4. Ganges River Dolphin
The Ganges River Dolphin is thought to be one of the oldest creatures in the world. It is a freshwater dolphin that is nearly blind, “seeing” with ultrasonic sounds. Although these dolphins are fresh water creatures, they are quite large, weighing up to 374 pounds and measuring up to nine feet in length. Interestingly, it is the females who grow to be this big. These unique creatures are threatened by being accidentally caught in fishing nets. They are also still hunted for their meat and oil. Pollution is a large problem faced by the Ganges River Dolphins. Up to 9,000 tons of pesticides are used near the river every year. These pesticides kill species that dolphins prey on and they pose a health threat to the dolphins, whose population is a mere 1,800.