Armando, Frank, Matthew, Simone, thanks.
Simone, the shots were made on a D800 with 80-400VRII. I found that a very good wildlife combination, despite not being the D800's speciality. The lens is a great safari lens, being easy to handhold and not too heavy for walking around.
I do not think the X-T1 could have captured these shots (there are more in the series, all spot on focus) because of the slow AF lock on, the small number of PDAF points, and the viewfinder lag. Maybe the X-T2 will solve these issues. On the other hand, the Fuji 100-400 is optically superb (even better than the Nikon 80-400), even with the 1.4 t/c installed, and the AF is probably fast enough if the camera supporting it is fast enough.