Mules often do the work of heavy machinery, for a fraction of the cost. But their future is in doubt as budgets tighten and new technology takes over.
Sometimes, the old ways of doing things are best.
I went to see the mules in action at their base in Mammoth Lakes in the Inyo National Forest on the edge of the Sierra Nevada Mountains.
Interviews with forest packers Michael Morse and Lee Roeser from the Mammoth Ranger District plus intern Katy Bartzokis and blacksmith (the mule shoe guy) Zack Campbell.
BBC WEBSITE: Can firefighting mules balance California's budget?