Dr Krista’s Dolphin Diaries
We’re proud to be working alongside and learning from Dr Krista Nicholson as we deepen our understanding of Mandurah’s incredible dolphin community. Through her ongoing research in the Peel-Harvey Estuary, Krista has uncovered fascinating insights into the lives, behaviours, and challenges faced by these resident dolphins. To take you behind the scenes, she’ll be sharing her “Dolphin Diaries”, offering a closer look at the science, stories, and discoveries shaping their future. Here’s your first glimpse into her important work.
A Decade of Discovery: Understanding Mandurah’s Estuarine Dolphins
The Peel-Harvey Estuary in Mandurah hosts a remarkable resident community of Indo-Pacific bottlenose dolphins (Tursiops aduncus). For the past decade, I, Dr Krista Nicholson, have been conducting studies focussing on their ecology, social structure, and behaviour.
The shallow, micro tidal estuary has long been recognised as a dolphin live-stranding hotspot, with many individuals alive today bearing distinct white scars from past stranding. To better understand why dolphins strand here, it was important to first establish how many dolphins use the estuary and whether it is an important area for them. As such, from 2016 onward, boat-based surveys have been conducted in the estuary and adjacent coastal waters to collect photo-identification data and tissue samples, alongside detailed behavioural observations.
What we discovered was that the estuary supports a distinct, residential social community of approximately 90 dolphins who rely on the estuary for food. In contrast, four nearby coastal communities were also identified, which were socially and spatially distinct but isotopically similar to one another. Coastal dolphins periodically enter the estuary, particularly in the entrance channels during seasonal fish migrations, creating opportunities for interaction and potentially mating.
In the last decade, we have been able to obtain census-level data as our observations are complemented with those from Estuary Guardians and Mandurah Cruises. This has allowed us to estimate reliable reproductive and survival rates and understand the population structure of the estuarine community. The population was found to be relatively stable but with a slightly negative growth rate, making it vulnerable to external pressures. Importantly, we have never observed any immigration to the estuary, all individuals who are part of the community are born into it. While calf and juvenile sex ratios remain balanced, adult females continue to outnumber adult males likely due to patterns of emigration and death overtime. Reproductive output has been high, with all mature females producing calves every 2-4 years. Our work so far has provided for the dolphins to be recognised as components of the ecological character of the Ramsar-listed Peel-Yalgorup wetland system.
Going back to the standings, since 2016, 42 individuals have live-stranded with all but one of them being part of the estuarine dolphin community. While stranded, dolphins are at risk pf being sunburnt and their organs shutting down under pressure while they are not supported by water. Sadly, many of the resident dolphins have been lost due to live strandings.
To ensure better detection of stranded dolphins, part of our research currently focuses on how dolphins use the areas where they strand, and whether environmental conditions can predict when these live standings are likely to occur. This work, supported by Mandurah Cruises, will hopefully help in ensuring healthy dolphins that strand are found quickly and can be helped to deeper waters.
I look forward to sharing our research journey with you!
– Dr Krista Nicholson, Murdoch University
For more
We hope you’re enjoying learning about Mandurah’s dolphins and the research that helps us understand them. Keep an eye out for more of Dr. Krista’s Dolphin Diaries to continue learning about these incredible animals, coming soon!
Read more about our support for the Mandurah Dolphin Research Project here.
Delve deeper into Dr. Nicholson’s studies here.
If you’re feeling inspired, there are plenty of ways to get involved, from citizen science projects to volunteer programs and community initiatives, all making a real difference in protecting these iconic dolphins.
