Dolphins

24.9.2012
Hannah

Different species Of There is some debate over how many different species of dolphins there really are. Some say there are 32 different species, while some say that there actually 33. It all depends on whether you think the White Whale counts as a dolphin or not. Some say that it does, some say that it doesn't.

Dolphin or Whale ?

The largest of all dolphin species is the Orca, which is commonly known as the Killer Whale. These dolphins can be over 31 feet long when fully grown, which has provided them with the unproper name of "whale".

Also, there are several different dolphins considered as the smallest dolphin species. These include True dolphins, Tucuxi dolphins, Hector's dolphins, Black dolphins, River dolphins, porpoises, and Commerson's dolphins.

Dolphins

• Common Dolphin
• Risso's Dolphins
• Bottlenose Dolphin
• White-Sided Dolphin
• White Beaked Dolphin
• Dusky Dolphin
• Falkland Island Dolphin
• Hour Glass Dolphin
• Peale's Dolphin
• Sarawak Dolphin
• Heaviside's Dolphin
• White Bellied Dolphins
• Irrawaddy River Dolphins
• Irrawaddy River Dolphins

Dolphin Facts

1.  Dolphins are mammals; they nurse their young from mammary glands.

2. Dolphins can swim up to 260 m. below the surface of the ocean, although they are mainly shallow divers.

·          Dolphins can stay up to 15 minutes under water, but they cannot breath under the water.

·          Dolphins use a technique called echolocation to find food and navigate.

·          Dolphins live in groups formed by 10 to 12 individuals.

·          There are 36 different kinds of ocean dolphins and 5 species of river dolphins.

·          The largest dolphin is the “killer whale” (also known as Orca).

·          The most known dolphin is the “ bottlenose dolphin”.

·          Dolphins are warm-blooded.

·          Dolphins communicate through sounds and whistles.

·          Dolphins eat fish and squid.

·          Dolphins are mammals NOT fish.

Hectors Dolphin

The brain of a 38-kilogram Hector’s dolphin weighs 640 grams. This is 1.7% of its total body weight – one of the highest proportions in the animal kingdom. It is bettered only by the typical proportion for humans of 1.9 %. But to what extent a big brain means high intelligence is not well established

Hector's dolphins do not live as long as others: the smaller the species, the shorter the lifespan.

Fishing is the most significant known threat to Māui’s and Hector’s dolphins.  Department of Conservation created marine sanctuaries throughout NZ where nets cannot be used in certain areas and at certain times of the year to protect Hector's dolphins.

Finding food and navigating under water by vision alone is tricky in murky water. Dolphins can use echolocation as well. They send out a stream of clicks and ‘read’ the echo that bounces back from hard surfaces, such as a rock wall or the taut swim bladder of a fish. This gives them information about size, density and distance.

Māori and dolphins

Many cultures have revered dolphins. The Greeks put people to death for killing them, and Māori often described them as taniwha, or water spirits.

The Ngāti Wai people, who used to live on the Poor Knights, Great Barrier and Little Barrier, believed that dolphins acted as messengers in times of need, bearing news from the islands to the mainland. The tribes living around Cook Strait talked of Paneiraira, a taniwha that resembled a whale. It would help canoes cross the tricky strait between the North and South islands.

The taniwha Tuhirangi guided Kupe, the mythical Polynesian explorer, to New Zealand. Later, Kupe placed Tuhirangi at French Pass in the Marlborough Sounds, to guide canoes through the treacherous waters. Tuhirangi lives there in a cave called Kaikaiawaro.

Friendly dolphins

In modern times, friendly dolphins – Pelorus Jack and Opo are the best known – have regularly made appearances around New Zealand’s coast.

Pelorus Jack, the speedy Risso

In 1888 a 4-metre Risso’s dolphin escorted a steamer from the outer Marlborough Sounds towards Nelson. He became known as Pelorus Jack, and Māori naturally recognised him as the taniwha Tuhirangi. From then on until his disappearance in 1912, he accompanied ships for a distance of about eight kilometres to and from French Pass, the dangerous passage separating D’Urville Island from the mainland. If the dolphin had to choose between two boats he would pick the faster, and could easily outpace a vessel travelling at 30 kilometres per hour. At night his speeding outline would glow with phosphorescence from plankton in the water. He became so famous that his picture featured on the cover of the Illustrated London News. It was never established whether ‘Jack’ was male or female.