Common dolphins found in New Zealand waters belong to the species now known as the short-beaked common dolphin. The colouration of this dolphin is very distinctive with a criss-cross or hour-glass type pattern centred on the flanks. Colours include purplish black, grey, white and yellowish tan. The dorsal fin is high with a concave hind edge. The head is low and smooth-sloping.
The common dolphin (Delphinus delphis) is found in offshore warm-temperate waters in the Atlantic and Pacific and is the most numerous dolphin within this range. It is closely related to the long-beaked common dolphin (Delphinus capensis) which prefers shallower and warmer water.
Short-beaked common dolphins are found in waters throughout New Zealand and Australia. In New Zealand, this species tends to remain a few kilometres from the coast and is particularly common in the Hauraki Gulf and off Northland.
Common dolphin leaping out of the water, seen during a whale survey, Cook Strait Area
Common dolphins may form enormous schools of several thousand individuals. They are also known to associate with schools of pilot whales and other dolphin species such as dusky dolphins. This species is abundant but precise population estimates are largely unknown.
Diet and foraging
Common dolphins feed on a variety of prey, including surface schooling fish species and small mid-water fish and squids. They are known to dive to depths of 280 metres in search of prey and hunt cooperatively within schools. Dives can last up to 8 minutes but are usually between 10 seconds and 2 minutes. These animals are vocal and show a wide range of acrobatic behaviour.
Gestation lasts for around 10-11 months and the calving interval varies from 1 to 3 years. Age at sexual maturity is estimated to vary with region but for the Pacific is thought to range from 7-12 years for males and 6-7 years for females. Maximum age is estimated to be 22 years.
Common dolphin pod in the Cook Strait Area
Killer whales are the principal predators of common dolphins. When under threat individuals can be seen moving closer together. Dolphins have also been spotted with shark-bite scars indicating that sharks may predate on this species.
Large numbers of short-beaked common dolphins die in tuna purse seine fisheries in the eastern tropical Pacific and in set net fisheries around the world. In New Zealand common dolphins are caught in trawl fisheries each year. Tourism activities have also been found to affect the normal behaviour of these dolphins and studies have shown them attempting to avoid approaching vessels through the use of evasive behaviours (Au & Perryman, 1982). Boat strike is also a threat in areas of high boating activity such as in the Bay of Islands. Again, common sense rules should apply when boating around these dolphins to reduce stress on the animals. Such rules are outlined in the Marine Mammal Protection Regulations (1992).
View images of Dolphins killed in trawl nets.
Two common dolphins of the coast of Little Barrier Island
DOC is currently assessing the impacts of tourism on common dolphins in the Bay of Islands and is using photo-identification in the Bay of Plenty to study their population ecology. Future assessment will look at the effects of developing marine farm operations.
DOC is also responsible for managing stranding events.
You can help
When boating in the vicinity of dolphins, common sense rules apply and regulations exist so as disturbance and danger are minimised. General rules are outlined below:
- Operate your boat slowly and quietly at “no wake” speed
- Manoeuvre your boat sensitively near dolphins. Do not obstruct their path, cut through a group or separate mothers from calves
- Avoid sudden noises that could startle the animals
- Cooperate with others so all may see the dolphins without putting them at risk
- Only swim with dolphins with authorised tourist operators and avoid wearing suntan lotion as chemicals in the water can irritate the animals’ eyes
- Do not swim with dolphins when calves or juveniles are present
- Do not try to touch dolphins or feed them
Aircraft should also maintain a safe distance of at least 150 metres from dolphins and should not fly directly overhead.
Keep their environment clean by carefully disposing of any rubbish in appropriate receptacle, plastic waste can be particularly hazardous when discarded near waterways or beaches.
Common dolphin swimming, Cook Strait
Sightings of dolphins can be reported to the 0800 DOC HOTline (0800 362 468). These are always of interest and help increase our knowledge of cetacean distribution and movements around New Zealand. Useful information includes:
- number of individuals
- estimated sizes
- what they appeared to be doing
- the direction in which they were headed.
You can use the online form to report a dolphin sighting.
You can also download the marine mammal sighting form (PDF, 416K) or (Word, 4,300K - note this is a large file). These forms include images of marine mammals to help with species identification.
If you see set nets being used within closed areas then contact the Ministry for Primary Industries on 0800 4 POACHER (0800 4 76224).
If you catch or harm a dolphin
If you accidentally catch or harm a dolphin you have a legal obligation to report it as soon as possible, but within 48 hours, to DOC or MFish.
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