Facts About Hector's Dolphins
Hector's dolphins (Cephalorhynchus hectori) are the smallest members of the delphinae family of dolphins of which there are 32 species worldwide and one of the smallest cetaceans in the world. They are named after Sir James Hector, a New Zealand zoologist who collected the first specimen in 1869.
Physical Description
Although they are small they have a solid, robust body with a uniquely rounded, dorsal fin. The female of the species grows to 1.2 - 1.6 metres in length and can weigh up to 40 - 60 kg. Males do not grow quite so long and weigh around 10 kg less. The male reaches maturity between the ages of 6 - 9 years and the female from 6 – 9 years of age.
Their back and sides are a light grey, with white stripes, or flashes on the sides of their body. Their face, flippers, tail and dorsal fin are black. On their heads between the eyes and the blow hole is a crescent-shaped black mark.
Population and Range
Hector's dolphins are one of the rarest of the marine dolphins and only found around the coasts of New Zealand. It is believed that in the past they were more widespread and with greater abundance, with small populations off the North Island of New Zealand.
There are known to be four genetically different populations of Hector's dolphin all centred around New Zealand. The total population today is estimated to be around 7,400 animals. There is also a sub-species called Maui’s dolphin living off the west coast of North Island which is the rarest and smallest known sub-species of dolphin in the world.
Hector's dolphin likes inshore waters such as estuaries, river mouths and shallow coves and bays usually staying about 5 nautical miles from the shore. In winter they extend their range to about 15 nautical miles from shore.
Diet
Feeding is often a social activity and they feed on fish and marine animals such as red cod, mackerel, flounder, squid and crabs that live in shallow waters with a sandy bottom.
Echolocation
Like other cetaceans and animals such as bats they use echolocation to identify and catch their prey and to find their way around their underwater environment. In areas they are familiar with they can move around comfortably without using echolocation.
They use echolocation by making a stream of high pitched clicking noises which bounce off objects and return to the dolphin giving it a kind of map of their surroundings and what may be in it. They can even tell what an object is, whether if it is a fish, what type of fish, how fast and which direction it is moving in, and even how fast it is moving.
Social Structure
Hector's dolphins tend to form groups of up to five members and may temporarily join with another group. Their young are believed to play games with seaweed and also by blowing bubbles which are thought to develop social behaviours. Some of the clicking sounds they make are believed to be a form of communication especially when they are in a group.
Breeding
They usually give birth towards the end of spring or in early summer. The mother will not give birth again until the calf achieves full independence from her.
Conservation Status and Threats
In 1999 the New Zealand Department of Conservation rated Hector's dolphin as a "threatened species." Because of their coastal habitat they are vulnerable to threats of pollution from human settlements on the shores. Polluted rivers emptying into the sea and from oil and chemical spills from ships are also a risk. Chemicals such as DDT and PCB may also accumulate in their body adversely affecting reproduction.
The main danger they face is becoming entangled in nets, especially gillnets intended to catch other species. It is thought possible that their total population has been reduced from between half and a third from bycatch since 1970. Because they live in small scattered populations the risk of local extinctions from a pollution incident or from bycatch is greatly increased.
Modification and changes to their environment also put them in danger with more ports being expanded or constructed and the increasing development of aquaculture. There are also more recreational boats and dolphin watching tours are increasing in popularity bringing an increased risk of collisions with them and there are studies currently be done to explore this.
© 07/04/2014 zteve t evans
Although they are small they have a solid, robust body with a uniquely rounded, dorsal fin. The female of the species grows to 1.2 - 1.6 metres in length and can weigh up to 40 - 60 kg. Males do not grow quite so long and weigh around 10 kg less. The male reaches maturity between the ages of 6 - 9 years and the female from 6 – 9 years of age.
Their back and sides are a light grey, with white stripes, or flashes on the sides of their body. Their face, flippers, tail and dorsal fin are black. On their heads between the eyes and the blow hole is a crescent-shaped black mark.
Population and Range
Hector's dolphins are one of the rarest of the marine dolphins and only found around the coasts of New Zealand. It is believed that in the past they were more widespread and with greater abundance, with small populations off the North Island of New Zealand.
There are known to be four genetically different populations of Hector's dolphin all centred around New Zealand. The total population today is estimated to be around 7,400 animals. There is also a sub-species called Maui’s dolphin living off the west coast of North Island which is the rarest and smallest known sub-species of dolphin in the world.
Hector's dolphin likes inshore waters such as estuaries, river mouths and shallow coves and bays usually staying about 5 nautical miles from the shore. In winter they extend their range to about 15 nautical miles from shore.
Diet
Feeding is often a social activity and they feed on fish and marine animals such as red cod, mackerel, flounder, squid and crabs that live in shallow waters with a sandy bottom.
Echolocation
Like other cetaceans and animals such as bats they use echolocation to identify and catch their prey and to find their way around their underwater environment. In areas they are familiar with they can move around comfortably without using echolocation.
They use echolocation by making a stream of high pitched clicking noises which bounce off objects and return to the dolphin giving it a kind of map of their surroundings and what may be in it. They can even tell what an object is, whether if it is a fish, what type of fish, how fast and which direction it is moving in, and even how fast it is moving.
Social Structure
Hector's dolphins tend to form groups of up to five members and may temporarily join with another group. Their young are believed to play games with seaweed and also by blowing bubbles which are thought to develop social behaviours. Some of the clicking sounds they make are believed to be a form of communication especially when they are in a group.
Breeding
They usually give birth towards the end of spring or in early summer. The mother will not give birth again until the calf achieves full independence from her.
Conservation Status and Threats
In 1999 the New Zealand Department of Conservation rated Hector's dolphin as a "threatened species." Because of their coastal habitat they are vulnerable to threats of pollution from human settlements on the shores. Polluted rivers emptying into the sea and from oil and chemical spills from ships are also a risk. Chemicals such as DDT and PCB may also accumulate in their body adversely affecting reproduction.
The main danger they face is becoming entangled in nets, especially gillnets intended to catch other species. It is thought possible that their total population has been reduced from between half and a third from bycatch since 1970. Because they live in small scattered populations the risk of local extinctions from a pollution incident or from bycatch is greatly increased.
Modification and changes to their environment also put them in danger with more ports being expanded or constructed and the increasing development of aquaculture. There are also more recreational boats and dolphin watching tours are increasing in popularity bringing an increased risk of collisions with them and there are studies currently be done to explore this.
© 07/04/2014 zteve t evans
References and Attribution
Facts About Hector's Dolphins by zteve t evans - © 07/04/2014 zteve t evans
Image- File:Hectors Dolphin.jpg From Wikipedia - Cephalorhynchus hectori. Photograph by James Shook - Creative Commons Attribution 2.5 Generic license.
Hector's dolphin From Wikipedia
WWF Global - Hector's Dolphin
ARKive - Hector's dolphin (Cephalorhynchus hectori)
Facts About Hector's Dolphins by zteve t evans - © 07/04/2014 zteve t evans
Image- File:Hectors Dolphin.jpg From Wikipedia - Cephalorhynchus hectori. Photograph by James Shook - Creative Commons Attribution 2.5 Generic license.
Hector's dolphin From Wikipedia
WWF Global - Hector's Dolphin
ARKive - Hector's dolphin (Cephalorhynchus hectori)