Dolphins in Perth: Unveiling Their Unique Lifestyle and Challenges
A Tale of Two Dolphin Communities
In the vibrant waters of Perth, two distinct dolphin groups thrive, each with its own story to tell. These dolphins, studied for over a decade by Dr. Delphine Chabanne, a passionate researcher from Murdoch University's Harry Butler Institute, showcase a fascinating way of life.
The Swan-Canning and Cockburn Sound Dolphins
Perth is home to the Indo-Pacific bottlenose dolphins, with approximately 120 residing primarily in Cockburn Sound and Owen Anchorage, and a smaller group of around 25 dolphins frequenting the Swan Canning estuary. While these groups generally stick to their own, there have been intriguing instances of intermingling and even potential mating between them.
The Journey of 'Hugs'
One notable example is 'Hugs', a dolphin born to a resident mother in Owen Anchorage. Since having her first calf in 2021, Hugs has primarily resided in the lower reaches of the Swan Canning estuary, showcasing the occasional movement between these dolphin communities.
Studying Perth's Dolphins
Dr. Chabanne and her team employ a unique approach to studying these dolphins. They navigate the waters in boats, searching for dolphin groups in parallel or zig-zag patterns. Once spotted, they photograph the distinctive dorsal fins, record group compositions, and monitor dolphin behavior. Environmental conditions, such as water temperature and depth, are also noted when possible.
The 'Finbook' Project
Since 2011, Dr. Chabanne's team has been maintaining a 'Finbook' on the River Guardians website, aiding in the identification of local dolphins residing in the Swan Canning estuary. Each dolphin's dorsal fin is unique, with smooth fins at birth that develop nicks, scars, and notches over time, providing a natural identification system.
Dolphin Diet and Resilience
Perth's dolphins are opportunistic eaters, with their dietary preferences shifting with the seasons. In summer, they tend to feast on benthic detritivore fish like mullet, while winter sees them favoring cuttlefish and octopus. Despite having teeth, dolphins often toss octopus into the air to break it into smaller, more manageable pieces before swallowing.
And here's where it gets controversial... Dolphins are known to be resilient to shark bites, but only if they're not bitten on their softer bellies, where their vital internal organs are located.
Threats to Dolphin Survival
One of the biggest dangers to dolphins is fishing lines and nets in the water, which can easily tangle them. Removing this gear is challenging, and due to their size, thinner blubber, and limited environmental awareness, dolphin calves are particularly vulnerable to entanglement. Boat strikes are another threat, as loud noises underwater can disturb their behavior, and pollution can impact their overall health.
The Impact of Cetacean Morbillivirus
This virus, which weakens dolphins' immune systems, has claimed the lives of several dolphins around Perth. In 2009, six dolphins were found dead, with some infected with the virus, and another five perished in 2019, highlighting the devastating impact of this disease.
Dolphin Life Facts
Female dolphins can live up to 40 years, while males typically live around 35 years. They navigate and search for food by emitting clicking sounds and listening to the returning echoes as sound waves bounce off surfaces.
Dolphin pregnancy lasts 12 months, and calves stay with their mothers for 3 to 5 years, learning essential survival skills.
And this is the part most people miss... Dolphins have an incredible ability to rest one half of their brain at a time, allowing them to stay alert for predators or danger while still surfacing for air.
Protecting Our Dolphin Friends
To ensure the well-being of these fascinating creatures, here are some key actions we can take:
- Keep our oceans, estuaries, and coasts clean and pollution-free.
- Organize beach clean-ups to prevent rubbish from entering the water.
- Dispose of fishing lines and gear carefully.
- Slow down when boating to avoid collisions.
- Refrain from feeding dolphins, as it can disrupt their natural diet and behavior.
- Join citizen science programs to contribute to dolphin research and conservation efforts.
Learn more about the Harry Butler Institute's Centre for Sustainable Aquatic Ecosystems at Murdoch University and explore the fascinating world of marine research and conservation.
This article was authored by WAMSI and is shared with their permission. Photo courtesy of WAMSI.
