thank you. reporter: knowlton hosts hunting shows on the outdoors channels and organizes high-end hunts around the world. he describes himself as a passionate conservationist and argues old black rhinos that don t reproduce actually threat ton kill other younger rhinos. they re actually the biggest killers of rhinos in the area, and so throughout they put this group of experts together. they went out there. they identified them as a problem, and they need to be, for lack of a better term, exterminated for the species to continue. reporter: but knowlton faces scathing criticism from other animal rights groups. critics say the sanctioned hunts will only drive up the price for endangered ang malls. the message, americans will throw money to kill one of the last species. saying it s rarity of this animal meaning it s more valuable dead than alive. that s not going to help the rhino in the long-term.