Rare images captured of sand goannas locked in a violent scuffle over a female.
The adult goannas (also known as Gould's monitors or sand monitors) were spotted through the office window of an environmental consultancy just south of Alice Springs.
Photographer Chris Watson was working there at the time and raced outside with his camera.
"I was lucky enough to have the window desk...goannas used to go about their day to day business right in front of us really, but this was the first time I'd seen this," he said.
"These two males locked horns and were fighting over the local female monitor who'd dug her burrow there.
"They were fighting for about ten minutes, wrestling and throwing each other around."