Just to clear a few things up about the feeding habits of the Jackal and the misinterpretation that they are inefficient hunters.
In my guiding experience I have seen Jackal conduct highly well planned attacks on warthog piglets with the mother present, just a few days ago I was on a game drive, and as the drive was coming to an end I bumped into a Jackal on the move, as he foraged through the grass he became highly curious with a tuft of grass. All of a sudden a snake moved out and the Jackal pursued it and started making very precise bites, nipping at the tail end of the snake knowing how dangerous the bite can be. This is just proof that even though it was all about chance he stumbled across the snake he was still highly specialized in making the kill, in avoiding the bite and eventually came off with a full belly and unharmed.
With the impala lambing season on full foot forward it would not surprise me if these little artists of attack take full advantage of their predatory ability to pick up weakness and once again make the kill.