Black-backed jackals do hunt Cape fur seals.
They probably got started doing this when the seals would leave behind large amounts of afterbirth during their pupping season.
It’s just a short step from eating the culls and then moving onto hunting the pups themselves.
Because this is southern Africa, these are the “Cape” subspecies of the black-backed jackal. It’s the only jackal found in southern Africa. The one with the faded markings is probably just a color variant.
I don’t know this species well enough, but maybe they are like black wolves in that they fade a bit as they age.
Seals don’t eat the afterbirth?
According to the University of Google, they do not. Learn something new every day.