There are seven species of whales currently on the endangered list. This represents over half of the great whale species that share the planet. The blue whale, the humpbacked whale, and the sperm whale are well known members of the endangered species list. The baiji whale is a species of toothed whale that lives in the Yangtze River in China. It is currently the most endangered species of whale, with only 300 of the whales remaining.
The reasons for the severe depletion of the whale population are numerous, but many causes can be tied directly to human behavior. At one point, whale products were in high demand across the world. This led to huge numbers of commercial whalers, who did not realize how rapidly they were decimating the numbers of whales in the ocean. As technology and communications improved, the plight of the whales became apparent and regulations were set in place to try to allow the whale populations to stabilize.
Other factors in whale endangerment include environmental changes. The oceans are difficult to study as an entire ecosystem. Whales in particular can be hard to study due to their large habitat ranges and the difficulty of tracking them for long term studies. This means that not as much is known about their breeding habits as we know about other mammals. It is very likely that human fishing and interference has reduced food supplies and has interfered with breeding grounds and patterns.