Hector's and Maui's Dolphins: Endangered Animals of New Zealand
Two of the Rarest Dolphins in the World
The Hector’s dolphin and the Maui’s dolphin are found only off the coast of New Zealand and are two of the rarest dolphins on Earth. The population of Hector’s dolphins may consist of fewer than 7,500 individuals. The critically endangered population of Maui’s dolphins likely consists of around 50 to 60 animals. The pressure to protect and conserve these marine mammals is becoming intense, especially in the case of the Maui’s dolphin, whose population requires an emergency intervention.
The Maui’s dolphin is a close relative of the Hector’s dolphin. Both animals are relatively small members of the order Cetacea, which includes whales, dolphins, and porpoises. They are light grey animals with black and white markings and have a uniquely shaped dorsal fin along their backs. This fin is rounded instead of being sickle-shaped as in other dolphins. It's often said to look like one of Micky Mouse's ears.
New Zealand consists of two sections—the North Island and the South Island. Dolphins can be found by both islands.
Hector's and Maui's dolphins are classified in the same genus and species (the first two parts of a scientific name). However, scientists have decided that the genetics and skeleton of Maui’s dolphins are sufficiently different from those of Hector’s dolphins to warrant placing the animals in different subspecies.
The scientific name of Hector's dolphin is Cephalorhynchus hectori hectori while the Maui's dolphin is classified as Cephalorhynchus hectori maui. Hector's dolphins are found in three separated areas around the South Island of New Zealand. Maui's dolphins live on the west side of the North Island. They are sometimes referred to as the Maui dolphin.
Identification of the Hector's Dolphin
The endangered Hector's dolphin is named after Sir James Hector. Hector qualified as a surgeon but worked mainly as a geologist. He was the first director of the Geological Survey of New Zealand as well as the first director of the Colonial Museum. This museum is now known as the Museum of New Zealand, or Te Papa Tongarewa.
Hector's dolphins are one of the smallest marine dolphins in the world and reach a maximum length of about 1.5 meters (4.9 feet). They weigh between 40 and 60 kilograms (88 to 132 pounds). They are attractive animals. Their bodies are generally light grey in color but also have black and white areas. Their flippers, dorsal fin, and tail flukes are black and their face has a black mask. Their lower surface is white. A white stripe extends from the lower surface to each side of the body.
Unlike the familiar bottlenose dolphins that are sometimes kept in captivity, Hector's dolphins don't have a "beak". The beak is a projection formed by the extension of the jaws beyond the rounded upper head.
Hector's Dolphins Swimming in the Wild
Hector's dolphins live mostly in shallow water less than 100 meters deep and are found close to the shore. New research suggests that more of the animals live further away from the shore than was previously realized, however. The animals live in groups called pods, which consist of two to twelve animals. Pods sometimes join to form larger groups.
The dolphins feed mainly on fish and squid, which they catch in dives lasting about ninety seconds. Food is caught on the ocean floor, in the water, or at the surface of the water. Like all mammals, the dolphins breathe air and must periodically surface to obtain oxygen.
Like other cetaceans, both Hector's and Maui's dolphins find their prey by echolocation. During this process, a dolphin emits very high frequency sounds, also known as ultrasonic sounds. The sound waves bounce off solid objects and return to the dolphin, enabling it to judge the size, shape, distance, and direction of the objects. The animals also produce audible clicks and whistles as they communicate with each other.
Hector's and Maui's dolphins are active, curious, and confident animals. Maui's dolphins have been observed playing with seaweed, blowing bubbles, chasing each other, jumping out of the water, and fighting. Both dolphins like to swim close to boats. Some Hector's dolphins will swim next to humans in the water.
Hector's and Maui's dolphins are both slow breeders. The females don't reproduce until they are about 7 to 9 years of age. They have only one calf (the name for a dolphin baby) every 2 to 4 years. The gestation period is about ten to eleven months. The calf stays with its mother for as long as two years.
The latest research suggests that Hector's dolphins live for around twenty years, so a female may have a maximum of four calves in her lifetime. This slow rate of reproduction means that the death of a few animals will have a serious effect on the population. The New Zealand Department of Conservation says that twenty years is a short lifespan compared to that of other dolphins.
An Encounter With Maui's Dolphins
Until relatively recently, Hector's dolphins in New Zealand were classified into four groups, including the three groups around the South Island and the group beside the North Island. In 2002, research carried out by Dr. Alan Baker determined that the North Island dolphins were genetically distinct from the South Island ones. The North Island animals were placed in a different subspecies and given the name Maui's dolphins, while all the dolphins around the South Island continued to be known as Hector's dolphins.
The Maui's dolphin is the most endangered marine dolphin in the world. It looks very similar to the Hector's dolphin. It has a bigger skull and a slightly longer snout, however. It also has differences in its DNA, the molecule that contains its genes. If the animal becomes extinct, some of the genetic diversity of its species will disappear.
Countdown to Extinction
Estimates of Population Size
The population of Hector's dolphin is estimated to be around 7400 individuals. The Maui's dolphin population is estimated to be as low as 45 animals or as high as 63 animals over the age of one. Different sources give different values. The estimated numbers of the Maui's dolphin are so small that the loss of even one animal would be a serious event for the subspecies.
It's thought that close to 30,000 Hector's dolphins lived around New Zealand in the 1970s. This number is greatly reduced today. The IUCN (International Union for Conservation of Nature) classifies the Hector's dolphin population as endangered and the Maui's dolphin population as critically endangered. "Critically" endangered means that the animals are in serious danger of extinction.
Some people think that losing the Maui's dolphin would be sad but not tragic because the similar South Island dolphins still exist. Even if people support this idea, the situation is still serious because the entire species, including the South Island subspecies, is endangered.
The biggest threat to both dolphins is fishing by set (gill) nets and trawling nets. The dolphins seem to have difficulty detecting the nets. It's thought that they use echolocation only some of the time while they're swimming. Maui's dolphins live closer to shore than Hector's dolphins, making them more susceptible to danger from fishing nets. The dolphins become entangled in the mesh of the nets. This stops them from reaching the surface to breathe and causes them to drown.
Some dolphins are struck by boats. Youngsters are particularly susceptible to being damaged by boat propellers because they swim more slowly than adults and also tend to swim closer to the surface of the water. Pollution and coastal developments hurt the dolphins' population as well.
Another potential danger for Maui's dolphins is seabed mining in the area where they live. A marine mammal sanctuary has been established in the area, however. Seabed mining is prohibited close to shore within the sanctuary. Set nets and trawling nets are also prohibited close to shore. A map showing protection measures can be seen at the Department of Conservation website for the Maui's dolphin. The link is given in the "References" section below.
Maui's Dolphin Day in New Zealand
The restrictions that have been put in place to protect the Maui's dolphin sound like a good beginning. Some conservationists who are familiar with the area where the dolphin lives are unhappy, however. They say that the protection measures don't cover enough of the animal's habitat. The conservationists are pressing for new fishing regulations. The fishing industry says that the livelihood of their workers is threatened by the regulations.
The problem is that the debates and disagreements are taking up valuable time which is needed to prevent the extinction of the Maui's dolphins and allow the populations of both dolphin subspecies to increase. Losing either of these animals would be very sad.
© 2012 Linda Crampton