Even though the exhibit is large, I think they’re overestimating the capacity of the exhibit to function as a wild ecosystem given this is a species which can travel up to 80km in a day.
The bulls transitioning out of the natal herd will still be drawn to the natal herd beyond the stage when the adult cows are driving them away and then there’s contraception of cows to consider - Kulab who’s capable of conceiving, but who is unable to handle the birth process; cows they want to extend the birth interval by a year or two; and juvenile females of four or five years, who will begin cycling around this time. There’s also the potential for injury to young calves caught up in clashes from boisterous adolescent bulls.
As seen from the map, Werribee has the capacity to manage elephants across multiple paddocks. I have no doubt a fission-fusion transition as has been so successfully implemented at Dubbo is the way to go.
The keeper seemed pretty confident and excited about that as apparently it would be a world first. Whether it works or not will be to be seen, and they have the facilities to accomodate it if it dosen't.
Eventually the region will need a designated bachelor facility; as obviously Werribee won’t be serving as one (besides holding a few). Monarto seems the best option going forward. Sydney could potentially be another facility (but can only hold up to a pair of bulls).