PUNTILLA LAKE — On a spectacular night with the stars shining bright overhead and a waning gibbous moon ducking in and out of a band of clouds along the southern horizon, the complexion of a fabled Iditarod Trail fat-bike race changed from nice to naughty.

By morning a race that had been rocketing north at a record pace would be slowing to a walk.

The first problem came in the form of a moose, a rare visitor in recent times to the south-facing foothills of the Alaska Range where the snow piles deep enough to bury willow browse. This one entered the trail near Red Lake at some time during the day when temperatures were near 40 degrees.

From there, the animal began a march up the middle of the trail for 10 miles or more. Every track it left behind froze into a crater. Afterward came a couple inches of new snow, just enough to make a fat-bike tire slip a little side to side.

Together, between the fresh snow and the frozen “moose holes” — an Iditarod Trail headache about which the late and legendary dog musher Susan Butcher regularly cursed in her day — the trail became impossible to ride in some places and merely difficult in others.

“It was brutal,” said Iditarod Trail Invitational cyclist Clinton Hodges III, a rookie from Anchorage. “That was the toughest thing I’ve ever done.”

Invitational race leaders Tim Berntson from Anchorage and Tyson Flaharty from Fairbanks continued to push the pace anyway,  following the moose steadily toward and then down the dreaded “steps” that descend summer cliffs above the Happy River.

The duo managed to ride more than walk. Flaharty credited the just-do-it determination of the 42-year-old Berntson, a two-time Invitational runner-up. Berntson pointed to the youthful enthusiasm of the 30-year-old Flaharty.

The steps were the best part of the hugely moguled trail beyond the checkpoint at the Winterlake Lodge at Finger Lake. Precipitation that has fallen as rain in Anchorage and other parts of coastal Alaska has come as snow here — feet and feet of snow.

As a result, the Iditarod is more a ditch than a trail. The Happy steps were easy because there is no way to fall off the trail. The berms on either side prevent it. Unfortunately, moose that get in the ditch like the easy walking and don’t want to jump out into the deep, crusted snow on either side.

This moose seemed to find the Idita-ditch the perfect ramp down to the river.

One would have thought it might exit the trail in the valley of the Happy, but no, it marched right back up the gorge trail on the far side of that Skwentna River tributary. Berntson and Flaharty pushed.

The cyclists struggled. The moose didn’t seem to care.

A mile or so beyond the top of the gorge, the animal found some willow close to the trail and paused to browse. It’s tracks grew fresher, and Berntson and Flaharty found themselves in an area where the snowy trail looked to have been churned by a gang of moose. There they could not ride and pushed some more.

Eventually, the moose did abandon the trail, but by then the cyclists were high enough in the foothills that the winds that have whipped the pass above in recent days had rearranged the mountain snows.

Some of the trail was blown in. Some was half blow in. Some had just enough snow at the bottom of the big and many moguls left in the wake of the Iron Dog snowmachine race to make life miserable.

A tired Berntson said he would pedal down into the bottoms hoping to maintain enough momentum to get up the other side. If he was lucky, he made it. If he was unlucky, the bike stalled, and he had to push.

The result was recorded in the speeds of the two lead riders, who averaged almost 16 mph over the first hundred miles of trail. They averaged only about 5 mph on the 35 miles coming in here from Finger Lake.

A satellite tracking device on Berntson’s bike, which uses coordinates from the Global Positioning System (GPS) to calculate the speed at which people are moving over the ground, recorded a top speed of 6.6 mph on a downhill. The slowest speed? Point-zero-seven mph.

A race that had been clearly on record pace, no longer looked to be so as Bernston and Flaharty slept in a warm, wood-heating log cabin here and those behind them on the trail struggled north.

Outside more snow was starting to fall and Steve Perrin, owner of The Perrin’s Rainy Pass Lodge, reported the trail blown in  for much of the 15 miles of climbing to Rainy Pass.

“It looks like we’ll be pushing some more,” two-time Invitational champ Jay Petervary said when he pulled into the checkpoint. One of the early leaders in the race, Petervary had a bit of a problem in the night.

He left Winterlake wearing the lookalike boots of Dan Dittmer, a mechanical engineer from Minneapolis. Petervary’s boots are two Euro-sizes larger  than Dittmer’s, but as Petervary observed later, the extra insoles he puts in the bottoms of the boots for warmth make them feel much smaller.

So he didn’t notice when he pulled on Dittmer’s boots at the lodge and took off on the trail. His first clue was when the clips on the bottom of the boots wouldn’t fit his clip-in pedals. He blamed ice and kept going down the big hill that drops from the checkpoint to Red Lake, where he stopped to chip the ice out of the clips only to find out he was wearing boots with clips for the wrong pedals.

Meanwhile, Dittmer was back at the lodge trying to figure out who took his boots. He finally deduced it had to be Petervary, pulled on the boots left behind, and took of to chase down the Idaho cyclist. They met not far from the lodge, Petervary having pushed his bike back up the hill to get his boots.

Both men arrived here around noon Monday. Charly Tri, another Minnesotan and an early race leader, did not. He dropped out with a bad back at Winterlake. Back along the trail from the checkpoint racers were stretched out for almost 100 miles.

Well-known Willow runner David Johnston was leading those on foot. He was in Skwentna. Another runner, Klaus Schweinberger, was bringing up the rear of the event. He was in Yentna Station.