Sky-high science helps endangered sea lions
A quest to count vulnerable Australian sea lion pups using a remotely piloted aircraft (RPA), commonly known as a drone, in the Great Australian Bight has produced the most precise population survey to date. Sea lions breed and rest along the coast in this region and these inshore areas are managed as part of the Far West Coast state marine park. To feed, the sea lions ravel offshore into the Great Australian Bight Marine Park which is recognised as supporting important foraging grounds for this species.
The trial RPA-based monitoring technique — funded in partnership with Parks Australia and involving RPA consultancy Global Unmanned Systems and local Natural Resources Eyre Peninsula staff — has allowed researchers to visually access and generate maps for highly inaccessible sea lion colonies that were previously near-impossible to monitor.
State Marine Park Manager Dirk Holman said monitoring Australian sea lion colonies using a RPA ensures safer viewing of inaccessible and actively crumbling rock platforms at the bottom of the Bunda Cliffs.
“For the first time we are able to see near-entire colonies,” Mr Holman said.
“We have reviewable data which can be interrogated more accurately than the previous methods, which involved using binoculars and cameras from the clifftop. The information gathered and created by the RPA, along with associated mapping of the Bunda Cliffs, has allowed us to visually ‘capture’ more animals in each colony, giving us a better understanding of the populations.”
Australian sea lions (Neophoca cinerea) are the least abundant of seal species in Australia. They are listed as vulnerable to extinction under national and state legislation, and endangered under the International Union for the Conservation of Nature Redlist.
“Reviewing the latest survey count, across the three RPA surveys in winter 2017, we were able to see an increase in total animals per colony of 283 per cent. There was also a 385 per cent increase of average pups per colony. This is not due to a population recovery, but being able to visually access the entire colonies for the first time,” Mr Holman said.
“While this method works in this area, traditional survey methods are still appropriate in other locations. I see its value as an important tool which we can use to complement existing survey methods at certain colonies across the state.
“It provides an additional benefit of producing photo imagery which can in turn be used to produce both 3D models and photo mosaics which can be used to measure changes in colony populations across time.”
Manager of Global Unmanned Systems Rob Lednor also said the nature of the place , the high cliffs, strong winds and almost permanent shadow did present a few challenges.
“The Bunda cliffs reach a scale of approximately 100m and this rough, steep landscape is often battered by strong winds blowing in from the Southern Ocean,” he said.
“Conditions are challenging for RPA operators and the equipment, especially in the context of conducting fauna surveys. The sea lions are right at the base of the cliffs so we had to adapt to working in an almost permanent shadow cased by the southern-facing aspect of the cliffs.
“We use small multi-rotors with high-quality cameras. This enables us to fly the RPA below the operator, acquiring high resolution imagery at regular intervals across the extent of habitable area.
“These high-resolution images are captured in quick succession, enabling experts to review the imagery post-flight and conduct fauna counts. Recent advances in image analysis techniques and artifical intelligence (machine-learning) present further opportunities to bring cutting-edge innovation to marine parks management, something the marine parks team and Global Unmanned Systems are actively exploring.”
In future Natural Resources EP hopes to apply the technology to other suitable sea lion colonies on islands within the Spencer Gulf and off the west coast of Eyre Peninsula.
To read more please visit: parksaustralia.gov.au/marine/parks/south-west/great-australian-bight/#australian-sea-lions
Additional: Did you know Australian Sea Lions have a breeding cycle which lasts approximately 17.5 months, unlike similar animals which have an annual breeding cycle? Breeding cycles amongst colonies are asynchronous, meaning colonies can breed out of phase temporally with other colonies, even those in close proximity to each other. It is believed there is little to no exchange of breeding females between colonies, which results in each colony being a closed population, making small colonies vulnerable to collapse.