19 December 2023

by Nathan Angelakis, PhD candidate with the University of Adelaide

When I was a teenager, working on beautiful islands, studying and learning about the ocean and marine life is something I dreamt about doing as a career. Throughout the course of my PhD it has felt incredibly surreal to see those dreams realised. My PhD project is focused on identifying and mapping critical habitats and foraging behaviours for the endangered Australian sea lion (Neophoca cinerea). By combining video collected from underwater cameras attached to Australian sea lions with their movement and diving behaviour, we are gaining an intimate view into how Australian sea lions forage across the continental shelf waters of southern Australia.

Nathan Angelakis monitoring Australian sea lions at Seal Bay Conservation Park on Kangaroo Island. Image: Roger Kirkwood

In the past 40 years Australian sea lion populations have declined by more than 60%. The species is currently listed as endangered by both the International Union for Conservation of Nature (IUCN) Red List of Threatened Species and under Australian legislation. Australian sea lions are benthic predators (forage on the seabed), while previous research has uncovered fundamental information on their foraging ecology, diet and diving behaviour, our knowledge of what habitats are critical to Australian sea lions is poor. Across the distribution of Australian sea lions, there are marked differences in the abundance and trends of populations. These differences suggest that threats to sea lions vary across small spatial scales. Identifying habitats and areas that are critical to Australian sea lions is hence key to assessing risks to populations and supporting future conservation/management actions to recover the species.

Above and below: Sea lions are sedated, anaesthetised and fitted with a satellite-linked GPS tag, underwater camera and an accelerometer/magnetometer. These are removed after a single, two to five day foraging trip. Images: Roger Kirkwood.

Through our amazing footage (see ABC story and video:
SARDI researchers take ocean ride with endangered seals through ‘sea lion cam’ we have discovered Australian sea lions foraging across diverse seabed habitats, including kelp reefs, seagrass meadows, sponge gardens and expansive sand flats. Sea lions also use a range of specialised foraging strategies to exploit a variety of prey (including fish, cephalopods, sharks and rays) and different benthic habitats. We have also been fortunate enough to capture footage of an adult female taking her pup to sea, providing the first evidence we have that Australian sea lion mothers use social learning to pass on foraging skills to pups. On top of this, we have caught glimpses of novel encounters with other marine predators, including sharks, dolphins, and rays. The opportunities for application of these data extend beyond just understanding the lives of sea lions as well, providing new information on the distribution of seabed habitats and other key marine species across the continental shelf waters of southern Australia.

When we recover a camera off an animal and download the video it has recorded, it is amazing to watch for the first time. With each animal we are learning something new about their behaviour. Sitting through hours and hours of video, every time an animal dives back down to the bottom, I am never certain what I am going to see next!

The data we have collected is allowing us to identify and map benthic habitats that sea lions use across the continental shelf and examine differences in foraging behaviour/strategies and prey preferences between individual sea lions and colonies. This information is key to advancing our understanding of Australian sea lions, assessing potential threats to populations, and supporting meaningful conservation and management of the species into the future.

I am very grateful to all the people and groups that have made this PhD possible. This includes the South Australian Research and Development Institute (SARDI Aquatic Sciences) and the University of Adelaide and my supervisors Prof. Simon Goldsworthy and Prof. Sean Connell. This project also would not have been possible without the Ecological Society of Australia and National Environmental Science Program (NESP) Marine and Coastal Hub. I also owe large thanks to Dr Roger Kirkwood, Dirk Holman, Mel Stonhill and the Department for Environment and Water and the Far West Coast Aboriginal Corporation.

The opportunities I have had throughout my PhD to camp on a beautiful, remote island, work hands-on with such a unique and charismatic species and make new discoveries about the marine world is something I am incredibly grateful for and brings me a lot of purpose. With future camera deployments on Australian sea lions, I am very excited for all that we still have to discover about this amazing species!

This article was first published by the Ecological Society of Australia. Nathan Angelakis was awarded a Holsworth Wildlife Research Endowment grant to help support this research.   

Australian sea lion pup at Olive Island in South Australia. Image: Nathan Angelakis