Many herbivorous (plant eating) animals face the problem that their diet does not provide sufficient minerals to meet their needs. Many reserves provide mineral salt-licks (usually placed near hides, water holes and other protected viewing areas) to assist with supplementing these shortages. But it can also give rise to animal activities that, as observers, we consider odd or eccentric.
A number of animals indulge in geophagia (the act of eating soil for minerals) and/or osteophagia (gnawing bones for calcium) as a dietary supplement. We caught this kudu cow, most definitely not a carnivorous species, happily gnawing away on a bone. She dropped it and picked it back up a number of times, to address her calcium deficiency. Perhaps in an effort to assist the development of a calf?