It's reported they don't have natural predators but dogs and wild cats take juveniles.
However I was working in the bush a few years ago and discovered a freshly skun echidna on a log.
The skin, prickles down, was cleaned of all flesh and nothing else remained.
On the ground were some fluffy white feathers so obviously a raptor had managed to catch it.
It was ironic as the fresh skin was swarming with tiny ants come to clean up. Ants are the Echidnas favoured food
I've a photo but not very pretty sight.
Their claws are formidable and they are amazing diggers.
When approached they either run, at their slow 2.5kmph or stay and dig themselves down into the dirt. Latter is remarkably quick.
Then all you see is their spiky back protruding.
I wouldn't like to get tangled in them.
Here's about the best write up I've seen
The short-beaked echidna, a cute, waddling, well-camouflaged creature is this most widespread native animal in Australia. There are five sub-species of short-beaked echidnas. The Tasmanian short-beaked echidna is a subspecies of the short-beaked echidna, which is endemic to Tasmania.
www.bonorong.com.au