These are organized by a classification scheme developed exclusively for Cosma. More…
dolphin : any of various small marine toothed whales (family Delphinidae) with the snout more or less elongated into a beak and the neck vertebrae partially fused
Note: While not closely related, dolphins and porpoises share a physical resemblance that often leads to misidentification. Dolphins typically have cone-shaped teeth, curved dorsal fins, and elongated beaks with large mouths, while porpoises have flat, spade-shaped teeth, triangular dorsal fins, and shortened beaks with smaller mouths. — Webster
Dolphins are a widely distributed and diverse group of aquatic mammals. They are an informal grouping within the order Cetacea, excluding whales and porpoises, so to zoologists the grouping is paraphyletic. The dolphins comprise the extant families Delphinidae (the oceanic dolphins), Platanistidae (the Indian river dolphins), Iniidae (the new world river dolphins), and Pontoporiidae (the brackish dolphins), and the extinct Lipotidae (baiji or Chinese river dolphin). There are 40 extant species of dolphins. Dolphins, alongside other cetaceans, belong to the clade Cetartiodactyla with even-toed ungulates. Their closest living relatives are the hippopotamuses, having diverged about 40 million years ago.
Dolphins range in size from the 1.7 m (5.6 ft) long and 50 kg (110 lb) Maui’s dolphin to the 9.5 m (31 ft) and 10 t (11 short tons) killer whale. Several species exhibit sexual dimorphism, in that the males are larger than females. They have streamlined bodies and two limbs that are modified into flippers. Though not quite as flexible as seals, some dolphins can travel at 55.5 km/h (34.5 mph). Dolphins use their conical shaped teeth to capture fast moving prey. They have well-developed hearing which is adapted for both air and water and is so well developed that some can survive even if they are blind. Some species are well adapted for diving to great depths. They have a layer of fat, or blubber, under the skin to keep warm in the cold water.
Although dolphins are widespread, most species prefer the warmer waters of the tropic zones, but some, like the right whale dolphin, prefer colder climates. Dolphins feed largely on fish and squid, but a few, like the killer whale, feed on large mammals, like seals. Male dolphins typically mate with multiple females every year, but females only mate every two to three years. Calves are typically born in the spring and summer months and females bear all the responsibility for raising them. Mothers of some species fast and nurse their young for a relatively long period of time. Dolphins produce a variety of vocalizations, usually in the form of clicks and whistles. — Wikipedia
Dolphins and Whales News -- ScienceDaily Whales and dolphins. Whale songs, beaching, endangered status -- current research news on all cetaceans.
Did mosasaurs hunt like killer whales?
on October 12, 2018 at 7:26 pm
Researchers have examined the youngest-ever specimen of tylosaur ever found. Like orcas, mosasaurs might have used their bony noses to strike prey. […]
Evolutionary 'arms race' -- how dolphins and...
on October 10, 2018 at 1:36 pm
A groundbreaking study reveals how dolphins, whales and other cetaceans compete for survival in an evolutionary 'arms race' with changing pathogenic threats like mercury and brevotoxin (e.g. Red Tide). Researchers show that cetaceans use several strategies for success in this race. They have developed tools to help wildlife managers and health professionals assess disease risk from the perspective of how individual animals are engineered to recognize the molecules of microorganisms in the […]
Polar bears gorged on whales to survive past warm...
on October 9, 2018 at 9:56 pm
A new study found that while dead whales are valuable sources of fat and protein for some polar bears, this resource will likely not be enough to sustain most bear populations in the future when the Arctic becomes ice-free in summers. […]
PCB pollution threatens to wipe out killer whales
on September 27, 2018 at 6:53 pm
A new study shows that more than 40 years after the first initiatives were taken to ban the use of PCBs, the chemical pollutants remain a deadly threat to animals at the top of the food chain […]
Aerial survey reveals great diversity and...
on September 14, 2018 at 2:03 pm
Airborne marine biologists were amazed by the sheer abundance and diversity of large marine wildlife in their recent aerial survey of the Northeast Canyons and Seamounts Marine National Monument, the only marine national monument on the East Coast, about 150 southeast of Cape Cod. […]