Māui dolphin: Difference between revisions
the species itself (Cephalorhynchus hectori) isn't rare, just THIS subspecies. |
m →External links: added link to NZ information page for Mauis Dolphins |
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* [http://www.forestandbird.org.nz/Marine/hectors/northisland.asp Forest and Bird] - Maui's dolphin page |
* [http://www.forestandbird.org.nz/Marine/hectors/northisland.asp Forest and Bird] - Maui's dolphin page |
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* [http://www.wdcs.org/ Whale and Dolphin Conservation Society] |
* [http://www.wdcs.org/ Whale and Dolphin Conservation Society] |
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* [http://www.mauisdolphin.com/ Mauis Dolphin New Zealand Event Information] Maui's Dolphin New Zealand Event Information |
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* [http://www.panda.org/what_we_do/endangered_species/endangered_species_list/cetaceans/about/hectors_dolphin/mauis_dolphin/ World Wide Fund for Nature (WWF)] - species profile for Maui's dolphin |
* [http://www.panda.org/what_we_do/endangered_species/endangered_species_list/cetaceans/about/hectors_dolphin/mauis_dolphin/ World Wide Fund for Nature (WWF)] - species profile for Maui's dolphin |
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Revision as of 11:54, 17 March 2012
| Māui dolphin | |
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| The parent species - Hector's dolphin | |
| Scientific classification | |
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| Phylum: | |
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| Species: | |
| Subspecies: | maui
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| Trinomial name | |
| Cephalorhynchus hectori maui | |
Maui's dolphin or popoto (Cephalorhynchus hectori maui) is the world's rarest and smallest known subspecies of dolphin.[1] They are a sub-species of the Hector's dolphin.
They are only found off the northwest coast of New Zealand's North Island, and are among that country's rarest subspecies. As of 2012, it is estimated that 55 Maui's dolphins exist in the world.[2]
Maui's dolphins are generally found close to shore in groups or pods of several dolphin. They are often seen in water less than 20 metres deep, but may also range further off shore. Most of their time is spent feeding.
Genetics
In 2002 it was discovered that Maui's dolphins were a sub-species of Hector's dolphin, previously they had been known as the North Island Hector's Dolphin. Dr Alan Baker found that genetic and skeletal differences in the Maui's made them distinct from the Hector's.[3]
Physical description
Having distinctive grey, white and black markings and a short snout, they are most easily recognized by their round dorsal fin. Maui's dolphins are generally found close to shore in groups or pods of several dolphins. They have a solidly built body with a gently sloping snout and a unique rounded dorsal fin. (Maui’s and Hector's are the only dolphins with a well-rounded black dorsal fin.)
Females grow to 1.7 metres long and weigh up to 50 kg. Males are slightly smaller and lighter. The dolphins are known to live up to 20 years.
Population and distribution
Maui's dolphins are only found off the west coast of the central and upper North Island of New Zealand, approximately between Dargaville and New Plymouth.[4] Most sightings of the dolphins are made in the centre of their range between Manukau harbour and Port Waikato, a 22 nautical mile distance.[5]
Its estimated that 55 individuals of the species currently remain in the wild. This is a marked decrease from a 2004 survey that found the population to be around 100 dolphins. An initial survey of Maui's dolphins in 1985 previously estimated their numbers to be at 134.[3]
They are classed by the Department of Conservation in the New Zealand Threat Classification System as "Nationally Critical".[6]
Ecology and behaviour
Vocalizations and echolocation
Maui's dolphins use echolocation to navigate, communicate and find their food. High frequency ultrasonic clicks reflect back to the dolphin any objects found in the water.[7]
Foraging and predation
Maui's dolphins feed on small fish, squid and ocean floor dwelling species like flatfish and cod.[8] Maui's dolphins spend much of their time making dives to find fish on the sea floor. They also find fish and squid in mid water and at times feed near the surface.[7]
Social behaviour and reproduction
Female Maui's dolphins aren't sexually mature until they are 7 - 9 years of age. They then produce one calf every 2 - 4 years.[9]
They have been observed playing (e.g. with seaweed), chasing other dolphins, blowing bubbles, and play fighting.
Threats
Gill net fishing has had an adverse effect on the Maui’s dolphin population. Some commercial set net fishers have acknowledged that they have occasionally caught Maui’s dolphin by accident in the past.
Since 2001, nine dead Maui's dolphins have been found dead and five of these deaths were confirmed to be caused by fishing.[10] In January 2012 a female Maui's dolphin was reported to be killed in a set net in Taranaki.[11]
References
- ^ "Dolphin's death reignites calls for set net ban". nzherald.co.nz. Retrieved 27/02/2012.
{{cite web}}: Check date values in:|accessdate=(help) - ^ New Zealand Department of Conservation. "Maui's dolphin abundance estimate: DOC's work". Retrieved 2012-03-13.
- ^ a b "Maui's dolphin". WWF. Retrieved 9/3/2012.
{{cite web}}: Check date values in:|accessdate=(help) - ^ "Maui's Dolphins". Forest & Bird. Retrieved 9/3/2012.
{{cite web}}: Check date values in:|accessdate=(help) - ^ "Rare encounter with Mauis dolphins". stuff.co.nz. Retrieved 14/3/2012.
{{cite web}}: Check date values in:|accessdate=(help) - ^ Hitchmough, Rod; Bull, Leigh; Cromarty, Pam (compilers) (2007). New Zealand Threat Classification System lists - 2005 (PDF). Wellington: Science & Technical Publishing, Department of Conservation. p. 32. ISBN 0-478-14128-9..
- ^ a b "Maui's dolphin - Ecology". WWF. Retrieved 10/3/2012.
{{cite web}}: Check date values in:|accessdate=(help) Cite error: The named reference "wwf ecology" was defined multiple times with different content (see the help page). - ^ "Dolphins and Porpoises (Families Delphinidae and Phocoenidae)". Treasures of the sea. Retrieved 15/3/2012.
{{cite web}}: Check date values in:|accessdate=(help) - ^ "Facts about Maui's dolphin". Department of Conservation. Retrieved 9/3/2012.
{{cite web}}: Check date values in:|accessdate=(help) - ^ "Maui's dolphin threats". WWF. Retrieved 11/3/2012.
{{cite web}}: Check date values in:|accessdate=(help) - ^ "Rare Maui's dolphin numbers still dropping". stuff.co.nz. Retrieved 27/02/2012.
{{cite web}}: Check date values in:|accessdate=(help)
External links
- Department of Conservation - Maui's dolphin page
- Forest and Bird - Maui's dolphin page
- Whale and Dolphin Conservation Society
- Mauis Dolphin New Zealand Event Information Maui's Dolphin New Zealand Event Information
- World Wide Fund for Nature (WWF) - species profile for Maui's dolphin