Coypu Project - Secretaria de Ambiente y Desarrollo Sustentable

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Management of wild life in ArgentinaThe results obtained from the application ofthese three models showed differentscenarios. Contrary to age structure analyzedabove and its probable relation to relativelyintense and persistent hunting activities,according to the MSU (and the intrinsic ratesof estimated growth) coypu populations wouldbe hardly susceptible to local extinctions.However, it is observed a slight decreasingtendency (or smaller increment) in their sizes(Nazar Anchorena, 2004), due to the fact thatthe generational time is relatively longer thanthe one mentioned by other authors (Kinler etal., 1987).In turn, just as Bodmer (personalcommunication) suggests in his Model ofUnified Crop, the simultaneous analysis of theresults provided by the MCO and the MRShint that there would be an excessive huntingactivity in at least in 40% of the coypuexploitationareas of the country. However, insome of these cases such activity would be“concealed” by “compensatory” effects of thestill broad habitat availability in most coypuexploitationareas, as well as the prominentreproductive, distributional and colonizationcapacities of the species (Bó et al., in press).Nevertheless, it should be kept in mind thatthe mentioned compensatory factors couldstop being effective if there appears anynatural or anthropic factors so far ignored,such as illnesses, modifications in thehydrologic state caused by floods (Bó andMalvárez, 1999), “extraordinary” droughtsand/or implementation of infrastructural worksfor the management of water (Bó andQuintana, 1999). These events would bringabout negative or at least uncertainconsequences for the species and the humancommunities that live on its exploitation.e) Evaluations of the physical conditionand the sanitary state of the specimens.In order to describe the physical condition orthe general state of the specimens comingfrom the different areas under study, wecalculated an index of condition as proposedby Bailey (1968) and used by Willner et al.(1979) for the M. coypus. This index is basedon the existing relation between weight andcorporal size of the specimen and it can rangefrom 0 to 10. It was observed that, in almostall the coypu-exploitation areas of the country,despite the eventual numerical compensationthat could arise from year to year, the physicalcondition of the specimens would bedeteriorated. This can be closely related toexcessive hunting activity detected by themodels of sustainability, as already described.The mean value of the index of conditionturned out to be relatively low (M = 3.61;range 2.34-5.59) if it is compared, forexample, with the values collected in a placewhere the coypu does not undergo huntingpressure (see sections below). The lowestvalues observed corresponded to thoseplaces with the greatest historic intensities ofhunting pressure. (Bó and Porini, 2003;Corriale, 2004).An analysis of fecal matter and viscera (liverand intestines) of most of the specimenscaptured was carried out in relation to theirsanitary state. As already mentioned inprevious works Moggia, 1981; Colantoni,1993), it was observed a particularly diversepresence of parasitic fauna, among which it isworth highlighting the digenea of the genusHippocrepis, Athesia and Taxorchis and somecestoda species, still in the phase ofidentification. It is also important to remark theabsence of Fasciola hepatica in all thespecimens examined (Galvani, personalcommunication).f) Analysis of the situation of the coypu inperiurban wetlands without presentexploitation activities.As an important complement to the activitiesbeing implemented in the main coypuexploitationareas of Argentina, it wasanalyzed the situation of the coypu in theBiosphere Reserve Laguna Oca of theParaguay River (Bó et al., 2004). This reserveis located in the province of Formosa. Themethodologies applied were similar to thosedescribed for the PAs for coypu-exploitation.The evaluation of the past and presentsituation of the coypu in such reserve turnedout to be useful since this is a protected areathat allows human presence and is locatednext to a densely populated city (Formosa),inserted in the valley of floods of the Paraguayriver (CMA,- 6 -
R.F.Bó, G.M. Porini, M.J. Corrialey S.M. Arias – Coypu Project2001). According to traditional maps of naturaldistribution of species, this is considered to bea typical area for coypu, although surprisinglyit is nowadays unimportant in terms of coypuexploitationactivities (Arias et al., in press).The results found, both through interviews aswell as through field studies, indicated that thecoypu was not practically found in the reserve(M = 0 individuals/ha; range 0-1,47 ind/ha.; Bóet al., 2004). Although there was an adequateavailability of habitat (though relatively smallerthan that of other wetlands in the countrycompared to water level and stability andcoverage and variety of the vegetation), themarked absence of the species would be theresult of a historic over-exploitation associatedwith the marginal economies of a great part ofthe human communities and the lack ofadequate controls. To this situation it wouldbe necessary to add the advance of the urbanborder, the action of natural predators such asthe yacaré (Caiman spp.), practically absentin most of the coypu-exploitation areas of thecountry, and the effect of large floods (Arias etal., in press). For all this, in this particularcase, it was recommended to implement aplan of population reinforcement (UICN,1998), that would contribute to the recovery ofthe coypu in the area, following (and makingothers fulfill) the guidelines of the MABProgramme (UNESCO-MAB, 1996), as wellas with offering a productive alternative for thelocal communities.g) Study of coypus population in anartificial urban wetland.This project also included habitat and lagoonpopulations studies in the Golf Course of theCity of Buenos Aires –CGCBA– and itsoutskirts (Corriale, 2004), since the effects ofcoypu activity in artificial environments werepractically unknown in our country.It was observed that the intensity of use ofthese artificial wetlands for the construction ofshelters (predominantly caves) wasparticularly conditioned by the values of theslope (M = 75º; range 47-85º) and the heightof its edges (X = 61,2 cm; rank 19-114 cm), aIn the artificial wetlands of the CGCBA, testsof live capture were carried out usingfact that was also observed in natural areas(Saw of Soriano, 1963). The distances of thedisplacements out of the water (M = 13 m andmaximum values of 108 m) were greater thanthose suggested by other authors (Doncasterand Micol, 1989; Guichón, 2003) and wereperformed with feeding ends. This behaviorcaused numerous patches in the vegetation(mean values of 1.1 m 2 of surface andmaximum of 19 m 2 ) with consequent damagesin the surrounding park (Corriale et al., inpress). As regards population parameters,the indexes of condition (X=5.18; range 4.69-6,63) were relatively high, the same as thedensities (X=3.44 ind. /ha; range 0.5-6.03 ind./ha) that were reached in a relatively shortperiod of time (less than two years). Thevalues of these parameters, along with theproportion of sexes (1:1) and age structuresobserved (6,2% of adults) would also indicateadequate perspectives for population growth(Corriale, 2004). Factors such as the lack ofhigrofile vegetation in masses of water, thepresence of continuous food supplies out ofwater (despite their relatively lower quality),the quiet conditions in the hours of greateractivity of the coypus (Dovecotes et al., 1994),as well as the absence of hunters and ofnatural predators, were considered to fosterthe “plague” behavior of the coypu in this typeof wetlands (Corriale, 2004).The measures of management proposed forthis urban system are based on periodiccampaigns for population reduction and onthe introduction of differential improvements inthe habitat. The aim is, for example, to fosterthe growth of aquatic vegetation in thelagoons, so that the animals can satisfy alltheir life requirements there; as aconsequence, the pastures sown beyond theaquatic vegetation is reduced. Thus, thesemeasures allow a harmonious coexistencebetween human activities and the presence ofthe coypu in this particular type ofenvironment (Corróale et al., 2004).h) Development and test of methodologiesfor capture and chemical immobilization,estimation of age and density.“Tomahawk” trap-cages of 75 x 35 x 35 cm, inorder to test their efficiency, efficacy andselectivity. The concept of “efficiency” was- 7 -
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