I came across some stuff on alleged japanese cannibalism during ww2 of captured allied soldiers. Some of the claims were that this stuff went on as early as 1942, so it wasn't entirely due to their supply lines being cut off and them starving. There is a book which apparently deals with this called Hidden Horrors.
There was a discussion on a forum about this, and I found the following interesting:

http://www.ww2incolor.com/forum/archive/index.php/t-3503.html

"I noticed reading Australian Daily Intelligence Reports at Battalion levels, that Australian Infantry also came across many unburied Japanese soldiers in close proximity to inhabited Japanese huts. Everywhere, near Gona, Buna, on Bougainville...
Conclusion was, that when Japanese wounded died, his "mates" just carried him a few metres away and tossed into jungle.

For people from European civilisation it is unbelievable... Proper honourable burial of fallen fellow soldiers is something absolutely fundamental.
My father was in North Africa where troops in action moved very quickly.
He told me that leaving unburied collegues was extremely rare. Even if such thing happened, they always tried to come back and find the place. Most often fallen Allies were properly buried by Germans or Italians with marked graves, crosses and secured dog tags.
It may seem unbelievable, but in Polish Carpathian Brigade were Jewish soldiers which did not deserted and opted to stay in the Polish Army.
One of them was killed together with a crew of Bren Gun Carrier near Gazala. Their mates could not bury them - they had to run away from ambush.
When they came back after Germans retreated, they found graves with crosses. One grave had just stick and David's star drawn on the piece of scrap steel attached to it.
So, Germans, nazis - (anyone can say) - went to trouble to dig a grave for a Jew in 40 degrees C heat.

Japanese soldiers did not bother to bury their own killed mates. They preferred to cut a fresh meat from them to prepare their evening bake."