Bones of Ol Pejeta: Neotaphonomic and Ecological Survey (BONES)

1. Bones of Ol Pejeta: Neotaphonomic and Ecological Survey (BONES) Kris Kovarovic 1 & Briana Pobiner 2 1Department of Anthropology, University College London, United Kingdom, 2Human Origins Program, National Museum of Natural History, Smithsonian Institution, USA Smithsonian This long-term project will address two major issues in human evolution in concert: 1) reconstruction of the environmental context of hominin evolution in Africa through the study of faunal remains and 2) the potential niche of hominins within the carnivoran paleoguild through documentation of carnivore habitat preferences and predator-prey relationships. Both research questions – the habitats and mammal communities in and with which hominins were living, and how hominins were interacting with carnivores to acquire prey resources - require approaches that are based on comparative analyses of living mammal communities. We will investigate both past and present ecologies in a long-term study of the bones of modern mammals that accumulate on the ground in a mosaic of different habitat types in Ol Pejeta Conservancy (OPC) in the Laikipia District of Kenya. These “bone communities” will be used to: 1. generate models for reconstructing ecological conditions in the past, with a focus on predator-prey dynamics and mammalian habitat preferences and affiliations 2. pinpoint areas of difference between the bone communities we find on the ground in the modern landscape and the living mammal community that we observe today, and generate and test hypotheses to explain these differences • BONES: A Study of Mammalian Communities • We hypothesize that a long-term survey of bone communities at OPC will track changes in the living mammal communities including: • Changes in ungulate habitat preferences, using correlation and multivariate analyses between abundances of bony remains of ungulate species or “ecomorphs” and habitat variables (Andrews et al. 1979; Kovarovic and Andrews 2007; Miller and Behrensmeyer 2005) • Changes in relative predation level on specific ungulates, using frequency data of predator-specific kill remains of different prey ages and sexes (Pobiner 2005; Pobiner and Blumenschine 2002); and in specific habitats, using frequency data of predator-specific kills of remains in each habitat • Changes in species composition of animals preyed on by different predators indicating changes in prey preferences, also using frequency data of predator-specific kills • Changes in overall carnivore competition and predation pressure, using differential bone survival and limb skeletal element and portion relative abundance data (Blumenschine 1989; Faith and Behrensmeyer 2006) • Changes in predation pressure in particular habitats based on ecomorphological characteristics of prey species remains (Kovarovic and Andrews 2007) • Changes in overall prey biomass and prey species abundances, using bone and species frequency encounter data • BONES: The Longitudinal Study • Over several years we will record information collected on all visible mammalian skeletal remains encountered on pre-determined 1 km transects in all of the OPC habitat types. Data collected will include: • species-specific data (mammal taxa present, predator identity for kills) • Predator identity will be based on previously established taphonomic data collection (Pobiner 2005), including prey size- and skeletal part-specific bone damage and destruction profiles, tooth mark size and distribution. • taphonomic data (skeletal elements present, weathering stage, indices of carnivore damage such as long bone epiphysis : shaft ratio and relationship to bone density) • ecomorphological data (measurements of adaptive skeletal morphologies that relate to the exploitation of particular habitats). • Previously developed ecomorphological models, which predict the habitat affiliation of mammals on the basis of adaptive skeletal morphologies that are known to relate to habitat exploitation, will be applied to all encountered ungulate remains (Kovarovic and Andrews 2007). We will analyze the ungulate bones encountered on the transects in this way in order to determine if the bones of these “ecomorphs” are accumulating in their preferred habitats and if carnivores continue to sample preferred species from these habitats, even after changes in the mammalian community occur due to the removal of the fence. • From these data we can create models for interpreting fossil mammal ecologies. These data will be compared across the habitat types in OPC and, eventually, over a period of several years. Ol Pejeta Conservancy: A Unique Opportunity • 1989: Sweetwaters Game Reserve (SGR) opened as a sanctuary for the endangered black rhino, ca. 97 km2 • 1999: Earthwatch project (Kenya’s Black Rhinos) initiated to study the behavior, ecology, demographics of mammals and vegetation associations • 2004: SGR purchased by Fauna & Flora International • 2007: removal of a fence that previously enclosed SGR within the larger Ol Pejeta Ranch created Ol Pejeta Conservancy, or OPC (>360 km2). See Fig. 2. • This recent fence removal has stimulated shifts in mammalian behavior and habitat affiliations, creating a unique opportunity for us to study the taphonomy of ecological processes as they occur and stabilize over time in a natural landscape. . Figure 1. Map of Kenya, showing the approximate location of OPC. An accurate assessment of hominin palaeoenvironments based on analyses of fossil fauna requires an awareness of modern mammal behaviour - including their relationships to one another and to their habitats. BONES will allow us to investigate how landscape-scale taphonomy and carnivore predation affect ecomorphology-based reconstructions of past environments. In particular we will be determine if there are biases in the representation of certain habitat types or in habitats dominated by particular predator or ungulate prey species. Figure 4. The ecological relationships of carnivores and ungulates can be understood through the analysis of the visible bone communities (see above) Figure 2. Vegetation map of Ol Pejeta Conservancy, also showing the delineation of the former Sweetwaters Reserve and the adjacent Ol Pejeta Ranch, now comprising OPC. References Andrews, P., Lord, J.M., Nesbit Evans, E.M., 1979. Patterns of ecological diversity in fossil and modern mammalian faunas. Biological Journal of the Linnaean Society 11, 177-205. Blumenschine, R.J., 1989. A landscape taphonomic model of the scale of prehistoric scavenging opportunities. Journal of Human Evolution 18, 345-371. Faith, J.T., Behrensmeyer, A.K., 2006. Changing patterns of carnivore modification in a landscape bone assemblage, Amboseli Park, Kenya. Journal of Archaeological Science 33, 1718-1733. Kovarovic, K., Andrews, P., 2007. Bovid postcranial ecomorphological survey of the Laetoli paleoenvironment. Journal of Human Evolution 52, 663-680. Miller, J.H.,Behrensmeyer, A.K., 2005. Skeletal distributions across time: A multivariate approach to the changing taphonomy of Amboseli Park, Kenya. Journal of Vertebrate Paleontology 25, 92A. Pobiner, B.L., Blumenschine, R.J., 2002. Patterns of bone damage and destruction by larger African felids and hyenids: implications for zooarchaeological analyses. Nyame Akume 57, 68-69. Pobiner, B.L., 2005. African carnivoran taxon-specific bone modification patterns: experimental evidence. Journal of Vertebrate Paleontology 25, 100A. Figure 3. SGR mammal census data from 1996–2003. Census data over the next few years, collected in different areas of the conservancy by Earthwatch, will indicate which species are migrating into new habitats after the fence removal. Acknowledgements We thank the Kenyan government and OPC management for permission to conduct research at the conservancy. We are also grateful for the involvement of our collaborators: Dr. Geoffrey Wahungu (Wildlife Management, Moi University, Kenya), Nathan Gichohi (OPC), Professor Peter Andrews (Natural History Museum, UK), Dr. Rhonda Quinn (Earth and Planetary Sciences, Rutgers University, NJ) and Dr. Nick Walton (Legendware, UK).