Cetaceans are a diverse group of aquatic mammals that includes whales, dolphins, and porpoises. Cetaceans are well-known for their high intelligence and complex social structures. Most cetaceans give birth to live young that are precocial, meaning that they are able to swim and nurse shortly after birth. Some of the larger whale species, such as the blue whale and the humpback whale, give birth to calves that weigh several tons. These calves are able to swim and dive almost immediately after birth.