Saving Tasmanian Wedge-tailed Eagle

Chris Johnson is an ecologist and Professor of Wildlife Conservation at the University of Tasmania. He says that 'one of the key challenges in the Tasmanian ecosystem, particularly over the last 100 years is we've been losing our big carnivores.'

This is a big problem because the decline of native carnivores means an increase in invasive species, which can have devastating impacts on Australian wildlife. Professor Johnson notes that this has happened before with the decline of the Tasmanian devil.

'As devils declined one of the species that benefited was the feral cat, because they scavenge on carcasses if they have the opportunity.'

'The Tasmanian wedge-tailed eagle is an important connector in the ecosystem. It's now one of the most significant species for essentially recycling the carcasses of animals that have died, of breaking down their bodies so they can be returned to the ecosystem,' says Professor Johnson.

'If we respect and even restore our native carnivores, we can protect biodiversity much better than if we spend all of our time trying to track cats or shoot foxes to get rid of them,' he adds.

As urbanisation and development increases in Tasmania, so do the number of risks and threats to wedgies. The apex predators travel long distances, and along the way, are prone to colliding with infrastructure like power lines and wind turbines. They're also particularly shy breeders.

'When they're at the nest trying to breed, it seems clear that they quite readily abandon breeding attempts if they get disturbed. The disturbance could be potentially quite subtle. Things like too much traffic close to a nest tree, where the traffic is the occasional timber trucks or too many people walking around making noise,' he says.

He says the project's guiding question is how can we ensure the coexistence of big predators that travel long distances within landscapes that people use for lots of different purposes?

'That's the most fundamental problem, and that's really important throughout the world.'

Professor Johnson says he is inspired by the recovery of wildlife in Europe, including landscapes that are highly modified and dominated by people.

'Wolves are increasing, lynx are coming back. Bears, wolverines and beavers are being intentionally reintroduced because they belong there and they have many, many benefits.'

He notes that in Australia, there have been a lot of changes in animal biodiversity. Though his previous research has primarily focused on mammals, he is ultimately trying to understand those threats and then develop strategies, planning tools and methods and concepts that we can use to protect threatened species.

'If we want to live in ecosystems that are healthy and functional, and where all of the ecological processes that are needed for ecosystem function are still operating, we need these big animals.'

Professor Johnson says a key problem is the lack of clear data about wedgies. Not just about their behaviour and the threats they face, but also about their numbers.

'Some of the estimates are as low as 500 breeding birds, which would be 250 breeding pairs, which is a pretty significant level of endangerment.'

'If you're down to that small number, it doesn't take very many deaths or disturbances to have a big impact on the rate of growth or replenishment. It's quite easy to tip it into population decline, but we don't exactly know.'

Through this ARC project, Professor Johnson and his team are filling this gap. His team utilises GPS tracking devices to track the movements of wedgies. This allows them to gain an in-depth understanding of wedgies' behaviour, and how they interact with their changing environment over time.

'The tags can take the location every 6 seconds, so the resolution of the data is actually phenomenal,' he says.

With this fine-grained data, his team can 'come up with some rules of operation for land use industries that will minimise their impact on eagles'.

A recent publication uses this data to map a model that can be used to predict the likelihood of collision of eagles with powerlines throughout Tasmania. 'There have been lots of collisions and deaths in the past and this helps to explain why those places are risky,' says Professor Johnson.

The project builds on the work of Dr James Pay, who tagged the birds during his PhD just over 5 years ago. Dr Pay is now a postdoctoral fellow on Professor Johnson's team.

'This is a long-term project,' says Professor Johnson.

'I came into it to help pull together some of the agencies and groups that James was working with, in order to get him a postdoctoral fellowship that would keep him going for another 4 years.'

'We thought we can use ARC funding to actually build a team and a group that has a bit of a life span.'

The team - which now includes 1 postdoctoral fellow, 3 PhD students, and a number of research assistants - works closely with 7 industry partners to ensure their learning is applied.

'I think this grant is extremely helpful for building a team and connecting up different organisations so that they can work together on a big project.'

The team also collaborates with a citizen science project, which involves hundreds of people who go out every year to do a count of wedgies using improved surveying methods. This helps provide further information about how many wedgies there are, as well as where they are.

Professor Johnson says the research methodologies his team is using can be applied all over the world.

'I think one role of a project like this is to just to mark out a pathway to say this is knowledge that we can use to make the world better, and to help these species survive without actually hurting human interests.'

'It's a way of reconciling animal interests with human interests.'