The Boto Dolphin, also known as the Amazon River Dolphin, generally follows an S-growth curve graph. In the beginning, the population is low and increases at a low rate due to the struggle of finding food. The population of their prey, Amazon fish, began to sky-rocket, and as a result, the dolphin population also began to increase rapidly. Unfortunately, an increase in human subsistence fishing has depleted the population of fish in the Amazon, so the dolphin population suffered also.
During rain season, the amazon floods, and the dolphins migrate as a population, to the marshes and forest, in search of food, until the river levels lower back to normal. This is an example of immigration because the dolphins have to venture into a new place or they will starve.
Recently, the Amazon has seen a new trend of logging, the process of which has started to drive Amazon River Dolphins out of their natural habitat, forcing them to migrate to other areas of the river. Once the trees have been cut, it is a common practice to use the river as a way to transport the lumber from one end of the river to another. Unfortunately, this budget-friendly transportation artery disrupts the wildlife that reside in the river, and they must move.
As the population of the dolphin's food source, such as catfish, increases, so will the population of the dolphin, because there will be more available resources.
If the population of the catfish suddenly decreased, the availability of the dolphin's food source would be lowered, they would start to die off, allowing the catfish population to prosper and the dolphin population could increase.
Density-independent limiting factors
Natives in villages near the Amazon, are poaching thousands of the Amazon River Dolphins each year, for bait for catching catfish. This has resulting in a major decline and limits on the population.
Density-dependent limiting factors
The piranha population of the Amazon River, a major food source for River Dolphins, has decreased over recent years due to an increase in fresh-water crocodiles. This new competition is negatively affecting the Boto dolphins, who are struggling to strive off starvation long enough to reproduce.