The fourth annual Primal Quest endurance race sends competitors across a grueling 600-plus kilometer course requiring trekking, mountaineering, horseback riding, canyoneering, mountain biking, whitewater swimming, paddling, and day and night navigation.  

With roughly 450 miles of harsh desert terrain, sweeping rivers and high alpine passes to traverse, using only a map and compass, many teams may not even reach the finish line.  Those who do finish are competing for a share of a total cash purse of $250,000 — the largest in the sport of adventure racing.

Yahoo! Adventure Beat is featuring daily updates of the 10-day event, with image galleries from many of today's top outdoor photographers. Interested? Add an alert for daily updates.

Primal Quest:The Desert at Dawn
Dispatch 1: Over the weekend Primal Quest subjected its athletes to days of gear check and skills certification.  Competitors were both anxious to start and apprehensive about the 10 days and nights of travel in store for them.  For stories from the gate, read the dispatch or visit the photo gallery.

Primal Quest: Water Connections
Dispatch 2: The endurance racers in Primal Quest battled the desert heat in the second leg of the race, and race organizers hurried to get more water onto the course to keep racers (both two- and four-footed) hydrated. For more hot news, read the dispatch or visit the photo gallery.  

Primal Quest:The Heated Race Continues
Dispatch 3: Primal Quest Utah has now entered its third day. In temperatures reaching 104 degrees, the lead teams have covered roughly 200 miles; the teams at the back of the field are more than 75 miles behind. For news from the course, read the dispatch or visit the photo gallery.

Primal Quest: Endurance meets exhaustion
Dispatch 4: The leaders have been racing with little or no sleep — leading to mental errors that could decide the race. Follow competitors down rivers and through slot canyons. For more on the story, read the dispatch or visit the photo gallery.

Primal Quest: Thrown for a loop
Dispatch 5: Five days into the competition, race management has found a way to make the challenge harder, even as the lead teams race without sleep and the squads in the back of the pack begin to show signs of wear. For course updates, read the dispatch or visit the photo gallery. 

Primal Quest: Race for the finish
Dispatch 6: While the remaining teams in the challenge near the finish, one-time leaders in the race have begun to stumble as the effects of sleeplessness provoke costly errors. For reports from the field, read the dispatch or visit the photo gallery.

Primal Quest: The race is won
Dispatch 7: Exhausted but ebullient, the odds-on favorite team staggers across the finish line to win the grueling race.  How would the winners describe the race? "Adventure torture," said one. Read the dispatch.

Primal Quest: Independence Day
Dispatch 8: The last of Primal Quest's exhausted racers crossed the finish line July 4, giving whole new meaning to the term "Independence Day" and officially ending nine long days of one of the toughest endurance challenges on the planet. Read the Dispatch.

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