Differing impact of carnivores on bone assemblages in two East African Ecosystems Anna K. Behrensmeyer Department of Paleobiology, Smithsonian Institution Briana L. Pobiner Department of Anthropology, Rutgers University

Goals: Test the effects of different dominant carnivores on recent bone assemblages Impact on models of carcass and prey availability for early hominins Flesh slicerBone crusher

Amboseli Laikipia

wildebeeste Burchell's zebra Grant's gazelle Thomson's gazelle impala buffalo elephant giraffe hartebeest beisa oryx black rhino eland Frequency Laikipia Amboseli 1970's Laikipia and Amboseli: Live Census Data

LaikipiaAmboseli X XX Different Ecosystems Different Times What is the taphonomic impact of different top predators? 11 transects12 transects

Variables to Compare: Average number of bones per individual Skeletal part survival Completeness of femora and humeri Damage to femora and humeri Juveniles vs. adults

Burchell’s zebra only

Laikipia Ecosystem

Laikipia Lions on Zebra Prey

Amboseli Ecosystem

Predators of Amboseli Park

Amboseli: Change in Patterns of Destruction Same transects, 1975 and 2002 Bones / Individual Increased Body Size HR, RO GAZ, IM WB, CW BF HP, RH EL ZB GF

Diverse predators Lions dominant Few hyenas Lions absent Hyenas increasing Many hyenas Few lions Abundant carcasses Low damage levels Abundant carcasses Few zebra deaths Fresh carcasses rare 71% decrease in bones High damage levels EcosystemTaphosystem Amboseli

Hyena dominance and intraspecific competition is driving the change in carcass and bone survival.

Working hypothesis: If the top predator controls the destruction patterns of prey skeletons, then Laikipia 2002 should be more similar to Amboseli 1975 than Amboseli LaikipiaAmboseli Lion Hyena Different Ecosystems Different Times

Ambo 1975Ambo 02-03Laikipia 02 Bones / MNI Average Bones per MNI

Zebra Skeletal Part Survival Amboseli 1975 and vs. Laikipia 2002 Observed / Expected Skull Jaw (hemi) Vertebrae Ribs Scapula Humerus Radius/ulna Metacarpal Innominate Femur Tibia Metatarsal Patella Podials Phalanges Laikipia 02 MNI = 27 Ambo 1975 MNI = 45 Ambo MNI = 36 ForelimbHindlimb

WholeProx.– Distal Pair Shaft only Prox. only Prox. + Shaft Distal + Shaft Distal only Frequency Completeness of Humerus and Femur Laikipia 02 (N = 9) Ambo 75 (N = 48) Ambo (N = 17)

D: Fragments only B: Moderate: marginal gnawing; one end absent A: Minimal: tooth marks, scoring C: Heavy: both ends gnawed or absent Damage Categories

Damage to Humerus and Femur No Damage A Minimal Frequency Increasing damage Ambo 75 (N = 48) Ambo (N = 17) Laikipia 02 (N = 9) B Moderate C Heavy D Fragments

Adults vs. Juveniles Ambo 1975Ambo Laikipia 02 MNI Adult Juvenile

LaikipiaAmboseli Lion Hyena Dominant Predator

Conclusions Laikipia 2002 bone assemblage more similar to Amboseli than to Amboseli Our prediction is not supported. Lion vs. hyena dominance does not leave a clear taphonomic signal in the bone assemblage based on the variables we used. New Hypothesis: Damage levels may be better indicators of overall predator pressure on the prey populations than the signature of the dominant predator(s).

Skeletal part survival affected by: bone-processing capabilities of predators …but also probably by: intraspecific competition for prey predator social structure predator diversity Carcass availability and damage patterns can change over decades.

Carcasses (and prey) available to early hominins would have varied greatly in time and space because of variablity in predator consumption of carcasses. Recognition of this variability could have been an important adaptive strategy for meat-seeking hominin individuals and groups.

With Thanks to: The National Museums of Kenya The Kenya Wildlife Service The National Geographic Society David Western, Dorothy Dechant, Richard Leakey, and all the individuals who have helped with Amboseli bone research Fulbright-Hays Fellowship to B. Pobiner Sweetwaters Game Reserve, Laikipia, Kenya