Four countries – Chile, Costa Rica, Hungary, and India – have declared dolphins to be "non-human persons" and have banned the capture and import of live dolphins for entertainment. They are one of the most studied and well-known marine mammals in the wild. Dolphins have also been known to kill porpoises for reasons which are not fully understood, as porpoises generally do not share the same diet as dolphins and are therefore not competitors for food supplies. Dolphins produce a variety of vocalizations, usually in the form of clicks and whistles. , In 1995, Marten and Psarakos used television to test dolphin self-awareness. The bigger, more moderate-sized dolphins include the popular bottlenose dolphin, which as an adult weighs 331 to 442 pounds (150 to 200 kilograms) and measures 6.6 to 12.8 feet (2 to 3.9 meters) in length, and the striking Pacific white-sided dolphin, which weighs 300 to 400 pounds (135 to 180 kilograms) and measures 5.5 to 8 feet (1.7 to 2.5 meters) in length when it reaches full maturity.  The Cornwall Wildlife Trust records about one such death a year. , The number of killer whales kept in captivity is very small, especially when compared to the number of bottlenose dolphins, with 60 captive killer whales being held in aquaria as of 2017[update]. Some species or specific populations have none, making them apex predators. Dolphins have rather small, unidentifiable spouts.  Though the terms 'dolphin' and 'porpoise' are sometimes used interchangeably, porpoises are not considered dolphins and have different physical features such as a shorter beak and spade-shaped teeth; they also differ in their behavior.  The name 'dolphin' is used casually as a synonym for bottlenose dolphin, the most common and familiar species of dolphin. Some species log out of the water, which may allow them to travel faster. The older a male dolphin is, the more likely his body is to be covered with bite scars.  This type of travel is known as porpoising. When dolphin meat is eaten in Japan, it is often cut into thin strips and eaten raw as sashimi, garnished with onion and either horseradish or grated garlic, much as with sashimi of whale or horse meat (basashi). , Archaeoceti is a parvorder comprising ancient whales. The epidermis of this species is characterized by the lack of keratin and by a prominent intertwine of epidermal rete pegs and long dermal papillae. There are several species of dolphin (almost 40). Roughly three categories of sounds can be identified: frequency modulated whistles, burst-pulsed sounds and clicks. Several species exhibit sexual dimorphism, in that the males are larger than females. , The primitive cetaceans, or archaeocetes, first took to the sea approximately 49 million years ago and became fully aquatic by 5–10 million years later. The military use of dolphins, however, drew scrutiny during the Vietnam War when rumors circulated that the United States Navy was training dolphins to kill Vietnamese divers.  A modern human-dolphin partnership currently operates in Laguna, Santa Catarina, Brazil. , Dolphins have torpedo-shaped bodies with generally non-flexible necks, limbs modified into flippers, a tail fin, and bulbous heads. This blubber can help with buoyancy, protection to some extent as predators would have a hard time getting through a thick layer of fat, and energy for leaner times; the primary usage for blubber is insulation from the harsh climate. , Dolphins also display culture, something long believed to be unique to humans (and possibly other primate species). Lastly, size does not always determine the types of food a dolphin is likely to eat.  In larger groups, individual whistle sounds are less prominent. This species’ dorsal fin is tall and curves backward. Eg 100 pounds… Divide by two = 50 Kg. At birth, newborn dolphins have hairs lined up in a single band on both sides of the rostrum, which is their jaw, and usually have a total length of 16-17 cm ..  While some reports state that the dolphins are becoming intoxicated on the tetrodotoxin in the fishes' skin, other reports have characterized this behavior as the normal curiosity and exploration of their environment in which dolphins engage. 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