Imagine a world where dolphins are battling pollution, dodging boats, and struggling to find food. Sadly, this is the reality for Perth's beloved dolphins, but dedicated researchers are working tirelessly to understand and protect them.
For over a decade, Dr. Delphine Chabanne, a researcher at Murdoch University and a passionate advocate for these marine mammals, has been studying the two main dolphin groups in Perth: those in the Swan-Canning Rivers and those further south in Cockburn Sound. Dr. Chabanne's dedication is deeply personal; born and raised in France, she was named after the very creatures she studies (Delphinus is Latin for 'dolphin'). Her work, often supported by citizen scientist volunteers, provides crucial insights into the lives of these fascinating animals.
Dr. Chabanne shared her knowledge with students in late 2025 as part of the Western Australian Marine Science Institution's (WAMSI) Thinking Blue education outreach program, which connects students with leading researchers through online talks. You can learn more about the Harry Butler Institute at Murdoch University here: (https://www.murdoch.edu.au/research/hbi).
"In Western Australia, we have three species of coastal dolphins, but around Perth, we primarily see the Indo-Pacific bottlenose dolphin," Dr. Chabanne explained. "We estimate about 120 dolphins reside mainly in Cockburn Sound and Owen Anchorage, while around 25 regularly use the Swan Canning estuary."
These dolphin communities aren't always isolated. "We sometimes observe dolphins from the Swan Canning estuary mingling with those from Cockburn Sound, potentially for mating purposes," Dr. Chabanne noted. But here's where it gets controversial... Is this intermingling a healthy sign of genetic diversity, or does it indicate that one group's territory is shrinking due to environmental pressures, forcing them to seek resources elsewhere? What do you think?
"While rare, movement between communities does happen. For example, there's 'Hugs,' born to a resident mother in Owen Anchorage. Since having her first calf in 2021, she's spent most of her time in the lower reaches of the Swan Canning estuary." This behavior raises fascinating questions about dolphin social structures and adaptability. What factors influence a dolphin's decision to relocate, and how does it impact the existing community?
How are these dolphins studied, anyway?
Dr. Chabanne described the meticulous process of dolphin surveys. Researchers travel by boat, following parallel lines or a zig-zag pattern, carefully scanning for groups of dolphins. Once spotted, they document everything: taking photographs, recording the group's composition, and observing the animals' behavior. They also collect environmental data, such as water temperature and depth, whenever possible.
"We photograph their dorsal fins because each one is unique," Dr. Chabanne explained. "Dolphins are born with smooth fins, but over time, they accumulate nicks, scars, and notches that act like fingerprints, allowing us to track individuals."
Since 2011, a 'Finbook' has been available on the River Guardians website, aiding in the identification of local dolphins residing in the Swan Canning estuary. Using this resource, citizen scientists can contribute to ongoing research by reporting sightings and helping to monitor the dolphins' well-being.
Sometimes, these fins bear witness to more serious encounters. "Dolphins occasionally have larger injuries, such as shark bites," Dr. Chabanne mentioned. And this is the part most people miss... Dolphins, despite their playful nature, live in a world filled with real dangers.
Generally, dolphins are resilient to shark bites, unless the bite occurs on their vulnerable bellies, where their vital organs are located. This highlights the constant threat these animals face in their natural environment.
Seasonal Dining: A Dolphin's Diet
Perth's dolphins are opportunistic feeders, meaning they adapt their diet to what's readily available. Dr. Chabanne explained that their preferences change with the seasons. In summer, they tend to eat more benthic detritivore fish, such as mullet, which feed on organic matter at the bottom of the waterways. In winter, they prefer cuttlefish and octopus. Although dolphins have teeth, they often toss octopus into the air to break it into smaller pieces before swallowing them. This clever feeding strategy demonstrates their intelligence and adaptability.
Threats to Dolphin Survival
"One of the biggest dangers is fishing lines and nets in the water, which can entangle dolphins," Dr. Chabanne warned. "Removing the gear can be very difficult, and because of their size, thinner blubber, and limited awareness of their environment, dolphin calves are particularly vulnerable to fishing gear entanglement." This is a stark reminder of the impact human activity can have on marine life.
Boat strikes are another significant threat. Because dolphins rely heavily on sound for communication and navigation, loud underwater noises can disrupt their behavior and even cause physical harm. The delicate balance of their ecosystem is easily disturbed by human interference.
Keeping waterways clean and free of pollution is also crucial for their overall health. "Cetacean Morbillivirus, which weakens the animals' immune system, has killed dolphins around Perth. Some of six dolphins found dead in 2009 were infected with the virus, and another five died in 2019." This devastating disease outbreak underscores the importance of maintaining a healthy aquatic environment.
Intriguing Dolphin Facts
- Females can live for about 40 years, while males typically live around 35 years.
- They use echolocation, emitting clicking sounds and listening to the returning echoes to understand their surroundings and find food. It's like having a built-in sonar system!
- Dolphin pregnancy lasts approximately 12 months, and calves stay with their mothers for 3 to 5 years, learning essential survival skills. This extended period of maternal care highlights the importance of family bonds in dolphin society.
- Dolphins rest one half of their brain at a time, allowing them to stay alert for predators or danger and to surface for air. This remarkable ability allows them to maintain vigilance even while resting.
How Can You Help Protect Perth's Dolphins?
- Keep oceans, estuaries, and coastlines clean and tidy. Even small actions can make a big difference.
- Organize or participate in beach cleanups to prevent rubbish from entering the water.
- Dispose of fishing line and other gear carefully to avoid entanglement.
- Slow down when operating boats in areas where dolphins are present.
- Never feed dolphins, as this can disrupt their natural foraging behavior and make them dependent on humans.
- Join a citizen science program to contribute to dolphin research and conservation efforts.
Find out more about the Harry Butler Institutes' Centre for Sustainable Aquatic Ecosystems at Murdoch University (https://www.murdoch.edu.au/research/hbi/centres/centre-for-sustainable-aquatic-ecosystems).
So, what are your thoughts? Are we doing enough to protect Perth's dolphins? What other measures could be implemented to ensure their survival for future generations? Share your opinions in the comments below!
This article was authored by WAMSI (https://wamsi.org.au/news/perths-dolphins-eat-whats-in-season-and-are-loyal-to-their-groups/) and is reproduced with permission. Photo courtesy of WAMSI.
