Taphonomy of tortoises deposited by birds and Bushmen

In the semi-arid Karoo of South Africa's central plateau, tortoises are commonly preyed upon by raptors, some of which roost on ledges in the backs of small rock shelters. In the past, any suitable ledge could be occupied only when the shelter was not in use by Bushman hunter-gatherers. Thus, both agents could have contributed tortoise elements to the faunal deposits which accumulated int he shelter fills over the past two millennia. Element survival and breakage rates of tortoise remains in a recent shelter roost accumulation show reversed frequencies to those for tortoise carcasses left a raptor kill sites: what is abundant at the roost (skeletal elements, particularly from the neck and head) are scarce at the kills. When the roost sample is compared with the Bushman foodwaste sample beneath it, the two are readily distinguished by their element composition and condition. A surface sample from a neighbouring shelter without roosting ledges is also rich in skeletals, but lacks the characteristic cranials and vertebrae. Small carnivores are the suspected non-human agents. Although radiocarbon dates indicate an earlier hiatus in this sequence, no such raptor-like tortoise assemblages are detectable at this level.