Red Heeler, 13 years old
For the past decade, Sam has spent the better part of every summer rafting Idaho's Class IV Middle Fork of the Salmon River, the lead dog in a three-pooch pack that comes along on nearly all of the Middle Fork River Expeditions' 10-plus guided trips. On constant lookout for deer, he's memorized nearly every inch of the 100-mile wilderness stretch. He knows when camp for the night is around the next bend and which rapids are the most troubling. "Now he gets low in the raft before each rapid," says Scott Wilson, Sam's boat driver. Though Sam's swims are far rarer than they used to be, he still gets knocked into the drink. When he does, he paddles straight to shore, then sprints down the bank until Wilson can find a spot to pick him up. With so many newbie clients, Sam has an endless string of suckers to pet him, even if he barges into open tents at 6 a.m. He's memorized the menus, too, and knows exactly when to beg. "Day five," says Wilson, "prime-rib night."