Sadly, one of the news stories is probably more revealing than it wanted to be about why these animals are endangered:
Because we're bloody ignorant.
The Age claims (with emphasis added):
Threatened mammal species include the African mountain gorilla, the emperor penguin of Antarctica and the Sumatran orang-utan.
Not a mammal!
Penguins have beaks. Lay eggs. Even putting aside the platypus for a second, I think those feature would twig to most people that penguins are birds, not mammals.
Does nobody fact check anymore?