Answer:
Platypuses have few predators in the wild, because they mainly hunt underwater and live in hidden shelters, from tropical north regions to the sub-alpine areas of southern Australia.
The introduction of red foxes as a predator for rabbits may have had some impact on platypus numbers on the mainland. Feral cats are another platypus predator, but the platypus's principal enemies are humans. Humans used to hunt them for their fur, but they are now protected. The danger is now not from hunting, but from destruction of their environment. Also, the use of fishing nets in freshwater creeks and rivers resulted in large numbers being drowned, but this practice has been banned. So, technically, man is not the platypus's predator because he does not eat it, but he is a threat to the platypus. The platypuses were and are affected by man but not eaten by him.
Natural predators of the platypus include snakes, water rats, goannas, spotted quolls, eels, hawks, owls and eagles. In the north of its range, dingoes are another predator. Lower platypus numbers in far northern Australia are possibly due to predation by crocodiles. On occasion, large freshwater eels (which may be twice the length of a platypus) have been thought to take platypuses.