Suborder ODONTOCETI (Toothed Whales)

The members of this branch of cetaceans are generally much smaller than the baleen whales, but they are far more numerous. They all have teeth, and the number of teeth is variable. They comprise about 70 species in six families. One of these families, the Monodontidae, has two species, the Narwhal Monodon monoceros and the Beluga Delphinapterus leucas, neither found in Indian seas. Another, the Platanistidae or river dolphins family, has one member, the Ganges-Indus River Dolphin Platanista gangetica in India, which lives in some rivers and not in seas. A few species, such as the endangered Chinese Beiji Lipotes vexillifer are now placed in a family called the Iniidae. No member of this family is found in India. The largest family of odontocetes, the Delphinidae, or oceanic dolphins, is well represented here, and in the northern Indian Ocean in general. One species of the family Phocoenidae, the true porpoises, is found in the coastal region. All the physeterids or sperm whales have been recorded from the area, and lastly, a few of the elusive Ziphiidae or beaked whales have been recorded.

Toothed whales range in size from 1.6 m dolphins to the 18 m long Sperm Whale Physeter macrocephalus. They occur in a wide variety of habitats from fresh water rivers to the deep parts of the ocean.

Many toothed whales live in large groups and have feeding routines. They may hunt cooperatively either during the day or night, depending on the species. Some species form associations with other odontocetes. The two species may then take turns during day and night to look out for sharks, a threat to these mammals in waters far from land.