Dolphins exist throughout the world's water systems, and are considered to be among the world's most intelligent species. They vocalize to one another through clicks and whistles, and use echolocation as a method of "sight" underwater, enhancing their ability to perceive objects and prey.
Dolphins are under constant threat from a variety of human activities, such as the destruction of their habitats, accidental capture in fishing nets, and in some places, hunting. Many nonprofit organizations work to protect dolphins, both locally and internationally. National organizations such as World Wildlife Fund (3-star) and the Humane Society of the United States (3-star) have specific programs designed to both inform the public and protect dolphins from humans.