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From above, the fishing rope cutting into the fur seal’s chunky neck looks for all the world like a fat roll on her generous body. On researcher Adam Yaney-Keller’s thermal camera, the seal’s injury is unmistakable – its heat is generating a glowing line on his screen.
The scale of fishing debris is vast and growing, as marine heatwaves push both fish and fishers closer to coastlines where seals, fur seals, walruses and sea lions congregate.
That’s where technology such as drones equipped with thermal cameras comes in.
Yaney-Keller, a PhD candidate at Monash University, has spent the past few years using drone-borne colour cameras and thermal infrared imaging to detect fur seals that have been entangled in marine debris – often fishing ropes and netting.
But identifying a single injured animal in a larger group – particularly in a colony – presents overwhelming logistical difficulties.
Added to the practical difficulties are more ethical ones. Yaney-Keller and a team from Monash University and Phillip Island Nature Parks have conducted dozens of trips to Seal Rocks, off the coast of Phillip Island.
The Victorian island is host to the largest colony of Australian fur seals, where it is estimated 19,000 seals live, and researchers walking through the colony run the risk of disturbing nursing mothers, scaring off young, or encountering protective and aggressive males during mating season.
For these reasons, researchers now hang back and let their drones do the searching.
Yaney-Keller says that given the sheer number of fur seals at Seal Rocks, they almost always find an entanglement when they send their technology into the sky.
“The seas are full of plastic and things that these animals can get caught up in,” he said. “All this marine debris pollution coming from either fishing vessels or coming just from land inputs or just our normal trash, the animals can get caught in nearly anything.”
Over the past few years, researchers have rescued more than a dozen fur seals from entanglement.
They tracked one, a juvenile, for eight months before they could catch her and remove the green fishing net slowly strangling her as she grew.
“We were able to see that after we disentangled her, she did some big foraging trips, and she started to recover a lot better. It was really nice to see that, from this sort of injury, that can be quite horrific, that you can make a real difference if you just take it off of them.”
An unexpected bonus from the research was the discovery that shark bites and other injuries are also visible from the air, raising hopes of more targeted rescues and rehabilitation attempts.
Phillip Island Nature Parks marine scientist Dr Rebecca McIntosh said the use of thermal drones to scan fur seal colonies was a major breakthrough for conservation.
“This technology allows us to see subtle heat signatures that reveal injuries and entanglements from the air that can normally be difficult to see,” McIntosh said.
“It means we can detect at-risk seals earlier, intervene with better information and ultimately improve welfare outcomes for individuals and better understand trends in entanglement and impacts on the population as a whole.”
While all marine animals are at risk of entanglement, fur seals and other pinnipeds – including seals, sea lions and walruses – are a barometer for the plastic problem affecting the broader marine environment because they spend so much time on land.
Yaney-Keller said people could help reduce the problem of entanglements by avoiding fishing in areas known to be populated by seals.
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