Trim Stab, what reason do you have to believe that this bunch of Boko's are cannibals?
Cannibalism is not uncommon in Nigeria - try googling it and you will find plenty of ghoulish recent references. These are just the stories that have sufficient corroboration to make it through the veracity filters of western press outlets. I read the Nigerian newspapers (when I am out there) and there are plenty of other locally reported stories that never make it into the western press. These are just the stories from reasonably literate areas of Nigeria too.
The villages in the north and east are totally cut-off from central government, the police (even if they dare go there) are utterly corrupt and unreliable. Nigerians eat anything they can kill. I think it is a safe-bet that any young child who dies of malaria or snake-bite will end up in the soup pot.