Bottlenose Dolphins

Tursiops truncatus & Tursiops aduncus

Biology of Bottlenose Dolphins

Dolphins

  • Dolphins are warm-blooded marine mammals and breathe air.
  • Dolphins can hold their breath for up to 15 minutes.
  • Dolphins are carnivorous and feed on a variety of sea life, including fish and squid.
  • A layer of fatty tissue under the skin, called blubber, maintains the dolphin's body heat. This layer of fat also provides an important energy source.
  • Dolphins have very good eyesight both above and below the water.
  • Following a gestation period of 12months, dolphins give birth to live young.
  • A bottlenose dolphin calf will drink milk for at least 6 months and remain with its mother for up to 4 years.
  • Age of maturity varies between genders, with female bottlenose dolphins reaching maturity between 8-10 years and males between 10-12 years of age.
  • Inshore bottlenose dolphins can grow between 1.9 to 3.9m and weigh between 150-650kg.
  • Dolphins can live for over 50 years.

Dolphin Societies

  • Dolphins are very social animals and live in complex societies that can often be sexually segregated and have a dominance hierarchy.
  • Groups of inshore bottlenose dolphins usually range between 1-10 individuals in size.
  • Mature males may form a strongly bonded alliance with at least four other males.
  • Females live in large groups and maintain a large network of associates within their home range.
  • Dolphins display many different types of behaviours including leaping, surfing, bow riding, and tail-slapping.
  • Bottlenose dolphins range throughout temperate and tropical waters throughout the worlds oceans.

Communication

  • Dolphins produce a diverse range of sounds that include echolocation or sonar clicks, whistles, burst pulse sounds such as 'squawks' and 'squeaks'.
  • 'Whistles' are thought to be used to maintain contact, identify, and to locate other dolphins.
  • 'Clicks' are used for echolocation, assisting in navigation and feeding.
  • Burst-pulse sounds not only assist in foraging and deciphering details about targets such as fish and other prey, but also have communicative functions. Little is known about the use of this diverse group of sound types produced by dolphins.

Byron Bay Dolphins

  • Byron Bay and its surrounding waters are an important habitat for over 500 'resident' and 'transient' dolphins.
  • Species of dolphins commonly seen in the Byron Bay region include Inshore Bottlenose Dolphins (Tursiops aduncus), Offshore Bottlenose Dolphins (Tursiops truncatus) and Common Dolphins (Delphinus delphis).

Threats to Dolphins

  • Marine mammals such as dolphins are protected in Australian waters, however, their future remains uncertain.
  • The largest threats to dolphins in Australia are pollution and habitat degradation. Many dolphin deaths in coastal waters have been attributed to ingestion of litter, boat strikes and pollutants such as insecticides.
  • Noise pollution from industrial or commercial as well as recreational noise sources such as vessels is also a significant threat endangering dolphins.
  • In other areas of the world, tuna fishing, gill netting and drift netting industries in addition to dolphin fisheries contribute to a large number of dolphin deaths each year.
  • The dolphin drive fisheries of Japan, Denmark and the Faroe Islands are still a large industry, killing thousands of dolphins each year.