The Southern Viscacha, a high-altitude rodent of the Andes, appears "sad" due to droopy eyelids and a downturned mouth, but scientists said it's survival adaptation. Thriving at 2,500-5,000 meters, it withstands extreme cold, scarce water, and strong winds. Its thick fur, water-saving kidneys, strong legs, and social colonies are all evolution's tools for survival.