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THE WILSON JOURNAL OF ORNITHOLOGY • Vol. 123, No. 2. June 2011 
The Wilson Journal of Ornithology 123(2):404—408, 2011 
Harpy Eagle-Primate Interactions in the Central Amazon 
Bryan Bernard Lenz 13 and Alaercio Marajo dos Reis 2 
ABSTRACT.—We describe the successful predation 
of a black-bearded saki monkey ( Chiropotes sutunas 
chiropotes ) by a Harpy Eagle ( Harpia harpyja ) in the 
Brazilian Amazon and briefly recap two past Harpy 
Eagle-primate predation interactions. The physiological 
limitations that raptor anatomy places on individuals 
during predation attempts are considered along with 
escape behaviors used by primates to exploit these 
limitations to increase their chances of survival. In 
particular, we focus on primate flight paths and startle 
vocalizations. Received 18 October 2010. Accepted 14 
January 2011. 
Predation by Harpy Eagles (Harpia harpyja) 
and predation on primates are rarely observed 
events. Raptor predation on primates can have 
strong impacts on primate group size and 
composition (e.g., Crowned Eagles [Stephmoae- 
tus coronatus]-, Struhsaker and Leakey 1990). 
even at rates as low as one successful kill per year 
(Janson 1992). Botched attacks can potentially be 
fatal for raptors (e.g., Jones et al. 2006) and. as a 
result, what happens during predation interactions 
also has evolutionary significance for raptor 
species apart from the obvious benefits of the 
successful capture of prey. The importance of 
these events, in concert with how rarely they are 
witnessed, makes it crucial that each observation 
is carefully reported so that, over time, knowledge 
of raptor-primate interactions during predation 
events can be accumulated. 
The objectives of this paper are to: (1) describe 
the successful predation of a juvenile female 
black-bearded saki monkey (Chiropotes satanas 
chiropotes ) by a Harpy Eagle, and (2) discuss 
what these observations suggest about predator 
and prey strategies. More specifically, we focus 
on the physiological limitations of raptors and the 
way primate prey might adapt their flight paths 
'Tulane University, Department of Anthropology, 101 
Dinwiddie Hall, New Orleans, LA 70118. USA. 
‘Biological Dynamics of Forest Fragments Project, 
Institute Nacional dc Pesijuisas de Amazonia (INPA), 
Caixa Postal 47S, Manaus, Amazonas, CEP 69011-970 
Brasil. 
Corresponding author; e-mail:bblenz@gmail.com 
and vocalizations to exploit these limitations. We 
also discuss two past Harpy Eagle-primate 
interactions and note two observations of Harpy 
Eagles with primate carcasses. 
OBSERVATIONS 
All observations were made in continuous, 
closed canopy terra fume forest at the Biological 
Dynamics of Forest Fragments Project (BDFFP). 
80 km north of Manaus, Brazil. This study site has 
been described in detail by Gascon and Bierre- 
gaard (2001). 
Successful Predation Event .—The successful 
predation of a juvenile female black-bearded saki 
occurred during primate surveys on 21 February 
2010 al 02 21.211' S, 60 06.452' W in undis¬ 
turbed forest at the Diinona Ranch of the BDFFP: 
the canopy height was —30 m. The Harpy Eagle 
left the monkey on the ground before later 
returning for it, providing us with the rare 
opportunity to closely examine the pre-consump- 
lion carcass of a Harpy Eagle kill. At 0911 hrs. 
during his approach to the site, the first observer 
heard the alarm calls of the Red-throated Caracara 
(lhycrer americanus) followed by a single loud 
black-bearded saki scream. This saki call was 
followed by standard black-bearded saki alarm 
calls from multiple individuals and the alarm calls 
of several White-throated Toucans (Rhamplwslos 
tucanus). Another saki scream was heard on or 
near the ground 15-25 sec after the first scream 
and a 1-m tall sapling was seen shaking as the 
observ er arrived. An adult male Harpy Eagle flew 
from the ground at this location to perch 5 m 
above the ground in an understory tree 30 m 
distant. 
At 0925 hrs the Harpy Eagle flew away. The 
Red-throated Caracaras continued to alarm call 
while diving at the eagle from above as it took 
flight. Wc located the tip of a broken Harpy Eagle 
tail leather and the body of a large juvenile femme 
saki lying on its side on the ground. There were 
two sets of puncture wounds on the saki. one from 
each of the eagle’s feet, and no other apparent 
wounds, although blood was coming from the 
anus. The wounds indicate the eagle attacked 
