eyes are small, yet the dolphins have accurate eyesight. However, they strongly rely on their eco sonar to hunt, which is performed by using various sounds and the melon structure in the front of the head.
Bolivian river dolphin habitat and feeding
Due to the rapids and waterfalls of the Madeira River, the populations have been isolated into a narrow area of this river, most likely being responsible for the appearance of the distinct Bolivian subspecies. These prefer water that is at least 1 meter deep, yet they also adventure into flooded forests during the rainy season. These dolphins have among the most diverse range of food, consuming dozens of species of fish, crustaceans, and even turtles.
Females give birth to calves during the flood season, or between May and June, after a gestation of about 11 months. Thanks to the smaller size of the females, these can stay behind with the calves in flooded forests after water retreats for far longer than males, enabling young dolphins to get the energy needed for development. Bolivian river dolphin calves usually stay with their mothers for 2 to 3 years.