Sale,J. B.

Sale, J. B.

Biodiversity Heritage Library OAI Repository

January1960 Page185Procaviidae1. Procavia2. Heterohyrax3. DendrohyraxTHE HYRACOIDEAA Reviewof the SystematicPosition and Biology of the HyraxBy J. B. SALE, B.SC., M.I.BioJ.Biology Department,Royal TechnicalCollegeof East AfricaProbablythe earliestreferenceto theHyraxis that foundin the Bible1whereit is referredto severaltimesby thename'coney'. TodaytheRock Hyraxis stillfoundin partsof theMiddleEastandthreegeneraoccurin Africa. Two of these,Procavia and Heterohyrax, are the well known 'rock rabbits',which live in theshelterof rocky outcropsin many parts of East Africa. The third genusisDendrohyrax,whichis thearborealform livingin forestsandfamousfor its loudcallatnight.Oneinterestingfeatureof theHyraxis itsrelationshiptoothergroupsof animals.Earlierideasemphasisedaffinitieswith thePerissodactyls(horse,rhinoceros)basedon thelackof caninesandthenatureof themolars. This viewis wellexpressedineuvier'sAnimal Kingdom2: "theyare littlelessthanrhinocerosesin miniature."Themodemtendencyis to relatetheHyraxto theelephant.Thegroupingtogetherof thesetwowidelydifferinganimalsis basedonthefactthatthefossilHyraxof theEoceneperiodhavea numberof characteristicsin commonwiththeancestorsof themodemelephant.Arisingfromthesamegroup,veryearlyin thePalaeocene,aretheSirenia,or seacows,ofwhichtheDugongisanexamplefoundonEastAfricancoasts.Togetherwiththeirfossilancestors,theHyrax,elephantsandseacowsareincludedby mostmodemtaxonomistsin thePaenungulata3or 'near-ungulates'.Primitiveungulatefeatureshownby thegroupincludeseveraldigitswithpoorlydevelopedhoofs;incisorsandcaninesreducedtosinglepairsoflargetusksandmolarsspecialisedforgrindingwiththedevelopmentofcross-ridges.Thefailureof thetestestodescendinto a scrotumin all livingPaenungulatesi a curiousfeaturewhichseemsto lackanadequatefunctionalexplanation.Wemaysummarisetheclassificationof livingPaenungulatesa follows;-CLASS: MAMMALIASuperorder: PaenungulataOrder 1. Hyracoidea Family:GenusOrder 2. ProboscideaOrder 3. SireniaFamily: ElephantidaeGenus 1. Loxodonta-African Elephant2. Elephas-Indian ElephantFamily: 1. TrichechidaeGenus:Family: 2.Genus:Family 3.Genus:Trichechus-manateeof Atlantic OceanDugongidaeDugongRhytinidaeRhytina1 Lev. 11.5;Ps. 104.18;Prov. 30.26.I The Animal Kingdom. Cuvier 1884,pp. 120.8 Simpson,G. G. 1945. The Principlesof Classificationand a Classificationof theMammals.Bull. Amer.Mus. Nat. Hist. 85.Page186 TheHyracoidea Vol. XXIll. No.5 (102)Thefirsttwo generaof theHyracoidea,Procavia and Heterohyrax,havemuchin common. Not only aretheirhabitsalmostidentical,but theyshowveryfewanatomicaldifferenceson whichto basea divisionintoseparategenera.Themaindistinguishingfeaturesmaybelistedthus:Feature ProcaviaIHeterohyrax(a) Hairs surroundingdorsalwhite orglandularspotblackchestnut(b) Molar teethbroadtend o benarrowerthanProcaviaI(c)Upper incisorsIverys rong: weakerthanI closeProcavia:togetherwider apartIn addition,thereareslightdifferencesin themeasurementsof somefeaturesof theskull. Apart fromthecolourof thehairsof thedorsalglandularspot,it isverydifficultto stateto whichgenusa givenspecimenbelongsunlessonehasanidentifiedspecimenfor comparison.Thequestionastowhethertwoseparategeneraarejustifiedseemsto arise. Someideaof theconfusionis gainedwhenonenotesthat Allen (1939)4placesHeterohyrax we/witschiias a subspeciesof Procaviacapensis. SomeauthoritiesregardHeterohyraxasa sub-genusof Procavia5• Therearesomeothercasesofconfusionin thenamingof subspeciesandathoroughrevisionof thesetwogenera ppearsto benecessary.TheTreeHyrax(Dendrohyrax)is readilydistinguishablefromtheRockHyraxesbothby its arborealandnocturnalhabitsandon anatomicalgrounds. The longsofthairisquitedifferentfromtheshorterhairof theothertwogenera.Themuzzleis longerand the teethshowconsiderabledifferences.For instance,the outerpairof lowerincisorsretainthetricuspidconditionin theadult,whilstthis is lostin theadultsof ProcaviaandHeterohyrax.Thehabitsof theRockHyraxesarebetterknownthanarethoseof theirnocturnalrelative,theTreeHyrax. The rockyshelterswheretheseanimalslive in coloniesoffiftyormoreareoftenlocatedindryaridareas. A colonyin theSaharawasnotedby an explorerin an areawhich was completelywaterless6•The urineis oftenviscousandthekidneymustremovea largeamountof thewaterfromit, thuscon-servingwaterin the body. The habit of urinatingand defaecatingin the samespotis characteristicof theRockHyrax. A studyof theoccurrenceof thishabitintheanimalkingdomdoesnotseemto providea readyexplanationof itsusefulness.Thewhiterhinocerosis anothernotedexampleof ananimalwhichhasa communaldungheap. Feedinggenerallytakesplaceduringthedaytime,theearly morningandlateafternoonbeingtimesof maximumactivityoutsidetherockyholesin whichthenightandmuchof themiddleof thedayarespent.TheHyraxis,of course,a herbivoreandthedietincludesleaves,fruitsandmanyvarietiesof grasses.Also lichenshavebeenreportedas food,particularlyin areaswhere,duetolackof rainfall,otherformsof vegetationarescarce. In factit appearsthatatsuchtimesHyraxwilleatalmostanyvegetablematerialavailable,andextremely, Allen 1939. Checklistof African Mammals. Bull. Mus. CompoZool. LXXXIII.5 Seefor instanceAnimauxProtegesau Congo Beige. 1953. InstitutdesParesNationauxduCongoBeige,pp. 66., TraitedeZoologie. TomeXVII, pp. 892.January 1960 TheHyracoidea Page187GEOGRAPHICAL DISTRIBUTION OF GENERA INAFRICAPROCAYIA,,~ HETEROHYRAX"~ DENDROHYRAX.RedrawnafterTraitedeZo%gie.•.s.TheHyracoidea Vol.XXIII. No.5 (102)dryandunappetisingstalksandgrassescanbefoundamongthestomachcontents.Thesightof theHyraxis keenin spiteof thefactthatit spendsmuchof its timein completedarknessandvisionof objectsasmuchasamileawayhasbeenreported.Whenlyingoutin thesun,astheyoftendo duringthemiddleof theday,theyhavethehabitof gazingup directlyat thesun. This hasledto thebeliefamongsomeAfricantribesthattheHyraxareblind. It is reported7that theeyeof theHyraxdiffersinstructurefromthatof otheranimals.Hearing,likesight,is probablyquitekeenandageneralalertnessi supplementedbyadistinctivewarningcryontheapproachof anenemy. At suchtimeonecanseemembersof thecolonyhurryingbackto theirholes,negotiatingthesteepfacesofrockswith superbagility. The thick flat solesof thefeet,whichareclammyinlife, arewelladaptedto thismodeof life, althoughtheydo not possessany realsuctionalpower. Someobserverstatethat the Hyrax breedsoncea yearbutwhetherthereis a definitebreedingseasonis not clear. Two or threeyoungarebornperlitterandthegestationperiodis saidtobesevenandahalfmonths.Little hasbeenrecordedof sociallife within the Hyrax colony. Gregariousanimalslivingin a colonyof thiskindalwayshavea fairlyintricatesocialstructure.The oldermalesare saidto remainon guardoutsidetheentrancesas 'sentinels'andsomeclaimthatadultmemberstrainupthejuvenilesin thewaysof thecolony.No real evidenceseemsavailableto supportthis, however. Fighting,probablybetweenmales,is sometimesnoticedbut whetherthis has any definitesocialsignificanceis notknown.Themodeof lifeof theTreeHyraxisverydifferentfromthatof theRockHyraxes.Theyaresolitaryanimals,hidingin hollowsandin thebranchesof treesduringthedayandbecomingveryactiveat nightwhentheydescendto thegroundin searchof food. Thecryis of muchgreatervolumethanthatof theotherhyraxesandis anuisanceto thewould-besleeperin someforestareas. Only one or two youngarebornata time.The Hyracoideahavereceivedverylittleattentioneitherfromthenaturalistorfromtheseriousscientificresearchworker. Theliteratureonthisgroupof animalsis probablymoreslenderthan that of any othermammalianorder. Therearemanyproblems,suchas the natureof thesocialstructureof the Hyrax colony,remainingto be investigated,Indeed,all aspectsof thebiologyof theseanimalsshouldprovidea rewardingfieldof research.A Snake's MealDuringa recentfieldcoursewewerebroughta maturespecimenof thecommonhousesnake(Boaedonfuliginosusfuliginosus. Boie.). On examiningthespecimento ascertainthecauseof death,we foundthata rat thathad recentlybeencon-sumedbythesnake,hadeatenitswaythroughtheoesophagusandthelateralbodywall. Bothanimalshadbeenfounddeadasa result.Malcolm J. Coe7 Austin Roberts. The Mammalsof SouthAfrica. 1951,pp. 252.

The Hyracoidea

http://www.biodiversitylibrary.org/content/part/EANHS/XXIII_No.5_102__185_1960_Sale.pdf

The Hyracoidea

Abstract

Similar works

Full text

Available Versions

Biodiversity Heritage Library OAI Repository