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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: - PowerPoint PPT Presentation
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Differing impact of carnivores on bone assemblages in two
East African Ecosystems
Anna K. BehrensmeyerDepartment of Paleobiology, Smithsonian Institution
Briana L. PobinerDepartment 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 slicer Bone crusher
Amboseli
Laikipia
0.00
0.05
0.10
0.15
0.20
0.25
0.30
0.35
0.40
0.45
wildeb
eeste
Burch
ell's
zebr
a
Grant
's ga
zelle
Thom
son's
gaz
elle
impa
la
buffa
lo
eleph
ant
giraf
fe
harte
bees
t
beisa
ory
x
black
rhino
eland
Fre
qu
ency
Laikipia
Amboseli 1970's
Laikipia and Amboseli: Live Census Data
Laikipia Amboseli
1975
2002
X
X X
Different Ecosystems
Dif
fere
nt T
imes
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 Park1975 - 2003
Amboseli: Change in Patterns of Destruction Same transects, 1975 and 2002
Bo
nes
/ Ind
ivid
ual
0
5
10
15
20
25
30
35
1 2 3 4 5 6
Increased Body Size
HR, RO GAZ, IM WB, CW BF HP, RH EL ZB GF
1975
2002
• Diverse predatorsLions dominant
Few hyenas
Lions absent• Hyenas increasing
• Many hyenas• Few lions
1975
1990
2002-2003
• Abundant carcasses• Low damage levels
•Abundant carcassesFew zebra deaths
• Fresh carcasses rare• 71% decrease in bones
High damage levels
Ecosystem Taphosystem
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 2002-03.
Laikipia Amboseli
1975
2002
Lion
Lion Hyena
Different Ecosystems
Dif
fere
nt T
imes
0.00
2.00
4.00
6.00
8.00
10.00
12.00
14.00
16.00
Ambo 1975 Ambo 02-03 Laikipia 02
Bo
nes
/ MN
I
Average Bones per MNI
Zebra Skeletal Part SurvivalAmboseli 1975 and 2002-3 vs. Laikipia 2002
Ob
serv
ed
/ E
xp
ecte
d
Sku
ll
Jaw
(h
emi)
Ve
rteb
rae
Rib
s
Sca
pul
a
Hum
eru
s
Rad
ius/
uln
a
Met
aca
rpal
Inno
min
ate
Fe
mu
r
Tib
ia
Met
ata
rsal
Pa
tella
Po
dial
s
Ph
alan
ges
0.00
0.05
0.10
0.15
0.20
0.25
0.30
0.35
0.40
0.45Laikipia 02 MNI = 27
Ambo 1975 MNI = 45Ambo 2002-3 MNI = 36
Forelimb Hindlimb
0.00
0.10
0.20
0.30
0.40
0.50
0.60
Whole Prox.–DistalPair
Shaft only
Prox. only
Prox. +
Shaft
Distal+
Shaft
Distal only
Fre
quen
cyCompleteness of Humerus and Femur
Laikipia 02 (N = 9)
Ambo 75 (N = 48)
Ambo 02-03 (N = 17)
D: Fragments only
B: Moderate: marginalgnawing; one end absent
A: Minimal: tooth marks,scoring
C: Heavy: both ends gnawed or absent
Damage Categories
Damage to Humerus and Femur
0.00
0.10
0.20
0.30
0.40
0.50
0.60
0.70
No Damage
AMinimal
Fre
qu
en
cy
Increasing damage
Ambo 75 (N = 48)
Ambo 02 03 (N = 17)
Laikipia 02 (N = 9)
BModerate
CHeavy
DFragments
Adults vs. Juveniles
0
5
10
15
20
25
30
35
Ambo 1975 Ambo 02 - 03 Laikipia 02
MN
I
Adult
Juvenile
Laikipia Amboseli
1975
2002-03
Lion
Lion Hyena
Dominant Predator
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).
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 KenyaThe Kenya Wildlife Service
The National Geographic Society
David Western, Dorothy Dechant, Richard Leakey, andall the individuals who have helped with Amboseli bone research
Fulbright-Hays Fellowship to B. PobinerSweetwaters Game Reserve, Laikipia, Kenya