Facts about bottlenose dolphin
Bottlenosed dolphins leaping out of the
water, Dusky Sound
Bottlenose dolphins (Tursiops truncatus) have a relatively short beak and a high, hooked and prominent dorsal fin. Colour is dark or light grey on the back grading to white on the undersides. Colour and shape can be variable however.
- Newborn: length 85 cm-1.3 m
- Adult: length 1.9-3.9 m
Range
Bottlenose dolphins are widely distributed throughout the world in cold temperate and tropical seas and generally do not range poleward of 45° in either hemisphere. New Zealand is therefore at the southern most point of their range. Limits to the range of this species appear to be temperature related. They are found both offshore and in many enclosed areas such as the Mediterranean, Black and Red Seas. Population densities appear to be higher close to shore, where these dolphins tend to travel in groups of about 30 individuals.
Population
Two global ecotypes have been recognised: those living in pelagic or open ocean environments and those living in coastal areas. Population sizes are largely unknown but this species is relatively common worldwide. In New Zealand three main coastal populations exist: around 450 individuals live in the Bay of Islands area, ranging from Doubtless Bay in Northland to Tauranga; around 63 live in Doubtful Sound, Fiordland (Bräger & Schneider, 1998); and another group range from the Marlborough Sounds to Westport. Bottlenose dolphins are commonly associated with other cetaceans including pilot whales, rough-toothed and Risso's dolphins, and humpback whales.
Diet and foraging
Individuals living close to the shore feed primarily on a variety of inshore bottom-dwelling fish and invertebrate species. Those offshore feed on mid-water fish species and oceanic squid. Their dives rarely last longer than 3-4 minutes inshore, but may be longer offshore. Individual feeding appears to be the most prevalent foraging method but individuals are also known to work together to herd schools of fish.
Life history
Females tend to reach sexual and physical maturity before males, leading to sexual dimorphism in some regions. Females usually reach sexual maturity at 5-13 years with males not maturing until 9-14 years of age. Females breed every 3-5 years and calves suckle for around 2-3 years. Calving peaks are known to occur for most populations between spring and summer/autumn. Female bottlenose dolphins can live up to more than 50 years of age, and males can reach as old as 40-45 years (Wells & Scott, 1999).
back to top