In short:
Researchers use thermal drones in the Daintree to spot the highly elusive Bennett's tree kangaroos which live in treetops.
The animals haven't been surveyed for many years and much is still unknown about their population, life cycle, and behaviour.
What's next?
Researchers hope to get to know more about the animals.
In dense rainforest canopy, a small fuzzy head followed by an enormous tail pokes through leaves.Â
As the black and white image sharpens it reveals a Bennett's tree kangaroo, Dendrolagus bennettianus, an elusive marsupial native to Australia.
One of Australia's two tree-kangaroo species, the Bennett's is listed as Near Threatened on the IUCN Red List but has not been assessed for 10 years.
It was frustration at never being able to spot the animals which led PhD candidate Emmeline Norris to use a thermal drone camera to discover things previously unknown about these shy creatures.
The James Cook University student said much about Bennett's tree kangaroos remains unknown, including their diet or how they might respond to climate change.
Looking from above
The Daintree Rainforest is famously dense, which Ms Norris said makes searching for arboreal wildlife quite challenging.
Bennett's tree kangaroos can be incredibly difficult to spot from both the ground and above. (Supplied: Emmeline Norris, James Cook University)
She said spotlighting — using a torch to look for animals' eye shine — and using thermal cameras from the ground were the typical ways researchers would look for them.
But by observing the animals from the sky they have been able to see more.
Ms Norris said the animals seemed largely not bothered by the drones as they are seen eating vines and observed in their social interactions.
It's important to chose a time of day when trees are cooler to create a better contrast between them and marsupials. (Supplied: Emmeline Norris, James Cook University)
She said males were often solitary, but sometimes the researchers saw groups of two or three of the animals together.
"We think that might be either an adult female with last year's young, and maybe this year's young," she said.
"Or it could be a female, her young, and another male who's come to try and win her over."
She said being able to monitor the population is the first step to being able to detect any declines.
Pros and cons
Ecology professor at Queensland University of Technology, Grant Hamilton, has also used drones to monitor animal populations in separate studies, including koalas and deer.
He said this new development was "incredibly exciting".
"Once you break that first barrier … you make it a foundational technique,"
he said.
"Then what you can do is really start planning out how to do this in a systematic way so that we can track changes through time."
Professor Hamilton said drones have allowed researchers to cover much greater areas with better accuracy.
The marsupials are arboreal and have evolved to use their large tails to help with climbing. (Supplied: Emmeline Norris, James Cook University)
Researchers have made use of another technology such as machine-learning algorithms to help sort through the sheer amount of data they've been able to collect with the drones.
Professor Hamilton said it was important to remember the environmental information that "boots on the ground" can deliver, as well as the logistical challenges of drone flight.
"In general you need line of sight, so you need to be up high enough to be able to see the drone operating at all times, and that can be a bit challenging," he said.
"On the other hand, looking up through dense canopy would be really, really hard if you're walking around on the ground just with a pair of binoculars."
The researchers flew the drones from the James Cook University crane in the Daintree Rainforest Observatory. (Supplied: Emmeline Norris, James Cook University)
Ms Norris said that while she has enjoyed using a new tool, the drones do have limitations.
At warmer parts of the day she said contrast between the marsupials and trees became less clear, and there can be some instances of mistaken identity.
"Because green ant nests are made up of leaves, and when the leaves die and start to decompose they get really hot in the sunlight, from a distance it kind of looks like a large mammal in a tree,"
she said.
The cameras also struggle to detect the animals if there are any leaves in the way, but said she still sees a lot of potential for the method.
The cost is also prohibitive, with some thermal cameras costing between $10,000 and $30,000.
Bennett's tree kangaroos are one of two species of tree kangaroo native to Australia. (Supplied: Emmeline Norris, James Cook University)
Flying forward
Ms Norris said she hoped this was just the first example of observations on tree kangaroos using thermal drones.
"I think a lot of people have been put off from using thermal drones in tropical forest environments because they hear that they don't work so well in the warm conditions, or because the vegetation is quite dense," she said.
"This is still the very early stages of this research, and we're hoping to get some more opportunities to fly in different areas throughout the Daintree National Park so that we can learn some more."
The researchers say until now it wasn't known what Bennett's tree kangaroos typically eat. (Supplied: Emmeline Norris, James Cook University)
She said, along with the thermal camera, the high-resolution colour camera also introduced the potential to uncover more individual behaviours.
"We're able to zoom up and get those really nice close-up images so that we can hopefully identify individuals based on their markings," she said.
"Males often have scars and things like that, and we see what they're eating."