The only big cats around at the time of Australopithecus (4-5 million years
- 2.5 mln years ago) were various Smilodon, (the sabertooth) but he only
lived in north and south america, and the most dangerous type (fatalis - the
one always shown), didn't show up until 2.5 mln years ago).
And species of Acinonyx, cheetah-like cats, who could have formed some
danger for the Lucy's kind (nothing like modern Lions or Tigers), but
remember please John, Smilodon an his kind also had brain volumes much lower
than todays tigers, lions and cheetahs, compared to these, they were what
lucy is compared to modern man - stupid !
All species evolve, homonids have, but so have their prey and their
predators. Putting a prehistoric homonid up against predators who you give
the qualities of their modern equivalents, is more than a little unfair.
Lions didn't develop until 2.5 mln years ago, and therefore came around the
same time as homo erectus.
I didn't find out the speed and body weigth of some of the Acinonyx, or
wether they hunted alone or in packs. I assume they will have preyed on the
occasional Australopithecus, but i don't think they can be compared to
modern big cats.
J. de Lyser