Father and son

Actually very interesting the way the son was trying to annoy his father, and the bull firmly but gently would push him out of the way with either his trunk or foot! Teaching him discipline.

Has he been split from his mother (and the rest of the herd) permanently to live with his father, or was this just a temporary mix?

I am pretty sure that Melbourne Zoo allows the calves (and the females) to go in with the male Bong Su for visits (as Taronga does).

The two boys were together again today, fully separated from the female herd.

Why not keep the calf staying with the female herd?

Its good for young males to sometimes associate with an adult bull. Helps them (and possibly assists hormonally too) to learn how to become proper males themselves. Is good enrichment for the adult bull also to mingle with younger males, as well as females. It also allows the younger males the chance to initially experience leaving their mothers on a temporary basis, where they may later need to leave them more permanently. This seems like good management to me.

This is an interesting photo to see, and this bull certainly has a more socially-enriched life than he used to when he was one of only two elephants at the zoo.