Maybe "bribe" was too strong a word, and if so, I apologize. And I never meant to suggest anything "shady" was happening. What I'm referring to is that sometimes American zoos (and maybe others) have "encouraged" other nations to release their high-profile animals by making a major contribution to that nation's conservation efforts. It's all for a great cause, but certainly there is a clear "quid pro quo" thing happening. I think I first heard the word "bribe" from a zoo-insider (who works in a particular US zoo) friend of mine.
The most obvious example of this has been with China and their giant pandas. Almost everyone in the zoo world knows that San Diego, Memphis, and Atlanta (not sure about National) have had to pay "conservation contributions" of $1 million per year for the benefit of displaying their pandas. That "fee" has recently gone down to about half that price, which will likely allow Atlanta and Memphis to continue their panda exhibits. I honestly don't know if zoos have the same kind of relationship with the Australian government, but I do know that your government is very restrictive in releasing your high-profile animals (koalas, platypuses, etc.). I have heard that Albuquerque's Rio Grande Zoo is working with the Aussie authorities to release a bunch of Tasmanian devils soon, but that's a different story (to save the species from cancer-induced extinction).
Again, I apologize if the "bribe" word was offensive.