KALTAG -- The Yukon River can be dull for a dog.
No twists and turns. Just a flat, snowy desert interrupted by islands of spruce and willow trees. Scenery that can lull a musher to sleep after seven days on the Iditarod Trail.
"About five miles ago we had a collective 'Holy crumb, we're tired' moment," Iditarod leader Aliy Zirkle said Saturday, shortly after becoming the first racer to arrive at this riverside village checkpoint.
Her knees buckled with fatigue as she stood on the runners about five miles from the town, Zirkle said. The dogs nodded off even as they ran the frozen river.
"I fell asleep for a while. They feel asleep for a little while. You're not supposed to do that while you're mushing," the musher said.
Zirkle, who gained the lead by rocketing through checkpoints and resting along the trail instead, lingered nearly six hours before leaving for Unalakleet and the windy Norton Sound coast. She's bracing for a sleepless weekend.
On Zirkle's tail is a pack of former champions and young contenders eager to hunt her down. All believe Zirkle, who became the first woman to win the Yukon Quest in 2000, is catchable.
"The gap is closing," defending champion John Baker said in Kaltag. He unpacked his sled as other top teams -- 2004 champion Mitch Seavey, emerging heavyweight Aaron Burmeister of Nenana -- inspected paws and cracked frozen beef for their huskies.
"I say that because there's going to be teams that are coming in from Nulato and are going to be fresh and they're not going to be staying," Baker said.
The leaders rested in high spirits after a morning of clear, cold skies and long shadows along the Yukon.
Zirkle arrived with 14 dogs but dropped two, including a 2-year-old named Scooter who suffered a hematoma on a front leg, before she left.
Zirkle has stayed a step ahead of other distance-mushing heavyweights by skipping rest at checkpoints and camping along the trail. The schedule allowed Zirkle to shorten difficult runs leading to the Yukon River.
Her decision to blast through Ruby and rest hours down the trail was the best move of the Iditarod, Baker said Friday.
In Kaltag, Zirkle agreed.
Her plan, she explained, was to avoid wasting the energy the dogs built during a mandatory 24-hour rest in Takotna.
"That would have been too much to bring them all back up and perky and then bring them all down with a 13-hour run," she said. She decided to split the more than 200-mile trip to Galena into roughly 70-mile runs, using a GPS to gauge the distance.
It worked. Even as Zirkle sprinted through Ruby, other mushers who rested at the traditional checkpoints instead of camping, such as Seavey, complained of a long slog into the village.
Surprising your rivals can pay off in a race where mushers plan every moment days or even months in advance. In 2010, Lance Mackey captured his fourth win by skipping rest in Kaltag and forging ahead 85 miles to Unalakleet.
Zirkle said pushing through Kaltag this year wasn't an option. Not when she was dozing in the sled.
Seavey says the time for unconventional tactics has passed.
"It becomes a test of wills sometimes. You keep pounding it out and see who's still there," he said. "There's not a lot of tricks to be done yet. There's no more rest to cut."
Burmeister, a 36-year-old who is catching a cold even as his dog team seems to grow stronger by the mile, trained in Nome this season and sees at least two opportunities for bold moves before the finish line.
One risk the leaders can take is pushing a team on a 90-mile trek up the windy coast from Unalakleet to Koyuk, bypassing rest at the midpoint village of Shaktoolik. Ramey Smyth and Hans Gatt did it last year while trying to gain ground on Baker during his record-setting run.
"That's a pretty ballsy move," Burmeister said.
Another option is going nonstop from Koyuk to White Mountain. Ninety-four miles.
A seventh-place finisher in the 2009 Iditarod, Burmeister said he doesn't know if the other mushers chasing Zirkle could make such a run without exhausting their teams and hobbling to the finish.
But he could, he says.
"The way they're eating and drinking right now, we can do a lot still," he said.
Zirkle's team of tiny huskies -- among them, Scruggs, Nacho and Boondocks -- gobbled their food at the checkpoint too. The dogs come from a small kennel. Like kids with few classmates, they get more attention from the teacher.
"I think they're like people. If you respect them, they'll respect you," Zirkle said before leaving Kaltag.
All along the trail, Zirkle has said her team is physically capable of winning the Iditarod. It's up to her to make it happen behind the sled, she says. By the time she reaches Unalakleet sometime early Sunday, she'll have 221 miles to go.
"I don't feel like the Iditarod's mine. I just feel like I'm in the race right now," she said.