Tool use in primate species has extensively been reported in the literature but only rarely the more complex behaviour of advanced tool manufacturing has been reported in Old World monkeys. Advanced tool manufacture is defined not as simply detaching the tool from its substrate, but giving a new shape to it for its subsequent use.
When tools are modified, rather than just used, we are prompted to infer about the complex handling and cognitive abilities possesed by the observed subjects. Outside the purpose of feeding, tool use is comparatively rare. Presumably this is likely to be true more so for tool manufacturing, which implies the possession of a high level of sensorimotor intelligence.
We do not known how the captive status of this mandrill might have affected his ability to acquire this skill. Yet, this observation indicates that the species is potentially able of tool modification, allowing Old World monkeys to be represented for the first time in the group of primates able of advanced tool manufacture behaviour in a context not related to feeding.
This finding has been published in Behavioural Processes and later got into the news: BBC, The Telegraph, Daily Mail, El Mundo, Folha, etc. (see a press review in PDF). And at the radio: BBC radio 4.