New perspectives in vertebrate paleoecology from a recent bone assemblage

Abstract

Interpretations of vertebrate paleoecology depend on knowledge of taphonomical processes which alter the composition of the preserved fossil assemblage from that of the original community. Study of the potential fossil record of a recent mammal community in Amboseli National Park, Kenya, shows the effects of some of these biasing processes and demonstrates how a bone assemblage on a modern land surface can be a source of past and present ecological information. In the bone assemblage, species presence or absence and relative abundance differ from recorded living species occurrences and population sizes: only 74% of the extant species in the basin are identified in the bone sample, and carcass abundances vary significantly from known population sizes of the major herbivore species. Both biases appear to be strongly correlated to body size, and this results from greater destruction of bones of smaller animals within the weight range from about 1-1000 kg. This size-biasing against small species appears to be due primarily to the greater susceptibility of small bones to destruction by carnivore mastication, breakage through bioturbation (trampling), and physical and chemical processes of weathering. Size-biasing resulting from such primary processes can thus be inherited by buried bone assemblages whatever their final mode of deposition. The bone assemblage also provides information on the spatial distributions of the major herbivore species over six major habitats. Patterns of strong habitat specificity are accurately represented in the bone assemblage. However, the record for certain species is affected by their seasonal and diurnal habitat shifts so that their bone distributions do not match live census data. The Amboseli bone assemblage provides a modern analogue for taphonomical processes which may have affected fossil assemblages derived from paleo-land surfaces prior to fluvial transport. It also helps to define limits of resolution in interpreting paleoecological information from such fossil assemblages.