Cetacea of any animal on earth, averaging and in mature males. The brain to body mass ratio in some odontocetes, such as belugas and narwhals, is second only to humans. In some whales, however, it is less than half that of humans: 0.9% versus 2.1%. The sperm whale ("Physeter macrocephalus") is the largest of all toothed predatory animals and possesses the largest brain. The cetacean skeleton is largely made up of cortical bone, which stabilizes the animal in the water. For this reason, the usual terrestrial compact bones, which are finely woven cancellous bone, are replaced with lighter and more elastic
Whale shark , with a weight of around . In 2011, more than 400 whale sharks gathered off the Yucatan Coast. It was one of the largest gatherings of whale sharks recorded. Aggregations in that area are among the most reliable seasonal gatherings known for whale sharks, with large numbers occurring in most years between May and September. Associated ecotourism has grown rapidly to unsustainable levels. Neither mating nor pupping of whale sharks has been observed. The capture of a female in July 1996 that was pregnant with 300 pups indicated whale sharks are ovoviviparous. The eggs remain in the body and