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Revista Catalana dOrnitologia 28:40-44, 2012

Nota Curta /Short Note

Harpy Eagle Harpia harpyja preying on

an Ursine Howler MonkeyAlouattaarctoidea in northeastern VenezuelaBernardo Urbani, John Kvarnbck & Mathas R. Gonzlez-Alentorn

This study provides a detailed description of a rare predatory event concerning a juvenileUrsine Howler Monkey Alouatta arctoidea captured and consumed by a sub-adult HarpyEagle Harpia harpyja. During ca. 30 min., we were able to observe the behaviour of the eagle

from the moment in which the howler group began screaming until the raptor began to feedon its prey. The observation took place close to the northwestern limit of the Orinoco RiverDelta (Venezuela) and we were able to capture the first ever photographs of a harpy eagleconsuming a howler monkey. This record contributes to our knowledge of how raptors processlarge-bodied arboreal mammals.

Key words: Harpy Eagle, Harpia harpyia, predatory attack, Raptor, Falconid, Platyrrhine,South America

Bernardo Urbani*, Centro de Antropologa, Instituto Venezolano de Investigaciones Cientficas.Apartado 66.755, Caracas 1061-A, Venezuela.John Kvarnbck, Kvarnbck Birding. Caracas, Venezuela.Mathas R. Gonzlez-Alentorn, Calle San Antonio 74A, La Victoria de Acentejo, Tenerife,Spain.

*Corresponding author: [email protected]

Received: 15.04.12; Accepted: 26.07.12 / Edited by O. Gordo

To date, few predatory events concerning pri-mates have ever been recorded (Cheney &Wragham 1987). This might be due to the factthat they occur quickly and not very frequently(Isbell 1994, Urbani 2005, Ferrari 2009). Isbell(1994) has suggested that primates are onlyvery rarely preyed upon by aerial and terrestrialpredators due to the differences in habitat useby prey and predators. Nevertheless, the factthat potential arboreal prey items frequent theupper parts of trees and unfamiliar parts of theforest make them more vulnerable to predators.Harpy Eagles (Harpia harpyja) have been reportedto be important predators of atelines in generaland howlers in particular (Di Fiore 2002, Urbani2005, Ferrari 2009). The aim of this report is todescribe the process of predation of an ateline bya Harpy Eagle, to present a photographic account

of the event, and to explore how our informationdiffers or otherwise from previously publishedreports of howler predation by raptors.

Material and methods

A Harpy Eagle was encountered, observed andphotographed at a distance of ca. 40 m (visualestimation) as it preyed on an Ursine HowlerMonkey Alouatta arctoidea. The observationtook place on the Guarapiche River near CaoColorado, approximately 35 km northeast ofMaturin (state of Monagas, NE Venezuela,95458N, 625449W) at 5 m a.s.l. The obser-vation was recorded in an area with a matrix oftropical riverine lowland rainforest and a varzeasecondary forest. Other raptors occur in the

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Revista Catalana dOrnitologia 28 (2012)

area (e.g. Spizaetus ornatus, Leptodon cayanensis,and Chondrohierax uncinatus), as well as otherprimates such as the Wedge-capped Capuchinmonkey Cebus olivaceus.

Swarowski 8x42 binoculars and a Swarovski

80-mm telescope were used during the observa-tion. Behavioural data was collected ad libitum(Martin & Bateson 2007). In addition, a KodakZ650 digital camera (6.1 Mp) was fitted to thetelescope to photograph the event. A sequenceof four frames was selected and is shown below(Figure 1; see the Supplementary material for acomplete sequence of 24 frames: www.ornitolo-gia.org/ca/queoferim/divulgacio/publicacions/rco/28_40_44.pdf).

Results

On 18 May 2007, a dry day, at 150 m from theriver on a forested riverbank, we were surprisedby a nearby and unusually powerful howlerscream. At 09:15 h, we located a Harpy Eaglewith a captured howler monkey, its presencecausing approximately 10 other howlers tovocalize loudly at a distance of 15 m. Once thecapture was successfully completed, the howlersstopped screaming and the group moved away,leaving the Harpy Eagle to begin consuming thecorpse. The predatory event was observed for aperiod of around 30 min. The event took placeat mid-storey level of a tangled tree around 8 mabove ground level. The eagle did not respond tothe presence of human observers. This is the firstreport of this raptor species from the Venezuelanstate of Monagas (Redman 2008).

The Harpy Eagle was a sub-adult male, itsage being based on the moult of its upper wing-coverts; sex was determined, above all, by thesize of its talons and legs and its smaller bodysize (females are larger). The howler was aged asjuvenile by its body size, which was intermediatebetween a full adult individual and an infant.

During feeding (Figure 1), the Harpy Eagleclasped the torso of the primate with its claws.At first, the eagle seemed to squeeze the monkeyas it trampled on its body before beginning tofeed. The bird often changed the position of itstalons while manipulating the monkey and wasfirst observed to bite the monkey near its neck.Whilst biting, portions of hair were observedin the Harpy Eagles beak. When the eagle bit

the monkey, it balanced its body by placing itstail midway in relation to its bodys horizontalplane. At times, the eagle stopped feeding andremained motionless on the corpse (Figure 1,Supplementary material).

Discussion

It has been known since the end of the nine-teenth century that Harpy Eagles attack bothsloths and monkeys in Venezuela (Goering1893). Specific cases of predation on howlershave also been reported. M. Marquina (pers.comm.) observed a Harpy Eagle consuming anadult Ursine Howler Monkey in April 1986 in

the rainforest of the Guatopo National Park,central Venezuela. Guyanan Howler MonkeysAlouatta macconelli in Venezuela have beenreported apparently as prey for a jaguar on anisland of Lake Guri, state of Bolvar (Peetz etal. 1992), and captured by a Harpy Eagle inthe southeast of this state (A. Crease pers.comm.). In 1989, lvarez-Cordero (1996) foundpostcranial elements of Guyanan Howlers in aHarpy Eagle nest in Venezuelan Guayana. Inan account of the range of the Harpy Eaglein northeastern Venezuela, Redman (2008)reports on this observation whereby the eaglewas standing on a monkey that had presum-ably been caught just moments before... [andwas] tearing off chunks of flesh with its hugebill... Our report provides novel informationon these events in northern South America,and Venezuela.

Although anecdotal data must be inter-preted with caution when attempting to explainbehavioural and evolutionary phenomena, itnevertheless still is a way of understanding rarelyrecorded behaviour (Urbani & Garber 2002,Sarringhaus et al. 2005). Interestingly, some pat-terns do emerge from the few observed eventsof raptors preying on howlers (papers cited inDi Fiore 2002, Urbani 2005, Ferrari 2009).First, all such raptors were Harpy Eagles. Theserecords are from field observations (Peres 1990,Sherman 1991, Touchton et al. 2002, Ferrari2010, Marquina pers. comm., this study, and acapture attempt reported by Eason 1989) andfrom examinations of remains found in HarpyEagle nests (Izor 1985, Retting 1991, lvarez-Cordero 1996, Ford & Boinski 2007). Ferrari

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Figure 1. Harpy Eagle preying upon an Ursine Howler Monkey.Harpia depredant una Mona Udoladora.

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(2009) suggests that the size of the talons andfeet (approximately 10 cm width) of this raptormay in fact constrain the minimum size of theirprey. Field data indicate that this raptor selectslarge-sized monkeys as prey (Di Fiore 2002,

Urbani 2005, Ferrari 2009) and thus will oftenpredate on howlers given that these monkeys areamong the largest of all New World primates.Furthermore, it has been found that sub-adultand adult howlers, i.e. the largest individuals,are often the targets of attacks (Di Fiore, 2002,Urbani 2005, Ferrari 2009). Our record consistsof a sub-adult Harpy Eagle capturing a juvenilehowler monkey and there may be a correspond-ence between the relative small body size of bothyoung individuals. In addition, sexual dimor-

phism in the Harpy Eagle (males are smaller thanfemales) might also influence prey selection andsize (R. Muiz-Lpez, pers. comm.).

A second issue is how Harpy Eagles feed onhowlers. In the few available accounts, HarpyEagles are reported to prefer the ventral area ofthe corpse (Sherman 1991, and inferred fromRettig 1978). Nevertheless, in our observationthe area around the neck was first attacked. Adescription of how howlers are seized by HarpyEagles has been given by Touchton et al. (2002).In a photographic study, Springer et al. (2011)provide information on the consumption of aBrown-throated Sloth Bradypus variegatus by aHarpy Eagle: the eagle tore off flesh and movedaround on the corpse less and less as feedingprogressed, a detail that we also observed. Wetoo noted that once the prey had been seized,the Harpy Eagle seemed to squeeze its prey whilstit walked on top of it.

Previous reports have noted the howlingreactions by monkeys before, during and/or afteran aerial attack (e.g.Alouatta palliata: Touchtonet al. 2002,Alouatta puruensis: Peres 1990) and,indeed, the observed group of Ursine HowlerMonkey in our case did howl during the attack.Loud vocalization make howlers easier to detectand capture and we suggest that this vocal be-havior, common resting behavior in this species,and the fact that howlersare both large-bodiedand, in some species, conspicuously coloured(see Ferrari 2009), render these monkeys morenoticeable and easier to capture.

Finally, according to Peres (1990) and Sher-man (1991), predation by Harpy Eagles may actas a selective pressure on the structure of howler

populations. However, anecdotal reports can-not be used to fully support such evolutionaryconclusions. Thus, more field data still need tobe gathered and experimental field studies con-ducted if we are to study and test this contention.

Acknowledgements

We would like to thank the editor, Oscar Gordo, forhis suggestions and the three anonymous reviewerswho helped improve the first version of this manu-script. B. Urbani would also like to acknowledge thesupport received from the Venezuelan Institute forScientific Research. J. Kvarnbck and M. R. Gonzlez-Alentorn are grateful for the cooperation from theVenezuelan Ornithological Union. Thanks are also

due to Anthony Crease, Miguel Marquina and RuthMuiz-Lpez for their information, and to Nuria Mar-tn, Nigel Redman and Tor Kvarnbck for their help.All photographs by Mathas R. Gonzlez-Alentorn.

Resum

Depredaci duna Mona UdoladoraAlouatta arctoidea per una Harpia Harpiaharpyja al nord-est de Veneuela

En aquest estudi es fa una descripci minuciosa dunfenomen rar, com s la depredaci dun juvenil deMona Udoladora Alouatta arctoidea per un mascledHarpia Harpia harpyja subadult. Durant aproxima-dament mitja hora, es va observar el comportamentde lguila des que el grup de mones estava udolantfins que lHarpia va ingerir la presa. A ms, es vanrealitzar les primeres fotografies de tot el procs. Lesobservacions es van realitzar prop del lmit nord-oestdel delta del Orinoco, Veneuela. Aquest estudi pre-tn esbrinar com els rapinyaires processen mamfersarboris grans.

Resumen

Depredacin de un Mono AulladorAlouatta arctoidea por parte de unaArpa Harpia harpyja en el noreste deVenezuela

Este trabajo hace una descripcin detallada de unevento raro de depredacin de un juvenil de MonoAulladorAlouatta arctoideacapturado y consumido porparte de un macho de Arpa Harpia harpyja subadulto.Durante aproximadamente 30 minutos, se observ elcomportamiento del guila desde que el grupo de mo-nos estaba gritando hasta que el arpa ingera la presa.

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Se realiz la primera serie fotogrfica de una arpa con-sumiendo un mono aullador. El evento ocurri cercadel lmte noroeste del Delta del Orinoco, Venezuela.Este estudio contribuye a comprender mejor cmo unrapaz procesa un mamfero arbreo de gran tamao.

References

lvarez-Cordero, E. 1996. Biology and conservationof the Harpy Eagle in Venezuela and Panama. Ph.Ddissertation. Gainesville: University of Florida.

Cheney, S. & Wragham, R. 1987. Predation. InSmuts B.B., Cheney R.M., Seyfarth P.M., Wrang-ham R.W. & Struhsaker T.T. (eds.): Primatesocieties. Pp. 227239. Chicago: University ofChicago Press.

Di Fiore, A. 2002. Predator sensitive foraging in atel-ine primates. In Miller, L.E. (ed.): Eat or be eaten.Predator sensitive foraging among primates. Pp.242-268. Cambridge: Cambridge University Press.

Eason, P. 1989. Harpy Eagle attempts predation onadult howler monkey. Condor91: 469470.

Ferrari, S.F. 2009. Predation risk and antipredatorstrategies. In Garber P.A., Estrada, A., Bicca-Marques, J.C., Heymann E.W. & Strier K.B. (eds.):South American primates: Comparative per-spectives in the study of behavior, ecology, andconservation. Pp. 251277. New York: Springer.

Ford, S.M. & Boinski, S. 2007. Primate predationby Harpy Eagles in the Central Suriname NatureReserve.Am. J. Phys. Anthropol. Suppl. 44: 109.

Goering, A. 1893. Vom Tropischen Tieanden zumEwige Schnee. Eine Malerische Schilderung desSchnsten Tropenlandes. Venezuela. Leipzig:Adalbert Fischers Verlag.

Isbell, L.A. 1994. Predation on primates: Ecologicalpatterns and evolutionary consequences. Evol.Anthrop. 3: 6171

Izor, R.J. 1985. Sloths and other mammalians preyof the Harpy Eagle. In Montgomery G.G. (ed.).The evolution and ecology of armadillos, slothsand vermilinguas. Pp. 343346.Washington DC:Smithsonian Institute Press.

Martin, B. & Bateson, P. 2007. Measuring behaviour.An introductory guide. Cambridge: CambridgeUniversity Press.

Peetz, A., Norconk, M.A. & Kinzey, W.G. 1992.Predation by jaguar on howler monkeys (Alouattaseniculus) in Venezuela. Am. J. Primatol. 28:223228.

Peres, C.A. 1990. A Harpy Eagle successfully capturesan adult male red howler monkey. Wilson Bull.102: 560561.

Redman, N. 2008. Harpy Eagle Harpia harpyja: Anew record for Monagas state, Venezuela. Cotinga29: 169.

Rettig, N.L. 1978. Breeding behavior of the HarpyEagle, Harpia harpyja. Auk95: 629643.

Sarringhaus, L.A., McGrew, W.C. & Marchant,L.F. 2005. Misuse of anecdotes in primatology:lessons from citation analysis. Am. J. Primatol.65: 283288.

Sherman, P.T. 1991. Harpy Eagle predation on a redhowler monkey. Folia Primatol. 56: 5356.

Springer, M.T., Nielsen, C.K., Carver, A.D. & Cor-rea, N.J. 2011. Harpy Eagle (Harpia harpyja) feed-ing behavior on a brown-throated three-toed sloth(Bradypusvariegates).J. Raptor Res. 45:100-103.

Touchton, J.M., Hsu, Y. & Palleroni, A. 2002. Forag-ing ecology of reintroduced captive bred subadultHarpy Eagle (Harpia harpyja) on Barro ColoradoIsland, Panama. Ornitol. Neotrop. 13: 365379.

Urbani, B. 2005. The targeted monkey: a re-eval-uation of predation on New World primates. J.Anthrop. Sc. 83:89109.

Urbani, B. & Garber P. A. 2002. A stone in theirhands are monkeys tool users? Anthropologie(Brno) 40:183191.

Figure S1. Complete sequence of 24 frames of an Ursine Howler monkey preyed upon by a Harpy Eagle.Seqncia completa de 24 imatges duna Mona Udoladora depredada per una Harpia.

Supplementary material / Material suplementri

Supplementary material may be found in the online version of this article. /Es pot trobar materialsuplementari a la versi en lnia daquest article.

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Supplementary material / Material suplementri

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Figure S1. Complete sequence of 24 frames of an Ursine Howler monkey preyed upon by a Harpy Eagle.Seqncia completa de 24 imatges duna Mona Udoladora depredada per una Harpia.

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