Eye on the Sea

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'The Rarest Marine Dolphin in the world'

Background
This species of Dolphin is named after Sir James Hector, an early explorer, geologist and naturalist.
The Hector's Dolphin is found only in (endemic to) New Zealand waters and is also the rarest of the world's oceanic Dolphin species. There are two varieties in New Zealand, a South Island and a North Island Hector's. While there is believed to be approximately 4000 Hector's Dolphins in the South Island population there are only about 100 North Island Hector's left, and this number is on the decline.

In 1999 The Department Of Conservation (DOC) recognized the Hector's dolphin as an 'endangered species' with the North Island Hectors classified as 'Critically endangered' by the International Union for Conservation of Nature (IUCN) in 2000. The main threat to the Hector's population is fishermen using gillnets; especially high levels of bycatch having been recorded in the Canterbury region.

Identification
The size and distinctive appearance of this unique Dolphin make it one of the easiest cetaceans to identify. They are by far the smallest dolphin species in New Zealand, with adults reaching only 1.2 - 1.4 metres in length. Unlike the usual 'bottle nose' shape, Hector's have a distinctive gently sloping snout that is more rounded and blunt; the round dorsal fin is also unusual and is unlike any other whale or dolphin.
The undersides of the Hector's are white with grey along the sides, and they have white flashes along the flanks of the body with distinctive black markings on the flippers, face, over each eye and up to the blowhole, dorsal fin and flukes. They are sexually dimorphic in the colouration of the genital area, with males having a grey oval mark around the genital slit; this is also further forward on the body of the male than of the female.

Habitat and Distribution
North Island Hector's are generally found on the North West coast of the North Island. One particular spot will be 'home' for small groups of 2-12 animals, sometimes for many years, sometimes for life. Hector's dolphins tend not to swim further than 30kms from their particular area, and these territory are generally close to the shore in a region between Taranaki and Dargaville.

South Island Hector's dolphins have a range roughly between Whanganui Inlet and Jackson Head on the West coast and between French pass and Oamaru on the East coast. They have also been sighted around Golden Bay and Tasman Bay on the North coast of the South Island. Occasionally they have been seen swimming short distances up rivers, particularly larger waterways such as the Buller and Grey river's.

Reproduction
The main factor governing the NI Hector's 'endangered species' status is its reproduction rate; Hector's are very slow breeders. The female only gives birth to four calves in her lifetime, a timespan of approximately of nineteen years.
The first calf is born when the female reaches maturity at 7-8 years, then again every 2-4 years after that; gestation is about 1 year.
Calves are very large (60-75 cm long) in comparison to the size of the adult female (120-140 cm) but are completely dependant on the parent for food and protection for the first year, and remain with the mother for anywhere from 3-6 years.
Mating occurs in late springtime, from September through to November.

Feeding
Hector's use echolocation to find their prey, and generally hunt in close to the coast in small groups, often diving over sandy bottoms. They hunt opportunistically taking a variety of fish species throughout the water column and off the substrate, including Kahawai and Mullet, squid, and benthic fish such as Stargazers and Red cod.
These dolphins have been observed chasing inshore trawlers targeting Flatfish and Red cod, taking the fish that the nets leave behind although rarely getting caught in these types of nets themselves. Strangely they seem to take no interest in dead fish thrown to them by the fishermen.

Communication
Unlike other dolphins Hector's make few sounds that are audible to humans and none of the squeaks and whistles heard from Bottlenose dolphins, -most of their sounds are clicks of too high a frequency for our ears to pick up.

These clicks are produced for the purpose of echolocation; for hunting fish, playing or communicating with other dolphins. By emitting a click and waiting for the sound to bounce back off an object the dolphin is able to determine how far away the object is, the time taken indicating distance, and the difference in frequencies giving the relative size of the object. Unfortunately gill nets are too fine to be detected by this echolocation technique, resulting in entanglement.

A large part of dolphin communication includes behaviours such as leaping, bubble blowing, spyhopping, lobtailing, surfing and playing with objects such as seaweed. These leaps and jumps of Hector's dolphins are social behaviours and lone dolphins aren't known to 'perform' in this way. In group situations, if one dolphin jumps it usually triggers others to follow suit.

Status and Conservation
At present, the odds are stacked heavily against the Hector's dolphin in its race for survival. Every single death is a huge blow to the population, increasing the chance of extinction within what is currently an estimated 50 years.
At present the mortality rate of Hector's dolphin is greater than their birth rate, with gill nets being the biggest threat to the species at present. The use of gillnets has also had a significant negative affect on coastal fish, with some species being seriously depleted. Some scientists believe that human over-fishing must also be having a detrimental affect on the Hector's dolphin by greatly reducing their available food resources.
A further complication is that younger dolphins are more susceptible to death by entanglement in gill nets than are older and 'wiser' individuals -the effect being to reduce the number of sexually mature and active breeding age dolphins available to replace ageing individuals.

What can we do?
Support the introduction of regulations restricting the use of gillnets in areas where Hector's dolphins are found, and encourage the use of more selective fishing methods.
Better yet, ban gillnetting outright as the unselective, archaic and destructive means of 'harvest' that it is.

And if we do nothing?
All New Zealander's will have to live with the shame of having allowed a unique and beautiful creature to be wiped forever from the face of the earth.