Jex-Blake,G. J.

Jex-Blake, G. J.

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NOTES ON POISONING FRUIT BATS (Epimorphu8 wahlbergeiJ.By G. J. JEx-BLAKE,M.n.•Thepassionflowerknownasthe Po'mmed'Or, possiblyPas8ifloralaurifolia, is a creeperproducinga goldenyellowor orangefruit thesizeof a hen'sor goose'segg,that makesverygoodeating. Threeplants of this are trainedup the wire nettinground a lawn tenniscourtin my garden,formingawall 70or 80feetlong,8 or9 feethigh,about2 feetthick, andnineor ten yearsold. During1930and1931wegotmuchfewerpommesd'orfromtheseplantsowingto thedepre-dationsof fruit-eatingbats. In 1930I was lent a bird-catcher'snetto put up roundthe plantsandtrapthe bats; but, for onereasonoranother,noneof the bats allowedthemselvesto be caught-possiblythenetwasill setup, or tooconspicuous.In Augustand September,1931,therewas a goodcropof fruit,but the batsweregettingmostof it, bitinga roundholethe sizeofa shilling--or less-in the upperpart of a pommed'or as it ripenedaud turnedfrom dark bluish greento yellow, and suckingout thecontents. It was thereforedecidedto try andgetrid of the batsbypoisoningthe'mwith strychnine.In orderto accustomthe batsto the ideaof eatingpommesd'ortiedroundwith stringandfastenedto branchesof the creeperinsteadof growingnaturally,a coupleof ripe fruits werethus fastenedonOctober12thin a naturalrecessin the foliage. Next morningthestringwas foundbittenthrough,andthe pommesd'or werelyingonthe groundnearbywith their stalksbittenoff shortandfaint tooth-marksvisibleon their surfaces;it seemedas if the rind of the ripefruit, which certainlyis very hard and elasticunderthe knife, wasmorethanthe batscouldmanageto perforate. After this a coupleoffruits werefixedto the creeperwith wire, and a bit of the rind thesize of a shillingwas cut off at the top of eachto give the bats astart; andthesefruitswereeatenup everynightfromOctober13thto16th. BetweenOctober17thand22nd,eightpommesd'or, eachcon-taining1 grainof strychninehydrochloride,and four containing3grainsof potassiumcyanideeach,werehungup in thecreeper,two anight.Thesewereeatenout completelyeachnight;.a carefulsearchfordeadbatswasmadeall round,but not onecouldbefound,eitherthenor later. It was suggestedto 'meby Mr. Howsethat the alkaloidalsalt strychninehydrochloridemight possiblybe actingas an emetic,so thatthe bats,aftereatingwhatwouldotherwisebe a fataldoseofthe s lt, mightbevomitingit all up beforeit had time to kill~em.On his suggestionthereforethe alkaloidstrychninewassubstitutedfor179its salt the hydrochloride;on October23rd four pommesd'or eachcontaining3l grainsstrychninewerehungup for the bats,andnextmorningthreeof thesewerefound to havebeeneatenout, with agooddealof debrisof rind and fruit on the groundbelow,and theholecut in thefruit verymuchenlarged. The fourthfruit seemedtohaveescapedthebats'notice,but wasfoundeatenouttwodayslater.On October24ththreepommesd'or, eachcontaining7 grainsofstrychninewereput up, andnextdayit wasfoundthat all hadbeeneatenandthat their shellshadbeenbittenout very extensively;thesamething was notedon October26thwhenit was foundthat fourfruits,eachcontaining6 grainsof strychnine,put up thenightbefore,had beeneatenout completely.Two stripedNairobimicewerefound dead besidethe poisoneddebrisof fruit lying on the groundon October24th and 26th, andthese,so far as couldbe ascertained,werethe only victimsof the 59grainsof strychnine,moreor less,eatenwith thelast 11pommesd'orpoisonedand exposed. Meanwhilethe batshad becomenoisierthanusualat night;they aredifficultto seeowingto the numberof treesin thegarden,onedoesnot hearmorethantwo or threesqueakingindifferentdirectionsat any givenmoment,and any estimateof theirnumbersis boundto be mereguesswork, but I assumethat therearea dozenor two in all.Strychninehavingapparentlyfailedasa batpoison,andpotassiumcyanidealso, corrosivesublimate-perchlorideof mercury-was givena trial. On October26thfour pommesd'or, eachcontaining2 grainsof corrosivesublimateandhalf a teaspoonfulof sugarto concealthetasteof thepoison,werewiredto thecreeper. Nextdayit wasfoundthat threeof the fruits werehalf eaten,with someof the contentsdroppedontheground. Four morewereput up,eachwithfourgrainsof corrosivesublimate,andnextday two werefounduntouched,twoaboutone-thirdeaten;a day later no moreof the fruits had beenconsumed.The batsappearedto disliketheir metallicflavour. Thesupplyof pommesd'or having run short, four ripe Cape tomatoes(Cyphomandra betacea)werewiredup in the creeper,but the batsdidnot seemto like themandonly atetwo in thecourseof the nextfourdays. Bats wereheardaboutthe gardeneachnight,andin viewof the apparentfailureof corrosivesublimateas a bat poisonit wasdeterminedto give arsenic trioxide-white arsenic-a trial. OnNovember8th six pommesd'or, eachcontaining10 grainsof whitearsenic,wereput up; nextdayonlytwohadbeentouchedanda littleeaten,thoughelsewhereon the creeperthe naturallygrowingfruitswerestill beingdevoured. By November29 aboutone-thirdof thecontentsof thesesix fruitshadbeeneaten,andtheresthaddriedup;meanwhilethereseemedto be lessdestructionof the ripeningfruitsof the creepergoingon; and it was assumedthat the white arsenichadbeenthemostsuccessfulof thefivebatpoisonstried.1.80During the monthsof December, January, and Februaryverylittlewasheardof batssqueakingroundthehouseat night,but therewasnothingto showwhetherthis was dueto the deathof our bats,or to the fact that the gardencontainedno fruit for themto eat sothat theydidnot continueto visit it.,Tosummarisethe resultsso far obtained,it wouldseemthat anumberof fruit-eatingbats estimatedat a dozenor two, had con-sumed8 grainsof strychninehydrochloride,12 grainsof potassiumcyanide,verynearly59grainsof strychnine,perhaps6 or 7 grainsofcorrosivesublimate,and about20 grainsof white arsenic,betweenOctober17thand November29th, withoutour beingable to find asinglecorpse.Thesearelargequantitiesof verypoisonousubstances.The strychninehydrochloridewouldhavebeenenoughto kill five orsix humanbeings,the potassiumcyanidethreeor four, thestrychnine35 or 40, the corrosivesublimateone, and the white arsenicsix orseven. In the case of wild animals the fatal dosesof solublestrychninenitratequotedby the Germanfirm E. Merck & Co., andsuppliedto meby Mr. Howseareas follows:-Lions: 12 grains. Foxes: i grain.Tigersand leopards:6 grains. Gophers: l' grain.Wolves: 4 grains. Bandicoots:'one-tenthgrain.Dingoes: 5 grains.Thesefiguresshowthatthecarnivoraareeasilypoisonedby relativelyminuteamountsof strychnine,andmanysettlersin this colonyhavefoundstrychninean excellentpoisonfor fruit-eatingbirds. In orderto get further light thrownon the apparentimmunityof our fruit-batsto strychnineandotherpoisons,I wrotetoa friendin London,who forwardedmy letterto Mr. J. N. Ratcliffe,a zoologistwhohasrecentlyspent a coupleof years in tropicalAustraliastudyingthepossibilityof destroyingthe fruit bats that descendin greatflocksand eatout wholeorchardsin that country. Mr. Ratcliffewritesofmy letteras follows:-••Your friend's findingsrather amazedme. Fruit bats are anuisancein the orchardsof New SouthWales,andin certaintropicalfruit plantationsin Queensland. Apart from shooting,the onlyeffectiveactionwhich can be takenis poison. Strychnineis usedas a rule, provingverymuchmoreeffectivethan KON or arsenic. Ihaveheardof morethan a dozenflyingfoxesbeingpoisonedon onepaw-paw,andoversixty in onenighton four appletrees,on whichadozenor so strychninedappleswerehung. Sometimesit seemsasthoughthe merepuncturingof the skin, oncethe poisonhas per-meatedthroughthe pulp, is enoughto finish the bat. With thisexperiencein my mindI haveno answerto yourfriend'sletter. Thebats poisonedin the orchardsvery seldomfly far. In fact theyareusuallyfoundnextmorninghangingon the baitedtree.181••Thata fruitbatcaneatsixgrainsof strychnineandgetawaywith it wouldseemridiculOtl8;butyourfriendis quitedefiniteonthe point. The onlyexplanationwhichsuggestsitselfis that sucha violentoverdoseinducesvomiting.Yet onewouldhaveexpectedthatthis wouldhavebeennoticed-hlldit occurred.I cannotsaywhat wouldbe the orderof the lethal dosejudgingfrom myAustralianexperience.I haveseena manmixa syrupin a saucer,andin it stir groundcrystalsof strychninewhichwouldjust coverthelastquarter-inchof a.,,.pen-knifeblade,andpaintthissyrupoveran apple-andcollectwoOr .threecorpsesnextday,withplentyofsyrupstill leftonthefruit,andin thesaucertooforthatmatter."It is clear,therefOre,that in tropicalAustraliafruit-eatingbatsarereadilykilledby smalldoses-fractionsof a grain-ofstrychnine.Takingall thefactsintoconsiderationmyapparentfailuretokill anybatswith the largequantitiesof poisonconsumedremainsan un-solvedmystery.It:rJ

Notes on poisoning fruit bats (Epimorphus wahlbergerei)

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Notes on poisoning fruit bats

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