Dolphins are amazing… and we need them!

Dolphins are seen by most people as charismatic animals. They amaze us with their intelligence, their grace, their acrobatic skills and with their ability to play and interact with human kind sometime. But what we see is just a tiny part of the dolphin’s world. Most of their world is underwater and beyond what we are capable of perceiving. Dolphins play an important role in the whole marine eco-system.

1. Dolphins help keep their environment in balance : they are predators - eating mainly fish and squid - but they are also prey to bigger predators such as shark, and killer whales. Without dolphins the natural balance that exists in the food chain would be disrupted and would ultimately affect other wildlife in the ocean.

2. Dolphins act as bio-indicator, according to the Institute of Marine Mammals. By monitoring dolphins in their environment, we can find out if something is going wrong ( like water pollution) in the ocean. Therefore, dolphin studies help protect other marine wildlife and humans as well since we eat some of the same food.

3. Dolphins often prey on ill or old fish. By doing so, dolphins help stop the spread of infectious diseases among fish populations. This keeps more fish species healthy and alive to reproduce. For example, dolphin may eat fish poisoned by ciguatera (a toxin affecting humans but not dolphins). Since humans can be food-poisoned by ciguatera, dolphins help keep infected fish off the table!

Dolphins are precious allies to other species and us, humans. Without dolphins, there would be more disease and lower fish populations in the ocean. We need to protect them, not just because we love them, but also because we need them 😊

 

Dolphins in New-Zealand

There are 9 different species of dolphins found around New-Zealand. The smallest and rarest dolphin is the Hector/Maui dolphin. Here is a description of this very precious dolphin, followed by a description of the other species found in NZ waters.

 

Hector’s dolphin/Tupoupou (Cephalorhynchus hectori hectori)

Conservation status : nationally endangered

Named after James Hector who is believed to be the first person to have thoroughly examined this species.

Grey with black and white markings and a round dorsal fin, the Hector’s dolphin is easily recognised.

Endemic of New-Zealand, Hector’s dolphin is among the smallest marine dolphins in the world, reaching 1.5 meter long at maximum and weighing between 40-60 kg. Male are slightly smaller and lighter than female.

There are 2 sub-species :

• the South Island Hector’s dolphin found around the South Island and
• the Maui dolphin/popoto (Cephalorhynchus hectori maui) found off the West coast of the North Island.

The Maui dolphin is even more endangered (Nationally critical) than the Hector’s dolphin due to its very small population.

Photo by Mark Kitchingman

What do Hector dolphins eat?

Hector dolphins eat fish, squid and crab. Their diet is believed to be more influenced by the size of the prey rather than the type. They hunt in pods of up to 8 dolphins. Like the other species of dolphins, Hector’s dolphin use echolocation to find their prey : they produce high frequency “clicks” that bounce off objects and animals and give them a picture of what surround them.

Social behaviour

Hector’s dolphins usually travel in small pods of up to 5, although can be seen in larger pods (20 or more) especially during mating period.

They communicate using clicks and whistles and interact in different ways such as chasing each other, leaping out of the water, blowing bubbles and playing with seaweed.

Hector’s dolphins are known to be very curious species approaching and swimming near boats.

Dolphin leaping out of the water

Breeding

Hector’s dolphin mate around the summer months, the gestation period is 10-11 months. They reach sexual maturity between 5-9 years, females being mature later than the males.

Each female gives birth to a calf only every 2 to 3 years - which makes their population increase at very slow rate - and produce only 4 or 5 calves in a lifetime. Calves stay with their mother for up to 2 years.

Hector’s dolphins live to around 20 years of age.

Threats

Their conservation status is nationally vulnerable (critical for the Maui dolphin), with a decreasing population.

Natural predation of Hector’s dolphins includes sharks and killer whales (orcas).

Human threats to the Hector dolphin include fishing methods, oil and gas exploration, boat strike, mining, tourism, noise…

A major threat for Hector’s dolphins (and other dolphins) is set net fishing. Dolphins can get caught in the net, then not able to come back to the surface to breathe air (remember, dolphins are mammals therefore have lungs and need air to survive) they sadly die drowning or suffocating. Dolphins can also be killed or harmed by boats.

Due to pollution, boating, fishing and recreational activities over the past 30-40 years, the population of dolphins has significantly reduced from 26,000 to less than 14,000.

Despite actions made toward the protection of Hector’s and Maui dolphins, dolphins are still found caught in nets and accidentally killed by boat and might face extinction is no further/better protection is made to support their survival.

A Hector dolphin's calf killed by a propeller. Photo Al Hutt

Hector dolphin tangled in net. Photos by Department of Conservation

Some very sad discoveries that could be avoided with a better Threat Management Plan?

 

Other species of dolphins in NZ include :

Dusky dolphin (Lagenorhynchus obscurus) :

Conservation status : Not theatened

Found around NZ mainly South of East Cape but also around South America, off south eastern Africa. In New-Zealand the main population are found in Kaikoura and Admiralty Bay. There are thought to be between 12,000 and 20,000 Dusky dolphins in New-Zealand.

Picture by International Whaling commission

Bottlenose dolphin/Terehu (Tursiops truncatus)

Conservation status: Nationally endangered

Bottlenose dolphins are widely distributed throughout the world in cold temperate and tropical seas. New Zealand is at the Southern most point of their range. Limits to the range of this species appear to be temperature related.

Bottlenose dolphins are found both offshore ad in many enclosed areas such as the Mediterranean, Black ad Red Seas.

In New Zealand 3 main coastal populations exist:

• Around 450 individuals live in the North Island area. There are currently 96 individual dolphins visiting the Bay of Islands area
• Around 63 live in Doubtful Sound, Fiordland (as at 1998)
• Another group range from the Marlborough Sounds to Westport.

Picture by International Whaling commission

Common dolphin/aihe (Delphinus delphis):

Conservation status : Not threatened

Found in offshore warm-temperate waters in the Atlantic and Pacific, common dolphin is the most numerous dolphin within this range. It is closely related to the long-beaked common dolphin (Delphinus capensis) which prefers shallower and warmer water.

 

Short-beaked common dolphins are found in waters throughout New Zealand and Australia. In New Zealand, this species tends to remain a few kilometres from the coast and is particularly common in the Hauraki Gulf and off Northland.

Common dolphins may form enormous schools of several thousand individuals. They are also known to associate with schools of pilot whales and other dolphin species such as dusky dolphins. This species is abundant but precise population estimates are largely unknown.

Picture by International Whaling commission

Orca (killer whale)/maki (Orcinus orca)

Conservation status : Nationally critical

Despite its name Orca is the largest member of the dolphin family. There are an estimated 150–200 individuals in New-Zealand, which travel long distances throughout the country’s coastal waters.

Orca are typically encountered in family groups or pods. Pods are usually formed for life and can result in the development of unique dialects.

Picture by International Whaling commission

Pilot whale (Long-finned)/upokohue (Globicephala melas edwardii)

Conservation status : Not threatened

Pilot whales, despite their name, belong to the dolphin family. Male can grow over 6 meters in length, the female can reach 5 meters.

Long-finned pilot whales are found throughout the Southern Ocean. A sub-specie lives in the North Atlantic. They usually are occuring in groups of 20-50 individuals but larger herds of several hundreds have been seen.

Pilot whales like swimming in areas that are topographically "steep" (high relief, such as submerged banks and the edge of the continental shelf. Their preference for steep landforms may partially explain their tendency to strand – their sonar may not function so well in the shallow, gently sloping underwater environments that are typical of high-stranding areas such as Golden Bay.

Picture by International Whaling commission

 

What can you do to help dolphins?

(ref. Department of conservation)

Report your sighting : If you are in the North Island and think you’ve seen a Māui or Hector’s dolphin, report it straight away to our emergency hotline 0800 DOC HOT (0800 362 468). Include as much information as possible with your sighting:

• the date, time and location (GPS coordinates if possible)
• the number of dolphins and estimated sizes
• the direction they were travelling
• take photographs or video if possible.

You can also choose to join some of the many operators like ourselves that have voluntarily signed up for the DOC SMART accreditation which encourage education by exemplary good behavior around marine mammals. So if you consider joining a harbour cruise or a sea-kayaking tour look for this extra logo and support those who wants to make a difference.


How to approach dolphins

From a boat:

• carefully approach dolphins from their side and slightly to the rear.
• operate your boat slowly and quietly at ‘no wake’ speed within 300 m.
• don't approach a group of dolphins if three or more boats are already within 300 m of the group.
• manoeuvre your boat carefully. Do not obstruct their path, cut through a group, or separate mothers from calves.

From a boat or swimming:

• avoid loud or sudden noises that could startle dolphins.
• don't swim with dolphins when calves are present.
• don't try to touch the dolphins or feed them.
• co-operate with others so all may see the dolphins without putting them at risk.

Call DOC's emergency hotline immediately 0800 DOC HOT (0800 362 468) and follow any instructions from DOC staff.
Prompt reporting increases the likelihood that we can save dolphins in distress and learn more about deceased dolphins, including conducting necropsies in some situations to identify the cause of death and to collect important scientific data that may help us manage threats to dolphins.