"猎取人头的蛮人" can be translated into English as "head-hunting savages" or "headhunters (in a derogatory or historical context implying savagery)".
"Head-hunting savages" directly conveys the idea of people who hunt and collect human heads, with the added connotation of being "savages" (uncivilized or barbaric).
"Headhunters" in a more general or historical/derogatory sense can also refer to those who engage in head-hunting practices, though in modern usage, it often refers to recruiters or those who seek out talent for jobs. Here, the context would clarify its meaning as the former.
For a more precise and contextually appropriate translation, especially if emphasizing the barbaric aspect, "head-hunting savages" would be a suitable choice.