Hector's and Maui's Dolphins: Vulnerable and Endangered Animals
Unique Dolphins in New Zealand
The Hector’s dolphin and the Maui’s dolphin are found only off the coast of New Zealand. The latest population assessment of Hector’s dolphins estimates that around 15,000 individuals exist. They are classified as "nationally vulnerable". The critically endangered population of Maui’s dolphins likely consists of around 63 animals older than a year. 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 animals are close relatives. They are relatively small members of the order Cetacea, which includes whales, dolphins, and porpoises. They look quite similar and are light grey animals with black and white markings. The dolphins have a uniquely-shaped dorsal fin along their backs. The 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). 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 the Hector's dolphin is Cephalorhynchus hectori hectori while the Maui's dolphin is classified as Cephalorhynchus hectori maui. The first subspecies is found in three separate areas around the South Island of New Zealand. The second lives on the west side of the North Island. The dolphins that are seen in this location are sometimes referred to as Maui or Māui dolphins or as North Island ones.
Identification of the Hector's Dolphin
The 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 lack a "beak". The beak is a projection formed by the extension of the jaws beyond the rounded upper head.
The video below was made in 2016 and refers to a previous estimate of the Hector's dolphin population size.
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 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 (a government organization) says that twenty years is a short lifespan compared to that of other dolphins.
Facts About 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 isn't the most endangered cetacean, however. Only ten to fifteen vaquitas exist. This species is on the edge of extinction. The vaquita is classified as a porpoise, not a dolphin.
The Maui's dolphin 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. The video below shows the animal as it swims.
Estimates of Population Size
The population of Hector's dolphins is currently estimated to be around 15,000 individuals. The Maui's dolphin population is estimated to be approximately 63 animals over the age of one. The number of calves is unknown. Different sources give different values for the numbers. 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) says that around 7,381 mature animals exist and classifies the Hector's dolphin population as endangered. This status is based on a 2008 population assessment, however. Thankfully, according the the Department of Conservation and its more recent data, the population is approximately double that of the IUCN's claim and the situation doesn't seem to be quite so serious today.
Though the dolphin's status is better than it was and its population has appeared to stabilize, the animals still need some help, as the zoologists in the video below mention. (The video was posted on the last day of 2018.) Some otherwise useful sources of information, including the maker of the video, still refer to the IUCN's earlier assessment of the animal's status as "endangered". The IUCN is a respected organization. I wish it would update the dolphin's status and if necessary say why it disagrees with other assessments.
There is no disagreement about the plight of the Maui's dolphin. The animal's population is classified as critically endangered by all of the sources that I've seen. "Critically" endangered means that the animals are in serious danger of extinction. I find the situation a little concerning beyond the critically endangered status, though. The estimated population size of the animal has stayed the same for many years, which makes me wonder how accurate it is.
Threats: fishing, disease, oil and gas exploration, boat strike, mining, tourism, noise— New Zealand Department of Conservation (with respect to the Hector's dolphin)
The biggest threat to both dolphins is fishing by set (gill) nets and trawling nets. The dolphins seem to have difficulty detecting gill nets, which generally have a fine mesh. The mammals may be able to detect nets with a coarser mesh but find the source of trapped fish worth any risk in approaching them. Another contribution to the problem might be 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.
Some people might 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 South Island subspecies has a vulnerable status.
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 debates and disagreements are taking up valuable time that is needed to prevent the extinction of the Maui's dolphins and allow its population to increase.
One zoologist is happy that a protection zone has been established for the Hector's dolphin, allowing its population to stabilize. They also says that if the protection zone was extended, the population would likely increase and be safer. I think that protecting both of the subspecies of Cephalorhynchus hectori is important.
- Information about Cephalorhynchus hectori (Hector's and Maui's dolphins) from the WWF or World Wildlife Fund
- Facts about Hector's dolphins from the Department of Conservation, Government of New Zealand
- The Hector's dolphin entry on the Red List of the IUCN
- Maui dolphin facts from the Department of Conservation
- Information about Maui's dolphins from the IUCN
© 2012 Linda Crampton