The Uncertainty of Data and Dehorning Black Rhinos by joelbergerconservation

Society for Conservation Biology

The Uncertainty of Data and Dehorning Black Rhinos Author(s): Joel Berger, Carol Cunningham, A. Archie Gawuseb Reviewed work(s): Source: Conservation Biology, Vol. 8, No. 4 (Dec., 1994), pp. 1149-1152 Published by: Blackwell Publishing for Society for Conservation Biology Stable URL: http://www.jstor.org/stable/2386586 . Accessed: 09/11/2011 10:59 Your use of the JSTOR archive indicates your acceptance of the Terms & Conditions of Use, available at . http://www.jstor.org/page/info/about/policies/terms.jsp JSTOR is a not-for-profit service that helps scholars, researchers, and students discover, use, and build upon a wide range of content in a trusted digital archive. We use information technology and tools to increase productivity and facilitate new forms of scholarship. For more information about JSTOR, please contact support@jstor.org.

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TheUncertainty ofDataand BlackRhinos Dehorning JOEL BERGER Programin Ecology,Evolution,and ConservationBiology of Nevada University Reno,NV 89512, U.S.A.

CAROL CUNNINGHAM and Resource Sciences Departmentof Environmental of Nevada University Reno,NV 89512, U.S.A.

A. ARCHIE GAWUSEB P.O. Box 220 Khorixas,Kunene Province Namibia

Wildblackrhinosare approachingextinctionfasterperhaps than any other Africanmammal. In Namibia's desertstheyoccur at low densities,have home ranges up to 2000 km2,and have birthintervalsthatexceed 30 months.Clearly,they are difficultto study.Practical will alwaysbe placed on samplesizeswhich, constraints in turn,limitthe robustnessof generalizations.Nevertheless,the internationalconservationcommunityhas not writtenoffthisflagshipspecies, and the luxuryof awaitingthe resultsof 10-yearstudiesis somethingthat neitherCITES nor concerned groupscan afford.Loutit and Montgomery (1994) suggestthatdehorningmaybe needed to develop a sustainablehornharvestto save the world's remainingwild rhinos,and they challenge a numberof pointsreportedin Bergeret al. (1993). We do not take issue with the possibilitythatgovernment harvestingand sale of rhinohorn mightpossiblyhelp eliminatethe poaching industry;however, Loutitand Montgomerydo not offera rationalconsiderationof ofdehorning.Instead, issuesassociatedwiththeefficacy theirresponse is taintedby a political agenda to dis-

Paper submittedMay 10, 1994; revisedmanuscriptacceptedJuly6, 1994.

creditour findingscoupled withthe goal of stockpiling dehornedhornforlatertrade.Forinstance,althoughwe reportedthatone of us was convictedforfelonyrhino poaching(Bergeret al. 1993:922), Loutitand Montgomery(1994) feelthe need to drivehome the point "One of the authors ... was arrested and convicted." What

they fail to say is that because our coauthor,Archie Gawuseb,was employedby themwhen the poaching occurred, he knew the locations of horned and dehornedrhinos,optingforthe former. Loutitand Montgomeryseek clarificationabout our estimatesof horngrowth.Althoughmethodswere provided (Bergeret al. 1993) and additionalexplanationis offeredelsewhere (Berger & Cunningham1994a), a briefcommentmay help remove ambiguityabout the limitationsof our data. We derivedannual growthby dividingthe totalsize ofregrownhorn(converted subsequentlyto mass) by timesince removal.These are of course estimatesonly,as measurementerrorwill always exist.Does it reallymatterwhethermale hornsregrow at 5.3 or 5.5 cm per year?Loutitand Montgomeryalso indicatethatto assess the economic efficacyofdehorningthe riskof capture(forpoachers) mustbe balanced against the incentive to poach. Our lack of data on prices receivedby middlemenshould not detractfrom 1149 ConservationBiology,Pages 1149-1152 Volume 8, No. 4, December 1994

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BlackRhinos Dehorning

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our major assertions:horns grow fastand are wortha good deal of money.Perhapshornscould be used sustainably.Butwe are surprisedthatLoutitand Montgomery omittedciting the work of Milner-Gullandet al. (1993) which, using middlemenprices, suggestsdehorningis not as worthwhileas otherconservationactions. The remainderof our comment concerns two matters,the viabilityof dehornedblack rhinosand alternativehypothesesforthe mortality of juvenileswith dehornedmothers. The issue of whether human interventionhas enhanced the viabilityof dehornedrhinosis tricky.Loutit and Montgomeryargue thattherewas interchangebetween populationstherebyassuminga largersubpopulationthanreallyexists.We studieddiscretedehorned populationsin the Springbokand Ugab River regions and foundno evidence of interchange. Data we collated fromrecords of unmistakableindividual rhinos from 1988 to 1993 show that our dehorned studypopulationdropped 16%, from25 to 21 animals;thisincludes5 survivingcalves,9 deaths,and 4 transfers (3 were subadultfemales-25% of the cohort ofpotentiallybreedingfemales).To thenorthofa councordonfencewe focusedon a subset veterinary try-long of the larger population (about 90) of exclusively hornedanimals.Our smallsampleincreased 17%, from 10 to 12, over the same 6-yearperiod. Because the disjunct, dehorned population to the south had (1) no femaleimmigration, (2) potentiallybreedingfemalesreand a rate thatexceeded natality, moved, (3) mortality thereis no apparentneed to modifythe statementthat

"a highdegreeofuncertainty about theirlong-term populationviabilityexists"(Berger et al. 1993:923). Numeroushypothesesexistforwhy juvenile mortalitywas restrictedto areas where dehornedrhinosand spottedhyenasoverlapped.We have alreadyaddressed fourpossibilities-predation,maternalage, year of destress(Bergerand Cunningham horning,and nutritional 1994a). However,the claim thatecological conditions amongour studyareas mayhave been affecteddifferentiallyby domesticstockwarrantsattention.If livestock changed the dynamicsof the area where calves died, thenitwould be difficult to arguethatour experimental designwas balanced.We consideredthispossibilityindirectlyby suggestingthat if food availabilitydiffered among studysites,thenrhinosfromnutritionally poor areas should have been in worse conditionthan other rhinos.We contrastedbody conditionand foundthatit did not differamong areas (Berger & Cunningham to explore the idea of 1994a). But,it would be fruitful ecological similarity amongsitesfurther. To assess whether herbivorepopulations followed similarpatterns,we estimatedbiomassin each area believingthatherbivorestrackin a generalsense the available vegetation.Annualdata on thefrequencyofspringbok,kudu,giraffe, ostrich,gemsbok,and mountainzebra were compiled from126 transectsthatcovered 5106 km duringwet and dryseasons. Data were normalized by transformation using log(x + 1), which avoids the problemof havingzeroes in which the log is negative The samepatternofseasonalfluctuations in herinfinity. bivorebiomasscharacterizedeach site(Fig. 1). Seasonal

160 = Northern Site * = UgabRiver A = Springbok River

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ConservationBiology Volume 8, No. 4, December 1994

Namib Desert areas (size in km2): Northern Site (1858 km2), theSpringbokRiver (and

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(1710 km2), and the Ugab River(3418 km2). Species and mean masses (kg) as follows: springbok(37), gemsbok (210), kudu (157), mountain zebra

(276), giraffe(850), and ostrich(111). Values on thefigure are number of transects.

& Cunningham Berger

BlackRhinos Dehorning

influenceswere highlysignificant(F1,72 = 9.74, p <

0.01) but yearly (F2,72 = 0.09) or site (F1,72 = 1.40)

effectswere not. This indirectassayfailsto suggestobvious ecological differences in patternsofherbivorebiomassand itreinforcestheidea thatrhinoswere exposed to similarconditions. Loutitand Montgomery (1994) claim that"Whenthe calves died, approximately500 goats were broughtto thearea,"a statementthatis nonsense.When thecalves died remainsunknown.There was, at a minimum,an 8-monthperiod between thebirthoftwo calves and the theirmeandiscoverythattheyperished.Additionally, ing of "the area" as well as the correctnumberof domestic stock is ambiguous.We visited our 1710-km2 SpringbokRiverstudyarea seven timesin 1992-1993 and neverfoundevidence ofdomesticstockpriorto the periodwhen calves disappeared,althoughgoatsand cattle are found about 20 km to the east of water frequented by dehornedmothers.Whatseems more likely is thatLoutitand Montgomerymisinterpreted a report of a total of 493 livestock,"408 head of cattle and 85 goats" in the Ugab River (Morkel 1992) and claimed therewere 500 goats at thatriversite.The Ugab region served primarilyas our hyena-free site with dehorned mothers.Thus,thereis muchuncertainty about thetim-

SRT in 1989

durationand locationoflivestockpresingofmortality, ence (if any), and discreteeffects. Most seriousperhapsis thatLoutitand Montgomery indicatetheyhave knowledgeof only two calf deaths. The issue of whethertwo or three calves died is not pivotalto conclusionsalreadypresentedin Bergerand Cunningham(1994a). It is, however,criticalin understandingour reluctanceto accept assertionsabout the certaintyof data compiled by Save the Rhino Trust (SRT), a Namibiannongovernment organizationwhere Loutitand Montgomeryserve as directors.Our assessment of calf mortalityhas been conservativeand we deliberatelyminimizechances to inflatecalf mortality. For instance,Loutit(in Vigne 1989) claims that "the firstdehornedrhino(May-June,1989 [our insertion]) was Tammy,a pregnantcow." Neitherwe, nor any one else withwhom we talked,have any knowledgeabout thefateofthatpregnancy.Thisfemaleis one offourthat has been sympatricwith spotted hyenassince at least 1989. We discounted the possibilitythat this female gave birthto a 1989-1990 calfthatlaterdied. We did howeverrecorda mortality aftera 1992 calfbor to that female disappeared between July 1992 and February 1993. Hence, in assessing post-dehoring patternsof calfproductionand survival,we ignoredLoutit'sclaim

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Figure2. Examples of misofrhinos by Save theRhino Trust(SRT) (1989 errorsshown with 1992 corrections): Photographof Tammy, drawings of ears and associated notchpatternsassigned by SRT and correctednotch locations byNamibian Ministryof Wildlife,Conservation,and Tourism (MWCT) afterexamination of thephotograph(A); photocopy of a reversedApril, 1990 SRT photograph of Petra and calf and SRT 1989 and MWCT 1992 ofPetra's ear

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(B). The actualphoto-

graph ofPetra and calf (C) taken in February,1992. Arindicate conspicuous ear or tears Photographs byBergerand Cunningham, handwrittennames and drawings of ear notchpatternsand correctionsare photocopies fromSRT and MWCTfiles obtained withpermission in 1991 and 1992, respectively.

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BlackRhinos Dehorning

of pregnancyand it is possible that a calf was never are born.However,we mustpointout thatwhen efforts not made to discovermissinginfantsor ifcensus intervals are too widelyseparated,thenitwill be impossible will to detect the presence of calves and mortalities, unknown. remain always Loutit(in Vigne 1989:47-48) also stated that "we have been monitoringrhinosin Damaralandfornearly ten years,and believe thatwe know enough of their habitsto warrantthe resultsof removingtheirhorns," and Loutitand Montgomery(1994) maintainthattheir records"are kept continuouslyupdated throughpopuWe disagreewith each contention. lationmonitoring." Assessmentofthe successes or failuresofthedehorning strategyhingeson accurateknowledgeof individuals. The lattertaskis challengingbecause withouthorns rhinoslook verysimilar.This problem is avoidable by markersand using ear tears or notches as identifying it is unconsciorecords accurate Thus, 2). (Fig. keeping nable that 50% (8) of the dehorned animalsthat remained in 1989 were not correctlyidentifiedby Save the Rhino Trust (Fig. 2). These mistakeswent uncorrected for three years,despite the 1990 claim made subsequentto dehorningthat"Each individualrhinois monitoredby SRT and Ministryof Wildlife,Conservation,and Tourismstaffon a regularbasis to collect acfordossierswhich have been comcurate information piled ofeach rhino..." (Loutit 1990:5), a declarationin the SRT color brochure solicitingfundsfrominternational donors. Accountabilityis clearlyin the public's best interest.However,itwas not untilafterApril,1992 errorswere corrected(Fig. 2), in part thatidentification due to assistancewe rendered.The foregoingmakesit forus to place much faithin the accuracy of difficult or in the "long-term" claimsby Loutitand Montgomery monitoringrecordsof Save the RhinoTrust. indicatethattheyacFinally,Loutitand Montgomery corded us neithersponsorshipnor saw an advance copy of ofour manuscript. Theyare correct;onlytheMinistry Wildlife,Conservation,and Tourismwas given an advance copy.We apologize ifwe unintentionally implied an endorsement.But Save the RhinoTrustdid serve as one ofBerger'stwo officialconduitsfortheU.S.Agency ofInternational Developmentsupport.Loutitand Montgomeryalso providedaccess to theirfilesand engaged ofdehorningwhichis in conversationabout theefficacy whywe acknowledgedthem. Our intenthas been to clarifyclaims made by Loutit and Montgomeryabout the efficacyof dehorningblack rhinos,not to suggestthatour work is withoutits own pointsand They raised some interesting shortcomings. have done a firstrate job at bringingNamibia'sdesert

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pachydermissues to the public's eye. Nevertheless, murkyrecords,proclaimed supportfor policy action (e.g., horn trade),and a hazy view of biologicalprinciples are poor steppingstonesforbuildinga foundation upon which to conserveendangeredspecies. It maybe too earlyto tell ifdehorningis effectiveor not. But,to be circumspect,to err on the side of prudence,and to use empiricallybased data in decision-making seems far wiserthanplowingahead witha tacticthatwill neverbe fullytested,at least in Namibiawhere foreignresearchers are discouraged (Berger & Cunningham 1994b; Macilwain, 1994). No matterhow well intentioned, nongovernmentorganizationsthat deal with environmental conservationshould be guided by biological counsel ifnot by formalscientificadvisoryboards. Life at the forefront ofpublic relationsand fundraisingwill with the timespentin onalwaysnecessitatetrade-offs the-ground management.Save the RhinoTrustexemplifiesthe challengestherein.Wishingto presenta persuasive programof action in an attractivelightcan either help facilitateor block valid conservationagendas. Science should play a role in rhinoconservation. Cited Literature Berger,J., C. Cunningham,A. Gawuseb, and M. Lindeque. 1993. "Costs" and short-term survivorshipof hornlessblack rhinos.ConservationBiology7:920-924. Berger,J.,and C. Cunningham.1994a. Phenotypicalterations, evolutionarysignificantstructures,and rhino conservation. ConservationBiology8:833-840. Berger,J.,and C. Cunningham.1994b. Black rhinoconservation.Science 264:757. Loutit,B. 1990. Save the rhino.Save the Rhino Trust,Windhoek. Loutit,B., and S. Montgomery.1994. The efficacyof rhino dehorning:Too early to tell!! ConservationBiology 8:923924. Macilwain,C. 1994. Biologistsout ofAfricaover rhinodispute. Nature368:677. andJ.R. Beddington. Milner-Gulland, E.J.,N. Leader-Williams, 1993. Is DehorningAfricanrhinosworthwhile?Pachyderm 17:52-58. Morkel,P. V. 1992. Report on the death of a black rhino (Diceros bicornis bicornis) in the Ugab River.Unpublished Report.Save the RhinoTrustFiles,Windhoek. Vigne,L. 1989. Dehorningrhinosin Damaraland-A controversialissue. (Excerptsof B. LoutitfromSave the RhinoTrust Fund Newsletter53). Pachyderm12:47-48.