Bottlenose Dolphins

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  1. Scientific Name: Tursiops truncatus
    Common Name: Bottlenose Dolphin
    Location: Temperate and tropical marine waters worldwide; In the Pacific, they are found from northern Japan to Australia and from southern California to Chile; In the Atlantic, they are found from Nova Scotia to Patagonia and from Norway to the tip of South Africa; In the Indian Ocean, they are found from Australia to South Africa
    Habitat:Primarily temperate and tropical waters; coastal ecotype typically inhabits nearshore waters including harbors, bays, lagoons, gulfs, estuaries, with occassional forays into large rivers; offshore ecotype typically inhabits pelagic regions extending to the continental shelf as well as select atolls and ocean islands

  2. Assocations: Bottlenose dolphins have been seen in groups of toothed whales such as pilot whales, spinner dolphins, spotted dolphins, and rough-toothed dolphins. Also, Bottlenose dolphins have been seen riding the pressure waves of gray whales, humpback whales, and right whales. Lastly,Dolphins respond to sharks with tolerance, avoidance, and aggression. Tiger sharks elicit the strongest responses from dolphins. Researchers have observed dolphins attacking, and sometimes killing, sharks in the wild
  3. How it Eats: Dolphins are active predators and eat a wide variety of fishes, squids, and crustaceans such as shrimps. The foods available to a dolphin vary with its geographic location.
    • Coastal dolphins tend to eat fishes and bottom-dwelling invertebrates.
    • Offshore dolphins tend to eat fishes and squid.
    • Some offshore dolphins were found with deep-sea fishes in their stomachs. This evidence suggests that offshore dolphins may dive to more than 500 m (1,600 ft.).
    • Bottlenose dolphins often cooperate when hunting and catching fish. In open waters, a dolphin group sometimes encircles a large school of fish and herds the fish into a small, dense mass. The dolphins take turns charging through the school to feed. Occasionally dolphins herd schools of fish against sand bars, shorelines, or mud banks to trap them in shallow water where the fish are easy prey. Dolphins also feed on individual, nonschooling fishes. Another way bottlenose dolphins eat is by  feeding in association with fishing operations. Dolphins may accompany shrimp trawls or other fishing vessels and feed on discarded fishes caught incidentally in the nets.
    How it Swims: Bottlenose dolphins swim by moving their tail flukes up and down through the water. They use their pectoral flippers to steer while swimming, to stroke, or to touch each other. Bottlenose dolphin “friends” or closely bonded dolphins may swim turning or twisting, or face to face touching flippers.
  4. Cohabitation: Bottlenose dolphins live in fluid social groups.In the past, bottlenose dolphin groups have been referred to as pods—social groups of unchanging composition. More recently, long-term studies of bottlenose dolphins have now shown that their group composition changes.Bottlenose dolphins commonly swim in groups of 2 to 15 individuals. Several groups may temporarily join (for several minutes or hours) in open ocean waters to form larger groups during which the dolphins may change associates. In general, group size tends to increase with water depth and openness of habitat. This may correlate with foraging strategies and protection. • Some group members establish strong social bonds.
  5. Communication: Bottlenose dolphins identify themselves with a signature whistle. However, scientists have found no evidence of a dolphin language. A mother dolphin may whistle to her calf almost continuously for several days after giving birth. This acoustic imprinting helps the calf learn to identify its mother. Another way dolphins communicate is by echolocation. The term echolocation refers to an ability that odontocetes (and some other marine mammals and most bats) possess that enables them essentially to "see" with their ears by listening for echoes. Odontocetes echolocate by producing clicking sounds and then receiving and interpreting the resulting echo
  6. Human Influences:  Dolphins, particularly coastal animals, are affected by heavy boat traffic, habitat destruction, and pollution. Industrial and agricultural pollutants in coastal habitats have resulted in high levels of toxins in the water and high concentrations of toxins in dolphin tissues.In the past, bottlenose dolphins have been taken directly for meat, leather, oil, and meal (for fertilizer and animal feed). Hunting still occurs in various parts of the world including Peru, Sri Lanka, Taiwan, and Japan.In the course of fishing operations, gear and nets can accidentally entangle and injure or drown dolphins.