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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. Flesh slicer. Bone crusher. Goals:

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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


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Flesh slicer

Bone crusher

Goals:

Test the effects of different dominant carnivores on

recent bone assemblages

Impact on models of carcass and prey availability for

early hominins


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Laikipia

Amboseli


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Laikipia and Amboseli: Live Census Data

0.45

Laikipia

0.40

Amboseli 1970's

0.35

0.30

Frequency

0.25

0.20

0.15

0.10

0.05

0.00

eland

giraffe

buffalo

impala

elephant

hartebeest

beisa oryx

black rhino

wildebeeste

Grant's gazelle

Burchell's zebra

Thomson's gazelle


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What is the taphonomic impact of different top predators?

Different Ecosystems

Laikipia

Amboseli

2002

X

X

Different Times

1975

X

12 transects

11 transects


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  • 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




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Laikipia Lions

on Zebra Prey




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Amboseli: Change in Patterns of Destruction

Same transects, 1975 and 2002

1975

Bones / Individual

2002

HR, RO GAZ, IM WB, CW BF HP, RH EL

ZB GF

Increased Body Size


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Amboseli

Ecosystem

Taphosystem

  • Diverse predators

  • Lions dominant

  • Few hyenas

  • Abundant carcasses

  • Low damage levels

1975

1990

2002-

2003

  • Lions absent

  • Hyenas increasing

  • Abundant carcasses

  • Few zebra deaths

  • Fresh carcasses rare

  • 71% decrease in bones

  • High damage levels

  • Many hyenas

  • Few lions



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Working hypothesis: change in carcass and bone survival.

If the top predator controls the destruction patterns of

prey skeletons, then Laikipia 2002 should be more similar to

Amboseli 1975 than Amboseli 2002-03.

Different Ecosystems

Laikipia

Amboseli

2002

Lion

Hyena

Different Times

1975

Lion


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Average Bones per MNI change in carcass and bone survival.

16.00

14.00

12.00

10.00

Bones / MNI

8.00

6.00

4.00

2.00

0.00

Ambo 1975

Ambo 02-03

Laikipia 02


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Laikipia 02 MNI = 27 change in carcass and bone survival.

Ribs

Skull

Tibia

Femur

Patella

Podials

Scapula

Humerus

Vertebrae

Metatarsal

Phalanges

Jaw (hemi)

Metacarpal

Innominate

Radius/ulna

Zebra Skeletal Part Survival

Amboseli 1975 and 2002-3 vs. Laikipia 2002

0.45

0.40

Ambo 1975 MNI = 45

Ambo 2002-3 MNI = 36

0.35

0.30

0.25

Observed / Expected

0.20

0.15

0.10

0.05

0.00

Forelimb

Hindlimb


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Laikipia 02 (N = 9) change in carcass and bone survival.

Completeness of Humerus and Femur

0.60

Ambo 75 (N = 48)

Ambo 02-03 (N = 17)

0.50

0.40

Frequency

0.30

0.20

0.10

0.00

Whole

Prox.–

Distal

Pair

Shaft

only

Prox.

only

Prox.

+

Shaft

Distal

+

Shaft

Distal

only


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Damage Categories change in carcass and bone survival.

A: Minimal: tooth marks,

scoring

B: Moderate: marginal

gnawing; one end absent

C: Heavy: both ends gnawed or absent

D: Fragments only


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0.70 change in carcass and bone survival.

Laikipia 02 (N = 9)

0.60

0.50

0.40

0.30

0.20

0.10

0.00

Increasing damage

Damage to Humerus and Femur

Ambo 75 (N = 48)

Ambo 02 03 (N = 17)

Frequency

A

Minimal

B

Moderate

C

Heavy

D

Fragments

No

Damage


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Adult change in carcass and bone survival.

Juvenile

Adults vs. Juveniles

35

30

25

20

MNI

15

10

5

0

Ambo 1975

Ambo 02 - 03

Laikipia 02


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Laikipia change in carcass and bone survival.

Amboseli

Dominant Predator

Lion

2002-03

Hyena

1975

Lion


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Conclusions change in carcass and bone survival.

Laikipia 2002 bone assemblage more similar to Amboseli 2002-03 than to Amboseli 1975.

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).


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  • Skeletal part survival affected by: change in carcass and bone survival.

  • 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.


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Carcasses (and prey) available to early change in carcass and bone survival.

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.


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With Thanks to: change in carcass and bone survival.

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


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