South Africa have consolidated to move to 5-144 but Australia remain firmly on top at tea on day one of the Boxing Day Test at the MCG.
Wicketkeeper Kyle Verreynne (40 not out) and bowling allrounder Marco Jansen (38 no) are inching the Proteas towards a more respectable total after they collapsed to 4-58 by lunch.
No.5 Khaya Zondo (five) lost his wicket early in the second session, falling when Marnus Labuschagne took a stunning catch off Mitchell Starc's bowling.
But Verreynne and Jansen were able to steady the visitors with an unbeaten 77-run partnership.
Labuschagne put down a tough chance off Jansen at short-leg, before the giant Proteas No.7 then smashed Nathan Lyon for back-to-back boundaries.
Jansen received another life in the last over of the session, with Usman Khawaja dropping a catch in the deep off Starc (2-39).
Earlier, Australia had South Africa's brittle batting line-up under immense pressure after rolling them inside two days on a green Gabba pitch in the first Test last week.
South Africa made an encouraging start at the MCG after being beaten in record time in Brisbane, but they lost three wickets, including captain Dean Elgar, in the last half-an-hour of the first session.
After crawling to 1-56, the Proteas lost 3-2 to vindicate Australia captain Pat Cummins' decision to bowl first for the second consecutive match after winning the toss.
Prolific quick Scott Boland (1-23) claimed the opening wicket of the second Test, removing opener Sarel Erwee (18) as Khawaja hung on to a catch at second slip.
The 33-year-old Victorian whipped his home crowd into a frenzy after he retained his spot in the Australia XI following fellow paceman Josh Hazlewood's decision to rule himself out of the match as he continues his recovery from a side-strain injury.
This match marks Boland's return to the scene of his famous Test debut last December, when he ran through England with 6-7 to secure man-of-the-match honours and help Australia retain the Ashes.
No.3 Theunis de Bruyn, who was promoted into the Proteas team for this match, was out to allrounder Cameron Green (1-19) after badly mistiming a pull shot to be caught by wicketkeeper Alex Carey for 12.
Elgar endured nervous moments after playing onto his stumps from a Boland delivery as the ball rolled so slowly that the bails did not dislodge.
The left-handed opener, who passed 5000 Test runs during the session, was shortly after dropped when Lyon put down a tough chance off Green's bowling.
But Elgar failed to capitalise on his good fortune and was run-out for 26 by some brilliance in the field from Labsuchagne.
© AAP 2022