Not far off the pace were Ramey Smyth and Aaron Burmeister.
All four were on the trail out of Elim. Seavey, the son of 2004 champion Mitch Seavey, spent just six minutes at that checkpoint and dropped a dog, leaving him with nine.
Zirkle spent nearly two hours in Elim and dropped two dogs, leaving her with 10.
Mushers try to stay within striking distance of the leader at this point in the nearly 1,000-mile (1,600-kilomter) race from Anchorage to Nome. That's because mushers are required to rest their teams for eight hours in White Mountain before heading the 77 miles (124 kilometers) to the finish line.
The closer the top teams can stay to the leader going into White Mountain the better chance they have of winning.
Sixty-six mushers began the race March 4. The winner will receive $50,400 and a new truck. The total purse of $550,000 will be shared by the first 30 finishers.
This year's winner likely won't break defending champion John Baker's record-breaking time of 8 days, 18 hours and 46 minutes, race spokeswoman Erin McLarnon said. It appears the race leaders are moving about two hours slower this year.
McLarnon said she expects the race winner to cross the finish line sometime Tuesday.
Zirkle had been leading until Seavey — described by his father as "fiercely competitive" — made a move and erased her more than two-hour lead with what was a faster-moving team. But Zirkle's team gained on Seaveycoming to Elim.
Several teams scratched and one was withdrawn Sunday. They included four-time champion Jeff King who scratched after his dogs didn't want to go the last few miles into the checkpoint at Unalakleet and were brought in by snowmachine. McLarnon said it appeared King's team had a stomach ailment.
Race officials withdrew Jake Berkowitz in Unalakleet after he cut his hand while trying to separate two blocks of frozen fish to snack his dogs.
"It just sounded like the knife slipped," McLarnon.
Mitch Seavey met the same fate last year when he nearly sliced off a finger opening a bale of bedding straw for his dogs. He was in sixth place late Monday.