Facts About Maui's Dolphin
Maui's dolphin (Cephalorhynchus hectori maui) is the rarest marine dolphin in the world. It is found off the west coast of New Zealand's North Island. Before the year 2002 it used to be called the North Island Hector's dolphin but Dr Alan Baker, after studying skeletal and genetic differences described it as a subspecies of Hector's dolphin (Cephalorhynchus hectori sp.) and was renamed Maui's dolphin after the Maori name for the North Island of New Zealand, which is Te Ika a Maui.
Physical Description
Maui's dolphins are one of the smallest cetaceans but have a robust, solid and strong body. They have a distinct half round shaped dorsal fin and a sloping snout. Adult Maui's grow to between 1.2 metres and 1.4 metres in length and weigh up to 50 kg.
They have a light grey back and their sides are also light grey with white flashes. They have a whitish underbelly and their tail, dorsal fin, flippers and face are black. Between their blowhole and their eyes there is a crescent shaped black mark.
Social Structure
Although they spend most of their time feeding they have at times been seen at play, which involves using seaweed, blowing bubbles, chasing and fighting other dolphins and jumping from the water. The young have also been seen in such activities which may act as an important social function.
Small nursery groups of mothers and calves are often formed for added protection when travelling. There are usually around five individuals in a group though sometime a group will join up with another temporarily.
Breeding
Maui's dolphins have a very low reproductive rate, tending to breed at just a fast enough rate to replace the population that dies naturally. This means they are having problems keeping their population stable when unnatural deaths occur.
Maui's dolphins do not pair for life. The females reach sexual maturity between 7 - 9 years of age give birth to a single calf every 2 - 4 years and have four calves in her 20 years of life.
The calf is born with its dorsal fin partly folded and with fold marks showing along its body. In proportion to its mother the calf is considerably large at 50 - 60 cm in length compared to its mother's length of 1.2 - 1.4 metres. Although calves learn to eat squid and fish after around 6 months of age they still feed on their mother's milk for the first 12 months of life.
Diet
They tend to spend most of their time making short dives to catch prey on the seafloor which last around 90 seconds. They also prey on squid and fish at mid water and at times closer to the surface.
Echolocation
Maui’s dolphins, like other cetaceans, use echolocation to hunt, find their way around their environment and possibly to communicate. They use a variety of clicks to create a kind of map of their local environment and what is in it. They do not use it all the time and it may that when it is not in use is when they become entangled in nets. Another reason for entanglement may be that the net material is too thin or does not bounce sound back.
Population and Range
In 1985 a survey estimated the total numbers of Maui's dolphins at 134. They were found to be living in isolated areas along the North Island’s North West coast. They tended to live in small social groups or pods of up to 5 individuals within 5 nautical miles from the shore.
During New Zealand's summer period they tend to be mostly be seen within 1 nautical mile of the shore. It is believed that individuals will spend their entire lives living along the same 60 km. In January 2004, a survey gave their population to be about 100 individuals. The New Zealand Department of Conservation estimated that there were perhaps as few as 55 individuals over the age of 12 months for the year 2010-11.
Clearly the plight of Maui’s dolphins is grave. Maui’s dolphin is listed on the IUCN Red List as “critically endangered” and the New Zealand Threat Classification System recognises it as Nationally Critical.” The New Zealand government is conducting more research and implicating a number of fishery and non-fishing measures that hopefully will help the survival of Maui’s dolphin.
© 11/04/2014 zteve t evans
Maui's dolphins are one of the smallest cetaceans but have a robust, solid and strong body. They have a distinct half round shaped dorsal fin and a sloping snout. Adult Maui's grow to between 1.2 metres and 1.4 metres in length and weigh up to 50 kg.
They have a light grey back and their sides are also light grey with white flashes. They have a whitish underbelly and their tail, dorsal fin, flippers and face are black. Between their blowhole and their eyes there is a crescent shaped black mark.
Social Structure
Although they spend most of their time feeding they have at times been seen at play, which involves using seaweed, blowing bubbles, chasing and fighting other dolphins and jumping from the water. The young have also been seen in such activities which may act as an important social function.
Small nursery groups of mothers and calves are often formed for added protection when travelling. There are usually around five individuals in a group though sometime a group will join up with another temporarily.
Breeding
Maui's dolphins have a very low reproductive rate, tending to breed at just a fast enough rate to replace the population that dies naturally. This means they are having problems keeping their population stable when unnatural deaths occur.
Maui's dolphins do not pair for life. The females reach sexual maturity between 7 - 9 years of age give birth to a single calf every 2 - 4 years and have four calves in her 20 years of life.
The calf is born with its dorsal fin partly folded and with fold marks showing along its body. In proportion to its mother the calf is considerably large at 50 - 60 cm in length compared to its mother's length of 1.2 - 1.4 metres. Although calves learn to eat squid and fish after around 6 months of age they still feed on their mother's milk for the first 12 months of life.
Diet
They tend to spend most of their time making short dives to catch prey on the seafloor which last around 90 seconds. They also prey on squid and fish at mid water and at times closer to the surface.
Echolocation
Maui’s dolphins, like other cetaceans, use echolocation to hunt, find their way around their environment and possibly to communicate. They use a variety of clicks to create a kind of map of their local environment and what is in it. They do not use it all the time and it may that when it is not in use is when they become entangled in nets. Another reason for entanglement may be that the net material is too thin or does not bounce sound back.
Population and Range
In 1985 a survey estimated the total numbers of Maui's dolphins at 134. They were found to be living in isolated areas along the North Island’s North West coast. They tended to live in small social groups or pods of up to 5 individuals within 5 nautical miles from the shore.
During New Zealand's summer period they tend to be mostly be seen within 1 nautical mile of the shore. It is believed that individuals will spend their entire lives living along the same 60 km. In January 2004, a survey gave their population to be about 100 individuals. The New Zealand Department of Conservation estimated that there were perhaps as few as 55 individuals over the age of 12 months for the year 2010-11.
Clearly the plight of Maui’s dolphins is grave. Maui’s dolphin is listed on the IUCN Red List as “critically endangered” and the New Zealand Threat Classification System recognises it as Nationally Critical.” The New Zealand government is conducting more research and implicating a number of fishery and non-fishing measures that hopefully will help the survival of Maui’s dolphin.
© 11/04/2014 zteve t evans
References and Attributions
Facts About Maui's Dolphin by zteve t evans - © 11/04/2014 zteve t evans
File:Two Maui's dolphins.jpg From Wikimedia Commons - Two Maui's dolphins - ©Department of Conservation, New Zealand - Creative Commons Attribution-Share Alike 3.0 New Zealand licence.
Estimating the abundance and effective population size of Maui’s dolphins using microsatellite genotypes in 2010–11,
with retrospective matching to 2001–07 Rebecca M. Hamner, Marc Oremus, Martin Stanley, Phillip Brown, Rochelle Constantine and C. Scott Baker
New Zealand Government Department of Conservation – Te Papa Atawbai/
WWF – Maui’s dolphin
Facts About Maui's Dolphin by zteve t evans - © 11/04/2014 zteve t evans
File:Two Maui's dolphins.jpg From Wikimedia Commons - Two Maui's dolphins - ©Department of Conservation, New Zealand - Creative Commons Attribution-Share Alike 3.0 New Zealand licence.
Estimating the abundance and effective population size of Maui’s dolphins using microsatellite genotypes in 2010–11,
with retrospective matching to 2001–07 Rebecca M. Hamner, Marc Oremus, Martin Stanley, Phillip Brown, Rochelle Constantine and C. Scott Baker
New Zealand Government Department of Conservation – Te Papa Atawbai/
WWF – Maui’s dolphin