Frogs click from rivulets around boulders, wind whips through the snow gums, and scarlet robins and buff-rumped thornbills abound in icy flurries.
The highest peak in Australia — Mount Kosciusko — is obscured by grey mist. Around it, smooth-looking, windswept ranges stretch as far as the eye can see.
But lurking within Kosciuszko National Park is a weed with the potential to do serious damage to this stunning environment.
Hawkweed is a daisy with flowers the colour of fire, and it could seriously damage the agricultural landscape stretching below the range.
The plant, which was brought from Europe as a decorative flower, takes over areas of ground so completely that nothing else can grow.
Hawkweed has devastated about 6 million hectares of land in New Zealand, where farms have been abandoned because livestock don't like to eat it.
Moreover, Kosciuszko National Park is home to vulnerable and endangered fauna like the broad-toothed rat, corroboree frog and pygmy possum — and the fear is that hawkweed will outcompete the native plum pine, and other habitats these animals rely on.
Luckily, there are the two spaniels standing in its way — and they're doing it all for the love of the tennis ball.
Spaniels bred for smarts, not style
Dogs are not allowed in National Parks, but an exception has been made for Sally and Connor.
The spaniels each have special permits — and little working jackets too.
"Sally is a cocker spaniel and Connor is an English springer spaniel," animal trainer Ryan Tait says.
"They are from working stock. They're not bred for their looks, they're bred for their ability to run all day and to sniff all day as well.
"There's only a handful of working-line spaniel breeders in Australia and … to be perfectly honest, they don't make good house pets, unless they have a job to do.
"Sally comes from a line of working cocker spaniels … a lot of them have been trained to find things like termites and other pest species, which means they're really good at doing intricate, small, short pattern sort of sniffing.
"Connor … his father is one of only two cane toad detector dogs in Australia and he also finds foxes and cats as well. His mum is also a field working dog, so we know he comes from a fit stock of dogs that have a high drive to search."
Mr Tait explains these kind of working dogs generally get trained from about eight weeks of age.
"We start doing things like creating a really strong desire to search for things, even if it's just hiding their food, or hiding their favourites toys, and trying to build up a high ball drive or play drive," he says.
And according to Mr Tait, training weed-detector dogs can be more arduous than training dogs to sniff out narcotics.
"There's probably more rules around this … to be honest," he says.
"That's something that's done so frequently … you can easily acquire pseudo narcotics to train the dogs on."
Hawkweed, however, is strictly controlled, as it now poses such a risk.
As she trains, Sally zooms past — zig-zagging madly with her nose to the ground.
She and her trainer, Ms Cherry, are each wearing a GPS device, so the ground they have covered can be mapped. And for every kilometre Ms Cherry walks, Sally runs about 5km, zigging and zagging backwards and forwards.
But the team behind the hawkweed detection program isn't just relying only the noses of dogs — they also are sending in the drones.
Eying hawkweed from the sky
In conjunction with the University of Sydney's Australian Centre for Field Robotics, and the Department of Environmental Sciences based at Macquarie University, they're working on using drone footage combined with a custom-made algorithm, to pick the weed's orange flowers out from the surrounding vegetation.
"If we send a drone out to do a survey, they can do 25 hectares in a day as opposed to us doing one," Ms Caldwell says.
"The only downside with the drones is the flower has to be present."
The team is also using drones for multi-spectral or hyper-spectral imagery to detect plants without flowers that aren't so easily seen.
"Rather than photograph, they actually [take] an image, so it's like a reflectance image and plants can reflect in different spectra," Ms Cherry says.
These two techniques — dogs and drones — are used in conjunction with a more traditional human sweep of the area, where volunteers cover quadrants of the terrain.
Where hawkweed species are identified, a program of cyclical herbicide application is implemented and the area is monitored, with strict biosecurity and quarantine regulations in place.
The National Hawkweed Working Group have also been experimenting with other methods, such as controlled burning and trying to harness aspects of the plant's natural biology, which are then used against it — like preventing the setting of seeds.
Still hope in the hills
Australia has a pretty sparse record when it comes to weed eradication, Ms Cherry says, but her team is optimistic.
"It would be the first weed eradication that we have documented from NSW," she says.
"We've got a few examples — one notable one from Western Australia where they eradicated an agricultural weed. [But] there's not many others."
It could take 15 years or more to eliminate hawkweed from the NSW highlands, because of the incredibly difficult terrain and the wiliness of the weed, but the eradication team remain positive.
"If you'd asked me in 2010-11 whether we could do it, I might've said no — but with new techniques and tools, I think we can," Ms Caldwell says.
If you see these plants contact your council weeds officer, the NSW Invasive Plants and Animals Enquiry Line on 1800 680 244, or email firstname.lastname@example.org