Around 90 to 120 Indo-Pacific bottlenose dolphins live permanently in the waters of Port Stephens within the Port Stephens – Great Lakes Marine Park, making it one of the most popular places in the world for dolphin watching.
The dolphins are a much loved resident of this beautiful area with visitors coming from all over the world eager to catch a glimpse of the dolphins playfully going about their day to day lives!
The rocky coastal headlands and long white beaches of Port Stephens provide an ideal vantage point for watching dolphins from the shore, or you could join one of the popular dolphin watch cruises that are on offer daily.
Port Stephens is part of the traditional country of the Worimi Aboriginal people, who have lived in the area for thousands of years, and have a special connection with the landscape, plants and animals.
Worimi people are spiritually connected to dolphins, or guparr, as they are called in the Gathang language. Traditionally elders would speak with dolphins about food resources and looking after each other.
Some elders still speak with dolphins today.
What is a bottlenose dolphin?
Bottlenose dolphins are a small cetacean belonging to the group of ‘toothed’ whales (Order Cetacea: Suborder Odontoceti).
They get their name from their short rounded snout or beak, that resembles a ‘bottle’. Oceanic dolphins belong to the Family Delphinidae.
What do bottlenose dolphins look like?
Bottlenose dolphins are sleek and streamlined with a prominent, broad, triangular dorsal fin located in the middle of the back. They vary in size, shape and colour and are generally dark on the back and have a light grey/white underside. This colouration assists in camouflaging them from their predators (sharks and killer whales). Looking up from below, the light underside of a dolphin blends against the sky and from above the dark back merges with deep water below. As dolphins get older they may develop a white spot on their bottlenose.
A huge variation in weight has been recorded, with dolphins ranging in size from 90 kg to 650 kg. However, the average weight is around 200 kg .
Do dolphins drink?
Ocean water is too salty for dolphins to drink, so they obtain their water needs from their food (fish and squid). Water is also released within their body as they metabolise (burn up) their fat, and their kidneys are adapted to conserving water. Although they live in a watery environment, dolphins live as desert animals with no direct source of drinking water.
Do dolphins sleep?
A dolphin cannot sleep like we do as it must remain awake to surface and breathe. Scientists have conducted studies and have found that dolphins close down one half of their brain at a time and ‘sleep’ in this way for up to eight hours a day. When a dolphin is ‘sleeping’ it will either swim slowly and occasionally surface to breathe, will rest at the surface with blowhole exposed, or will rest on the bottom in shallow water and surface occasionally to breathe.
How does a dolphin swim?
Bottlenose dolphins are sleek and streamlined and can travel up to 35 km/hr. Dolphins move their flukes (the lobes of the tail) up and down to go forward, with the pectoral flippers (at the sides) used for steering. The flukes and the dorsal fin are composed of connective tissue, only the pectoral fins contain bones. These bones are similar to the forelimbs of land mammals including those in your hand!
Dolphins have a horse-shoe shaped double-slit pupil which enables very good eyesight above and underwater. They also have good vision in low light.
Can dolphins smell?
Dolphins have little or no sense of smell because the blowhole (a dolphin’s nose) is closed underwater. Unlike humans, dolphins do not have olfactory nerves or a lobe in the brain associated with the sense of smell. They compensate for this loss with a very sensitive tongue which has taste buds that can distinguish different chemicals in their environment.
Can dolphins hear?
Dolphins have a sharp sense of hearing. Scientists believe that sound waves travel through the water, through the dolphin’s lower jaw to the inner ear and onto the brain for processing.
The dolphin’s breeding cycle
The bottlenose dolphins in Port Stephens have a long adolescence and the timing of breeding varies, according to geographic location. Females do not breed until they are 9–10 years of age and males 10–13 years. Male and female dolphins have genital slits on the underside of their bodies, so mating takes place belly-to-belly. The gestation period averages 12 months – a long time when compared to that of a humpback whale, which has an 11-month gestation to produce a 4.5 m calf. These dolphins have most of their calves during the summer months from December to March. The birth usually takes place in shallow water and the calves are assisted to the surface by their mothers to take their first breath. Dolphins are mammals, which means they are warm-blooded and suckle their young.
How do dolphins breathe?
Like all whales, bottlenose dolphins have lungs and breathe air- just like you do! A dolphin must surface to breathe through the blowhole on the top of their head usually diving for periods of 1 to 4 minutes. It takes a dolphin about one-fifth of a second to complete a full breath (to exhale and inhale) and dolphins can hold their breath for up to 20 minutes!
How long can dolphins live?
The maximum life expectancy of a dolphin is approximately 30 to 40 years.
Getting to know the Port Stephens Dolphins
Three different types (or species) of dolphins inhabit the waters in and around Port Stephens. The most common dolphin species within Port Stephens and just outside the Heads is the Indo-Pacific bottlenose dolphin (Tursiops aduncus). These are the dolphins you are most likely to spot if you are visiting the area and are common in shallow coastal waters of the Indian and Western Pacific oceans. Outside the Heads and along the open coastal beaches north and south of Nelson Bay, Common dolphins (Delphinus delphis) and the Common bottlenose dolphin (Tursiops truncatus) are often encountered.
How do we know Port Stephens bottlenose dolphins are special?
Scientific research conducted over the past decade by Macquarie University in partnership with the Port Stephens Dolphin Watch Association, NSW National Parks and Wildlife Service and the Marine Park Authority, has found that the bottlenose dolphin population living in Port Stephens is unique and genetically different from populations of Indo-Pacific bottlenose dolphins found elsewhere. They are even genetically distinct from dolphin communities that live on the coast between Newcastle and Forster!
Important research has also studied the interactions between dolphins and the dolphin-watching industry to gain a better understanding of potential impacts.
Adult Indo-Pacific bottlenose dolphins generally reach between 2–4 m in length.
In Port Stephens adult Indo-Pacific bottlenose dolphins generally reach between 2–3 m in length. New-born calves are usually less than 1m in length.
Between 90 to 120 individual dolphins live Port Stephens year round, this number can change between seasons and years.
A study carried out by Macquarie University researchers found that Port Stephens’ dolphins sometimes travel outside of the ‘Heads’ but the Dolphins in the eastern section of Port Stephens are often seen off Shoal Bay beach.
Port Stephens Dolphins seldom interbreed with dolphins that range on the coast between Newcastle and Forster. As a result, the Port Stephens population is genetically distinct and has a smaller gene pool than the larger coastal population. This is very surprising as dolphins can swim over a hundred kilometres a day, but the distance from Port Stephens to the Broughton Island dolphin community is only about 20 km.
The genetic distinctiveness of the Port Stephens population is likely caused by the uniqueness of the environment and the preferences of females to remain in the areas in which they were born. When females are familiar with their environment they can locate food more easily and therefore have greater success raising their calves. Females also rely on the females they have grown up with, to help them protect their calves from shark attacks and aggressive male dolphins.
Since the dolphins within Port Stephens are genetically distinct and are highly dependent on their environment, they may not be as resilient to changes in their environment and to high levels of human activity, compared with larger dolphin populations (such as dolphins in Shark Bay, Western Australia).
For this reason, as a community, we need to look after our dolphins.
The Dolphin and Whale Watch Nelson Bay Team