Looks like you may have photographed the beginnings of a mating rut. I pulled this description of echidna mating behaviour off teh web site of South Australia environment.
From mid-May to early September, male echidnas actively seek out females to mate.
They form a line known as an ‘echidna train’, with the female leading the ‘train’, followed by up to ten males. A smaller, younger male is often at the rear of the line.
The male suitors follow the female for long distances until the female is ready to mate.
She then lies relaxed and flat on her stomach and the males that formed the ‘train’ dig a circular trench around her. Eventually the largest male pushes the competing rivals out of this ‘mating rut’.
He then digs more dirt out from the spot where the female’s tail is resting, lies on his side and places his tail under hers, and they mate.