Earth’s most fascinating creatures often hide in the most remote places. While many species roam across continents, some animals have evolved in such isolation that they exist nowhere else but a single mountain, island, or forest. These biological treasures tell stories of evolution’s creative power when geography separates populations for thousands, sometimes millions, of years. These 37 animals showcase nature’s tendency toward specialization and remind us how fragile these one-of-a-kind creatures truly are.