I fully agree with this. To use Bongo as an example - most zoos in the region holding this species (even the open range zoos) have had a pair or a trio. This is a species that can live in herds of up to 50 females and their young. Aside from the visual impact a herd of this size would have; importing larger founder bases would offset the consequences of some females not successfully breeding etc.
I am not sure that a tropical rainforest species that is quite often solitary like bongo really do congegrate in herds of up to 50 individuals. You might have the bongo confused with another Tragelaphus species?
I would underline that at the moment the bongo in Australia is far from being maintained in pairs or 3-somes. At best, there is one functional pairing and a few singletons+ in few other collections. I really cannot understand why import regulations remain a hold up to create some sound regional management with sufficient founder stock here. (SE Asia, Korea and Japan even hold bongo in numbers).
Following the thread, I do agree that any open range zoo in Australia - not just Monarto - would benefit from having 6 antelope species on the range: wildebeest, hartebeest, sable/roan antelope, gazelle big and small, impala and eland and/or kudu. Add on giraffe, rhino, elephant and warthog and zebra (plains and Grevy's) you would have a very nice set up.
When I look at the wildlife trading business pretty much the 6 named species can be imported in numbers. South Africa at the moment having the bulk of the business in selling surplus stock all the time and most species mentioned are freely available. But I could think of other countries like Namibia, Zimbabwe, even East Africa like Tanzania, Uganda and perhaps Kenya warming to an ex situ initiative if the net result is cash for conservation.
The bottom line: there are import restrictions in place and a system (obviously not working) to regulate vetted imports of exotic wild animals (and I assume this pertains to wild plants too) in the region. For the love of our brains, to me it remains absolutely incomprehensible a few informed zoo staffers cannot explain to bureaucracy the evidence-based need for population management with conservation value within Australia with regard to exotic wildlife.
It really should not take 10-15 years to accomplish an import before something positive "happens", nor the push back that seems to have occurred for yonkers years (the subject has been discussed time and time again for Australia/New Zealand). I assume there is a lack of political will coupled with a lobby by private interest groups to prevent these imports / exports (!!!) from becoming reality.
BTW: The import of the nyala sometime ago was the only high point to date.