Dolphins: Perth's Marine Mammals and Their Fascinating Lives
Dolphins, the intelligent and loyal creatures of the sea, have a unique story to tell, especially those residing in Perth's waters.
These dolphins have a taste for what's in season, adapting their diet to the changing environment. But here's where it gets controversial: they're also loyal to their communities, yet occasionally venture out, almost like exploring nomads. And this is the part most people miss - they can survive shark bites, a testament to their resilience.
Dr. Delphine Chabanne, a passionate researcher from Murdoch University's Harry Butler Institute, has dedicated over a decade to studying these marine mammals. Her name, a delightful coincidence, is derived from the Latin word for 'dolphin' - 'Delphinus'.
In a recent presentation to students as part of the Thinking Blue program, Dr. Chabanne shared insights about Perth's coastal dolphins. She revealed that there are three species of coastal dolphins in Western Australia, with the Indo-Pacific bottlenose dolphins being the only species present in Perth.
"There are approximately 120 dolphins primarily residing in Cockburn Sound and Owen Anchorage, with an additional 25 utilizing the Swan Canning estuary," she explained.
Interestingly, there have been observations of dolphins from the Swan Canning estuary mingling with their Cockburn Sound counterparts, potentially for mating purposes. Dr. Chabanne highlighted an example of a dolphin named 'Hugs', born to a resident mother in Owen Anchorage, who has spent most of her time in the lower reaches of the Swan Canning estuary since having her first calf in 2021.
Studying Dolphins: A Challenging Yet Rewarding Endeavor
Dr. Chabanne's research involves boat surveys, where researchers zigzag or travel in parallel lines to spot dolphin groups. Once located, they photograph the dolphins, record group compositions, and monitor their behavior. Environmental conditions, such as water temperature and depth, are also noted when possible.
"We focus on the dorsal fins, as each is unique. Dolphins are born with smooth fins, but over time, they develop nicks, scars, and notches, allowing us to identify and track them," she explained. Since 2011, Dr. Chabanne's team has been issuing a 'Finbook' on the River Guardians website to help identify local dolphins residing in the Swan Canning estuary.
Dolphins, while resilient, can suffer from larger injuries, such as shark bites. Dr. Chabanne emphasized that dolphins are generally unaffected by shark bites unless they are bitten on their softer bellies, where vital internal organs are located.
Seasonal Diet and Threats to Dolphins
Perth's dolphins are opportunistic eaters, with their dietary preferences changing with the seasons. In summer, they tend to feast on benthic detritivore fish, like mullet, while in winter, they prefer cuttlefish and octopus. Despite having teeth, dolphins often toss octopus into the air to break it into smaller pieces before swallowing.
One of the biggest threats to dolphins is fishing gear, such as lines and nets, which can entangle 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, and loud noises underwater can disturb their behavior, as they rely heavily on sound.
Keeping the waterways clean and pollution-free is crucial for their overall health. Cetacean Morbillivirus, which weakens dolphins' immune systems, has claimed the lives of several dolphins around Perth. In 2009, six dolphins were found dead, with some infected by the virus, and another five died in 2019.
Interesting Dolphin Facts and How to Protect Them
Female dolphins can live up to 40 years, while males live around 35 years. They emit clicking sounds and listen to the returning echoes, using sound waves to understand their surroundings and search for food. Dolphin pregnancy lasts 12 months, and calves stay with their mothers for 3 to 5 years to learn essential skills.
One of the most fascinating facts is that dolphins rest half of their brain at a time, allowing them to stay alert for predators or danger and to surface for air.
To protect these magnificent creatures, here are some simple yet effective measures:
- Keep the oceans, estuaries, and coasts clean and tidy.
- 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 to maintain their natural diet.
- Join citizen science programs to contribute to dolphin research and conservation.
For more information on the Harry Butler Institute's Centre for Sustainable Aquatic Ecosystems at Murdoch University, visit their website. This article was authored by WAMSI and is reproduced with their permission. Photo courtesy of WAMSI.
Let's continue the conversation! What are your thoughts on these fascinating creatures and the measures we can take to protect them? Feel free to share your insights and experiences in the comments below!
