I agree with you regarding, as I said, species with high conservation value, but I don't think hippo bred in Australia are ever going to be returned to Africa

In fact, at this stage Bongo and Pygmy Hippo, Rothschild Giraffe are probably the only species which would stand to benefit and in turn contribute at a real conservation level from a greater level of participation between our region and that of other parts of the world.
Given our countries rather paranoid stance on importing antelope etc, I think if ZAA can open the doors for future imports they should try and get as many animals in as quickly as possible, for species we have here with a high conservation or display value, in case the regulators change their minds.
In the meantime, like I said, I am a lot less concerned about hippo, than say Bongo. Hippo obviously have such a long generation span; Dubbo has bred just 5 in the last 26 years, and Werribee 3 in what, ten years? I guess that's why, whilst the situation isn't ideal, our hippo population has not collapsed as rapidly as say peccary or any other species we haven't been able to import.
They've (the program coordinators) done well to get Bongo to persist for so long on a founding base of just 3 animals, though that could change soon.
I guess, as you mentioned giraffes, they are a sign of what can be done in the region to turn things around. Just ten years ago they had a highly unacceptable inbreeding coefficient, now it is vastly improved with the import of just a handful of animals from NZ and Europe (1).
So fingers crossed the same could be achieved with hippo.