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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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slide1
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

slide2
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

slide3
Laikipia

Amboseli

slide4
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

slide5
What is the taphonomic impact of different top predators?

Different Ecosystems

Laikipia

Amboseli

2002

X

X

Different Times

1975

X

12 transects

11 transects

slide6
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
slide9
Laikipia Lions

on Zebra Prey

slide12
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

slide13
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
slide14
Hyena dominance and intraspecific competition is driving the change in carcass and bone survival.
slide15
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 2002-03.

Different Ecosystems

Laikipia

Amboseli

2002

Lion

Hyena

Different Times

1975

Lion

slide16
Average Bones per MNI

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

slide17
Laikipia 02 MNI = 27

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

slide18
Laikipia 02 (N = 9)

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

slide19
Damage Categories

A: Minimal: tooth marks,

scoring

B: Moderate: marginal

gnawing; one end absent

C: Heavy: both ends gnawed or absent

D: Fragments only

slide20
0.70

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

slide21
Adult

Juvenile

Adults vs. Juveniles

35

30

25

20

MNI

15

10

5

0

Ambo 1975

Ambo 02 - 03

Laikipia 02

slide22
Laikipia

Amboseli

Dominant Predator

Lion

2002-03

Hyena

1975

Lion

slide23
Conclusions

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).

slide24
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.
slide25
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.

slide26
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

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