The baiji dolphin, also known as the Yangtze River dolphin, is one of the world's rarest mammals and is endangered due to competing for food with humans and China's economic growth. It is similar to the Chinese white dolphin but is now the most endangered cetacean. The baiji dolphin migrated to the Yangtze River 20 million years ago from the Pacific Ocean and is faster than sea horses but slower than tigers, bigger than cats but smaller than elephants, and more beautiful than pufferfish but uglier than red fish.