cetaceans

Cetaceans are a diverse clade of fully aquatic mammals that includes whales, dolphins, and porpoises. They have streamlined bodies, forelimbs modified as flippers, and tail flukes for propulsion, while hind limbs are vestigial. Most species breathe air through lungs and surface to exhale and inhale through their blowholes.

Cetaceans are divided into two extant suborders: Mysticeti (baleen whales) and Odontoceti (toothed whales). Baleen whales filter prey with keratinous baleen plates, while toothed whales hunt individual prey and often use echolocation. Cetaceans belong to the larger clade Cetartiodactyla, with hippos as their closest living relatives.

Odontocetes use echolocation to locate prey and navigate in dark or murky waters, and they communicate with complex vocalizations. Mysticetes rely on low-frequency calls for long-distance communication. Most species have long gestation periods and give birth to a single calf after about 10 to 17 months, with calves nursing for months.

Cetaceans occur in most of the world’s oceans, with some species inhabiting freshwater rivers. They show diverse feeding strategies, from filter-feeding on small crustaceans to hunting fish, squid, and larger prey. Social structure varies from solitary individuals to large, coastal pods.

Conservation concerns focus on entanglement in fishing gear, ship strikes, pollution, noise from ships and industrial activity, and climate change. Several species are listed as threatened or endangered by the IUCN, with vaquita and certain right and baleen whales in the most urgent categories. Recovery depends on protective measures, habitat protection, and further research.