Dolphins in the context of "Aquatic mammal"

Hearing range describes the frequency range that can be heard by humans or other animals, though it can also refer to the range of levels. The human range is commonly given as 20 to 20,000 Hz, although there is considerable variation between individuals, especially at high frequencies, and a gradual loss of sensitivity to higher frequencies with age is considered normal. Sensitivity also varies with frequency, as shown by equal-loudness contours. Routine investigation for hearing loss usually involves an audiogram which shows threshold levels relative to a normal.

Several animal species can hear frequencies well beyond the human hearing range. Some dolphins and bats, for example, can hear frequencies over 100 kHz. Elephants can hear sounds at 16 Hz–12 kHz, while some whales can hear infrasonic sounds as low as 7 Hz.

Cetology (from Greek κῆτος, kētos, "whale"; and -λογία, -logia) or whalelore (also known as whaleology) is the branch of marine mammal science that studies the approximately eighty species of whales, dolphins, and porpoises in the scientific infraorder Cetacea. Cetologists, or those who practice cetology, seek to understand and explain cetacean evolution, distribution, morphology, behavior, community dynamics, and other topics.

Cocos Island (Spanish: Isla del Coco) is a volcanic island in the Pacific Ocean administered by Costa Rica, approximately 550 km (342 mi; 297 nmi) southwest of the Costa Rican mainland. It constitutes the 11th of the 15 districts of Puntarenas Canton of the Province of Puntarenas. With an area of approximately 23.85 km (9.21 sq mi), the island is roughly rectangular in shape. It is the southernmost point of geopolitical North America if non-continental islands are included, and the only landmass above water on the Cocos tectonic plate.

The entirety of Cocos Island has been designated a Costa Rican National Park since 1978, and has no permanent inhabitants other than Costa Rican park rangers. While previously being portrayed as the largest uninhabited island within the tropics, this has been labeled a false claim, as the island of Fernandina in the Galapagos archipelago is also uninhabited and far larger in area. Surrounded by deep waters with counter-currents, Cocos Island is admired by scuba divers for its populations of hammerhead sharks, rays, dolphins and other large marine species. The wet climate and oceanic qualities give Cocos an ecological character that is not shared with either the Galápagos Archipelago or any of the other islands (for example, Malpelo, Gorgona or Coiba) in the eastern Pacific Ocean. Because of the unique ecology of the island and its surrounding waters, Cocos Island National Park became a UNESCO World Heritage Site in 1997. The island can only be reached by sea, which usually takes 36 to 48 hours.

Boreoeutheria (/boʊˌriːoʊjuːˈθɛriə/) is a magnorder of placental mammals that groups together superorders Euarchontoglires and Laurasiatheria. The clade includes groups as diverse as giraffes, pigs, zebras, rhinoceroses, dogs, cats, rabbits, mice, bats, whales, dolphins, and primates (monkeys, apes, and humans).

With a few exceptions, male boreoeutherians have a scrotum, an ancestral feature of the clade. The sub-clade Scrotifera was named after this feature.