The echidna is a monotreme like the platypus. They can be found in some zoos but, with them being very nocturnal, it can be very hard to get good photos of them. I lucked out that on this one day, there were two of them just wandering around as if they didn’t know it was daytime.
Now I just need to photograph three more species of echidna and a platypus and I’ll have collected the whole set.