As foothills and savannahs give way to lush jungle in Colombia’s Guaviare department, towering outcrops of some of the oldest rock formations on Earth rise as sentinels watching over crystal-clear streams and hidden caves decorated with ancient rock art. Walking along meandering trails in the dense rainforest of this fascinating region, every rustle of leaves sharpens the senses. In the stillness, you may feel a subtle awareness of being observed by something powerful. "Even if we cannot see it, we may hear it roar or see its tracks." -&nbs...