Osteophagia means "bone eating", apparently a fairly common habit of giraffes, although I have only seen it in the Pilanesberg.
Animals can’t always get all of the nutrients they require from their staple food sources and a perfect example is the giraffe, who supplements a herbivorous diet by chewing on another animal’s bone. Long after an animal has had its flesh fall (or torn) from its bones, those bones still contain a lot of nutrients, predominantly phosphorous and calcium, which remains a potential food resource. Of course, a giraffe is a strict herbivore and its digestive system reflects this; being unable to adequately process animal tissues, bones included, and so they merely chew on bones in order to glean some particles of the nutrients they need.
(an adaptation to the heat perhaps 
