Naturalist Vitaly Nikolaenko worked in close proximity to brown bears for 30 years -- until one viciously killed him. Could it have been a shortage of food or did Vitaly?s own actions spark the attack? NGC sheds light on what actually happened.

Russia's Far East is famous for its long and brutal winters, and the undisputed king of this frozen domain is the Siberian Tiger. Hunted almost to extinction, there are now only 500 of these elusive cats left in the wild , and they are spread out across almost 70,000 miles of wilderness . Incredibly stealthy with a killer camouflage, these tigers are rarely seen. But when a researcher is suddenly attacked in the vast frozen forest, Investigators are left scratching their heads. As the researcher battles for his life, our investigators analyze a rash of similar attacks in the area. What they discover only adds to the mystery. What is causing these normally elusive cats to come out of hiding and attack humans? And is the real predator the tiger or the man?

In West Africa's Sierra Leone, a chimp charges a touring car, breaks a window and bites one of the passengers. What provoked such violent aggression?