It was done on the basis of Thong Dee (1997) and Porntip (1992) each having sons - Luk Chai (2009) and Pathi Harn (2010). Taronga didn’t have the capacity to manage additional bulls beyond Gung (2000), so the decision was made to build a new barn at Taronga Western Plains Zoo and transfer these five there.
This left Taronga with three cows - Pak Boon (1992), Tang Mo (1999) and Tukta (2010-2018).
The original plan (which remained the same even after Tukta died) was for the founder cows to all be reunited at Taronga Western Plains Zoo. Construction of the new herd barn isn’t even on the horizon yet and so when Monarto Safari Park committed to take Burma (1982), Putra Mas (1989) and Permai (1989), it was decided Taronga would pursue this avenue in phasing out elephants. During that time, they welcomed Anjalee, who is now pregnant of course.
I have said all along however that not transferring Thong Dee to Monarto Safari Park was a missed opportunity. She has no ties or breeding application at Dubbo, but could have been an asset to Monarto.