Capturing and Marking Greater Rheas

J. Field Ornithol., 63(2): 117-120

CAPTURING AND MARKING GREATER RHEAS

MONICA B. MARTELLAAND JOAQUINL. NAVARRO Centrode ZoologfaAplicada Universidad Nacional de Cdrdoba Casilla de correo 722 5000 Cdrdoba,Argentina Abstract.--In 1989-1990, 14 Greater Rheas(Rhea americana) were neck-collaredat COrdoba province,Argentina. Birds were stupefiedduring the night by a light-beamand then caught using'boleadoras.' The markingdevice was a numberedadjustable cattle-type PVC legband. This captureand bandingtechnique proved to be efficientand comparativelyinexpensive, and couldbe effectiveboth for otherratites and somelarge mammals with longlegs.

CAPTURAY MARCADODE I•IAND•JES(RHEA AMERICANA) Sinopsis.--En1989-1990, 14 •andfies (Rhea americana) fueron marcados (con collares) en la provinciade C6rdoba,Argentina. Las avesfueron deslumbradasdurante la nochecon un reflectory luegocapturadas usando boleadoras. Se emple6como collar una bandaplfistica ajustablenumerada, disefiada originalmente para marcarel ganadoen suspatas. Esta t&nica de capturay marcadoes eficiente y de bajocosto. Podria ser electira tanto para otrosRatites, comopara algunosmamfferos grandes que poseanpatas largas.

The Greater Rhea (Rhea americana)is one of the most conspicuous birds of the scrublandsand grasslandsof easternand central Brazil, the BolivianChaco, Paraguay, Uruguay and northernand centralArgentina southto Rio Negro (Blake 1977). In the early stagesof a studyon the ecologyand behaviorof this species, we required a techniquefor permanentlyidentifying individuals in the field. We had to deal with two problems:Greater Rheas are difficult to capturebecause of their speedand size,and the shrubsand tall grassthat aboundin our area could obstructthe view of leg-bands.In Argentina, the conventionalmethod used to catch these birds for plucking their feathers consistsof herding individuals by a trained group of 10-20 horsemenusing large drift netsand fences.We testedthis technique,but it provedtoo expensivedue to the large equipmentand skilled labor that must be involved. This paper describesan alternativemethod of captureand a numbered plastic neck-collar used to mark Greater Rheas. Greater Rheas were successfullycaptured using traditional 'boleadoras.'This deviceconsists of either two or three balls of roundedsoap- stonelined with raw leatherand fastenedfirmly to a longstrap of braided leather. These strapsare, in turn, tied togetherat their other end. We useda 'boleadoras'that had two 200-g balls and one (the handle)220-g ball, attachedto 7-mm diameterstraps that were 0.97, 0.94 and 1.26 rn long,respectively. The 'boleadoras'can be either purchasedfor about$20 (US), or easilyconstructed with fishingline weightsand nauticalrope. We carriedout the capturesduring the nightwhile the birdslay sleeping on the ground. When a rhea was detected,the vehiclewas slowedand

117 118] M. B. Martellaand J. L. Navarro J.Field Ornithol. Spring1992 • 33.5Cm.

FIGURE I. Large numberedPVC neck-collar.

its headlightswere switchedoff while the bird was spotlightedwith a 200,000-candlepowersearchlight. This light-beamgenerally dazzled the bird,giving the personstime to getout of thecar andwhirl their 'boleadoras'in the air (to givethem speed) while they swiftlyapproached the rhea to within a distanceof 10-15 m without beingperceived. When the bird stoodup andbegan to run, the 'boleadoras'were thrown toward its legs.If thethrow was accurate, the strapswound around the rhea'slegs, andit becameentangled and fell down.Immediately, it wasimmobilized and then markedwith a large numberedplastic neck-collar (described below). When released,the rhea ran far away and again adoptedthe sleepingposture. The time elapsedfrom detectionto releasewas about 10-15 min. This interval should be minimized because individuals of this speciescan die due to capture-release stress (M. C. Renteros,pers. comm.). Capturingshould be carriedout duringwinter (non-reproductivesea- son).This enhancesthe efficiencyof the methodbecause Greater Rheas join larger flocksand showless tendency to escape. We testedthis techniqueon 25-26 Jun. 1989 and 28-29 Jun. 1990 at La Panchita and La Milena ranchesin south-westernCOrdoba province. Three skilled workerswere hired and they captured14 Greater Rheas (sevenadults and sevenyoung) in 14 h of fieldwork. The majoradvantages of thistechnique are its low cost($1.50-2.50 [US] per bird) and its safety;it doesnot causeinjury to the birds.In addition,none of the Greater Rheaswe caughtshowed evidence of stress at release,or haveexhibited any subsequentalteration of behavior.Dis- advantagesare that it is suitableonly in grasslandsand its efficiency dependson the skill in the useof 'boleadoras.'This last issuedoes not limit the useof this techniqueto Argentinaand adjacentareas, however, becauseanyone could make 'boleadoras' and learn to usethem. Vol.63, No. 2 Capturingand Marking Rheas [ 119

FIGURV.2. Greater Rhea showingthe numberedneck-collar. 120] M. B. Martellaand J. L. Navarro j. FieldOrnithol. Spring 1992 The neck marking devicetested by us on rheas was a standard ad- justable,cattle-type legband (RAITE R•r)manufactured by TECIND S. A. ARGENTINA. Its costis $0.50 (US). This collar is made of flexible polyvinylchloride (PVC) and has a tightenerthat permitsadjusting its diameterfrom 8.5 to 5.5 cm. Its dimensionsare shownin Fig. 1. It is 3.7 mm thick and weighs 58 g, which is equivalentto 0.001 of the rhea's body mass.It is easily applied and, when necessary,can be adjustedor removedwith a specialpalette knife. Identifying numbers are written with a black indelibleink marker on the fiat portionof the collar. Several band colorsare available (yellow, green, orange, light blue, black and white); however,we usedonly black digits on yellow bandsbecause this color combinationhas been recommendedby other authors (Hart 1987, Ogilvie 1972). With 8 x 25 binoculars,the collarsare conspicuousin the field (Fig. 2) at distancesup to 300 m. The numbers,however, are difficult to read at distancesof more than 100 m without a telescope. The collars have been worn by two adult males kept in a 0.5-ha enclosurefor 2 yr and by wild birds for more than 1 yr. During this time, none of the marked rheas exhibited either physical damage or abnormalitiesin behavior. One captive male was observedincubating a clutch and later seen foraging with its chicks.One young bird lost an inadequatelytightened collar when it slippedover its head. The collars on all other birds remained in positionwithout indicationsof wear. The techniqueof capture describedin this paper could be used on other large animals with long legssuch as other Ratites and somemam- mals (e.g., camelids).Although neck-collarshave been used extensively for marking waterfowl, reportson the successof thesedevices have not all been favorable (Marion and Shamis 1977). Our results, however, indicateneck-collars may be appropriate for marking thoselarge species that commonlygraze in tall grass,where their legs are not visible.

ACKNOWLEDGMENTS

The Lapizondo family gave permissionfor the researchto be carried out on their prop- erties.Authorities of the C6rdobaZoological Park allowedus to test the collar on captive birds. S. M. Russell and an anonymousreviewer improved this manuscriptwith many helpfulcomments and suggestions.The Consejode InvestigacionesCient•ficas y Tecno16gicas de C6rdoba(CONICOR) providedfunds through researchgrants to M.B.M. (no. 1301/ 89 and 1572/90).

LITERATURE CITED

Bx•^x•w,E.R. 1977. A manual of neotropicalbirds. Univ. ChicagoPress, Chicago, Illinois. 674 pp. H^RT, A. D.M. 1987. Patagial tagsfor Herring Gulls: improveddurability. Ring. Migr. 8:19-26. MARION, W. R., ANDJ. D. SHAMIS. 1977. An annotatedbibliography of bird marking techniques.Bird-banding 48:42-61. OGILVIE, M.A. 1972. Large numbered leg bands for individual identification of swans. J. Wildl. Manage. 4:1261-1265. Received18 Dec. 1990; accepted11 Jul. 1991.