The remaining 60 minutes was all Auckland at Eden Park on Saturday evening.
The defending champion dominated the opening quarter of the game to shoot out to a 24-0 lead.
The Stags battled back through their powerful scrum and were unlucky not to be rewarded with some points.
But Auckland weathered the barrage and scored 40 second-half points to win 64-7 and stay in touch with the top four.
The home team opened its account early when halfback Jonathan Ruru ran into a gap and passed to the unmarked Waimana Riedlinger-Kapa to run it in.
Winger Salesi Rayasi had helped set it up with a strong run down the touchline and Auckland had stolen the lineout.
Moments later midfielder TJ Faiane bumped off a tackler and winger Caleb Clarke scored.
The Stags, for the most part, have defended well this season. But those early defensive blunders were not a good sign.
Southland was missing key midfielder Ray Nu'u. He has been solid in the centre of the park and his absence was sorely felt.
Rayasi was dangerous every time he carried and he proved too big and too strong to stop from 10m out to put his side further ahead with a quarter of the game gone.
The match started to feel like a training run for Auckland and the bonus point try was secured shortly after.
Southland had barely seen any ball. When it finally got some time in possession it was able to put some serious pressure on with a series of scrums deep in Auckland territory.
Referee Tim Griffiths resisted issuing a yellow card, despite Auckland conceding penalty after penalty.
When Southland grew impatient and spun it wide, Jordan Trainor nabbed an intercept and the opportunity was lost.
Blindside flanker Dalton Papalii, who was making his return from injury, bagged two tries in the second spell as Auckland pulled further away.
Auckland halfback Ruru had an outstanding game and made several telling darting runs. Rayasi was ever threatening on the left flank, while fellow winger Clarke showed some wonderful skills.
For Southland, centre Isaac Te Tamaki kept working hard and hooker Greg Pleasants-Tate had some good moments including getting over for a try in the 67th minute.