Fit Travel: Top 10 Adventure Trips For a Good Cause

More than 90 percent of Madagascar's wildlife is found nowhere else on earth, including the elusive fossa, a carnivorous cat-like creature populating the African country's forests. Your mission—should you choose to accept it—is to help researchers learn more about their habitat and behavior by setting up traps; relaying info over high-tech radio-tracking transmitters; and measuring trapped and sedated fossa for study. You'll get in some great workouts, too—as well as take in some unbelievable scenery—while trekking up to 15 miles a day through rural villages.

You Need: Two weeks. ($2675; govoluntouring.com)