Why Are There No Porpoises in the Croa River? The Croa River, in Cruzeiro do Sul (Acre), is one of the most beautiful natural settings in the Amazon, known for its flooded forest and rich biodiversity. However, unlike other Amazonian rivers, the Croa is not home to populations of dolphins, either the pink river dolphin (Inia geoffrensis) or the tucuxi (Sotalia fluviatilis). But why is this?
Characteristics of the river
The Croa River is a tributary of the Juruá River and has dark, calm waters surrounded by dense vegetation. Although it seems like a favorable environment for porpoises, some factors influence the absence of these animals:
Small volume of water: Compared to large rivers such as the Juruá and the Amazonas, the Croa has less depth and width, which can limit the presence of large aquatic mammals.
Food availability: Porpoises feed mainly on fish, and the amount available in the Croa may not be enough to sustain populations of these cetaceans.
Porpoises, especially the pink river dolphin (Inia geoffrensis), prefer larger, deeper rivers with wide channels, where they can swim freely and find plenty of food. The Croa River, being relatively narrow and shallow in some parts, may not offer ideal conditions for these animals.
Connectivity with other rivers
Why Are There No Porpoises in the Croa River? Porpoises usually move through large river systems in search of food and reproduction. The Croa River, being a smaller tributary, may not offer ideal migration conditions for these animals.
Porpoise preferences
Porpoises tend to inhabit larger rivers with deeper waters and a greater abundance of fish. The Juruá River, which is close to Croa, has these characteristics and is home to populations of porpoises. This suggests that the animals prefer to stay in areas that are more favorable for their survival.
Although the Croa River does not have dolphins, it is home to a great diversity of other species, such as ornamental fish, birds, caimans and turtles, making it an important Amazon ecosystem.
