I l l i n o i s Frogs & Toads - Welcome to Illinois DNR · F Frogs and toads are not shown in equal...
Transcript of I l l i n o i s Frogs & Toads - Welcome to Illinois DNR · F Frogs and toads are not shown in equal...
PhotographsbyMichaelRedmer©. Frogsandtoadsarenotshowninequalproportiontoactualsize.
F rogs and toads are the most conspicuous members of a very
secretivegroupofanimalscalledamphibians.Frogsandtoadsare
wellknownfortheirmatingcallandlong,insect-catchingtongue.
They are excellent gauges of environmental health because of their close
contactwithaquatic,wetland,andterrestrial*environments.Theyhavemoist,
sensitive skin that allows chemicals in the environment topass into their
bodies.Furthermore,theireggslackahardshellsotheirdevelopingyoung
also aredirectly exposed to the environment.Thepuzzlingdisappearance
of some frog and toad species in remote, pristine parts of the world has
scientists concerned about overall planetaryhealth.
*see glossary
1. woodfrog, Rana sylvatica 2. northernleopardfrog,Rana pipiens 3. chorusfrogcomplex,Pseudacris triseriata-maculata* 4. Fowler’stoad,Bufo fowleri 5. greentreefrog,Hyla cinerea 6. greenfrog,Rana clamitans 7. springpeeper,Pseudacris crucifer 8. graytreefrogcomplex,Hyla chrysoscelis-versicolor* 9. cricketfrog,Acris crepitans10. southernleopardfrog,Rana sphenocephala11. Americantoad,Bufo americanus12. plainsleopardfrog,Rana blairi13. bullfrog,Rana catesbeiana14. easternspadefoot,Scaphiopus holbrookii15. easternnarrowmouthtoad,Gastrophryne carolinensis16. Illinoischorusfrog,Pseudacris streckeri illinoensis17. bird-voicedtreefrog,Hyla avivoca18. crawfishfrog,Rana areolata19. pickerelfrog,Rana palustris20. uplandchorusfrog,Pseudacris feriarum
This poster was made possible by:
Illinois Department of Natural Resources
Division of Education
Illinois Natural History Survey
Illinois State Museum
Illinois Department of Transportation
Text: Christopher Phillips (Illinois Natural History Survey)
Design: Illinois State Museum
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I l l i n o i s
Frogs & Toads
Key
* Both the western chorus frog, Pseudacris triseriata, and the boreal chorus frog, Pseudacris maculata, are found in Illinois. They are difficult to distinguish by their appearance, so they are represented by one image on this poster. The eastern gray treefrog, Hyla versicolor, and Cope’s gray treefrog, Hyla chrysoscelis, also are similar in appearance and are represented by one image.
Anatomy
Illustration from Smith, 1961
F rogsandtoadsaretheonlymembersofthePhylumChordata,ClassAmphibia,andOrderAnura.
Unliketadpoles,adultsdonothaveatail.Adultfrogsandtoadshaveasquatpostureandstrongrearlegs,
whichgivethemtheabilitytojumplongdistances.Theirlong,retractabletongueisusedtocatchtheir
mainfooditem,insects.
Thetympanicmembrane,ortympanum,aidstheprocessofhearing.Thiscircularstructure,locatedon
eachsideoftheheadbehindtheeyes,picksupvibrationsinairorwaterandpassesthemtotheinnerear.
Frogsandtoadsbreathethroughtheirlungslikemostterrestrialvertebrates,buttheyalsoutilizetheirsoft,
moistskinasasecondarymeansoftakinginoxygen.Thistypeofbreathingrequiresthattheskinbeboth
moistandpermeable.Theirskinremainspermeablebecausetheydonothaveaprotectivecoveringlikescales,
hair,orfeathers.Theymaintainmoisturethroughmucousglandsecretionsandbystayingnearwater.Toads
haveasomewhatmorewatertightskinthanfrogsandcanthereforeventurefartherfromwater.
Toadsarealsocharacterizedbythehornybumps,sometimescalledwarts,ontheirskin.Themostpro-
nouncedofthesebumps,calledparotoidglands,arefoundjustbehindthetoad’seyesandproduceapoison
thathelpsindefenseagainstpredators.Thepoisonrepelsanimalsaslargeasraccoonsbecauseofthemild
mouthdiscomforttheyexperiencewhentryingtoeatatoad.Oftentheydropthetoad,allowingitsescape.
Life History
Illustrations by Mark Sabaj, Illinois Natural History Survey
A ll Illinois frogs and toads have a complex, biphasic life cycle. Adults are aquatic, semi-aquatic, or
terrestrial,butallspecieslaytheireggsinwater.Duringthebreedingseason,whichmaystartasearlyas
FebruaryinIllinois,malescongregateatwetlandsandbeginchorusing.Themales’callsattractfemales
tothewetlands,andsoonmalesandfemalesarepairedinamplexus(1).Amplexusendswithfertilization:the
femaleexpelshereggsintothewater,andthemaleimmediatelycoversthemwithsperm.
Agelatinouscoatingusuallycoversanuraneggs(2),whichmaybelaidsingly,insheets,strings,orglobs,
dependingonthespecies.Somespecies’eggsareattachedtosticksorleaves;otherssimplyfloatfreelyinthe
water.Fertilizedeggsdevelopandhatchintofree-swimminglarvae,ortadpoles(3&4),withinafewdays.
Tadpoleshaveahorny,beaklikemouthdesignedforscrapingalgae,andtheybeginfeedingalmostimmedi-
atelyafterhatching.Afewweekslater,hindlimbsappear(5),andwithinamonthortwothetadpoleshave
undergonemetamorphosis.Exceptforatemporarytailstub,thenewlytransformedfrogletslookmuchlike
theadults.Theyusuallyleavethewaterandtakeupexistenceonlanduntilcoldweatherpromptsthemto
seekoutasafeplace,suchasthemuddybottomofapond,forhibernation.
Althoughthelarvaeareherbivorous,alladultfrogsandtoadsinIllinoisarecarnivorous.Themostcom-
monfooditemsareflyinginsects,suchasfliesandmosquitoes.Althoughadultsareprimarilynocturnal,they
maybeseenorheardduringtheday,especiallyiftheweatherisovercastorrainy.
Bibliography Agency ResourcesTheIllinoisDepartmentofNaturalResources(IDNR)offersavarietyofinformation
aboutfrogsandtoads.TheDivisionofFisheriesResourcesregulatestheharvestoffrogsfor
gamepurposes.TheIllinoisNaturalHistorySurveystudiesfrogandtoaddistributionsand
populationlevelsandmaintainsaresearchcollectionofanurans.TheIDNRDivisionof
Educationprovidesaquatic-relatededucationalmaterialsforteachers,includingtheAquatic
IllinoisandBiodiversity of Illinois,Volume I: Aquatic HabitatsCD-ROMs.Wetlandkitsfromthe
EducationSectionoftheIllinoisStateMuseumareavailableforloanatlocationsstatewide.
Illinois Department of Natural Resources
Illinois Natural History Survey1816SouthOakStreet
Champaign,IL61820
217-333-6880
http://www.inhs.uiuc.edu
Illinois State MuseumEducationSection
502SouthSpringStreet
Springfield,IL62706-5000
217-782-5993
http://museum.state.il.us
Division of EducationOneNaturalResourcesWay
Springfield,IL62702-1271
217-524-4126
http://dnr.state.il.us
Division of Fisheries ResourcesOneNaturalResourcesWay
Springfield,IL62702-1271
217-782-6424
http://dnr.state.il.us
Glossary
Amplexus thematingclaspoffrogsandtoads;themaleholdsthefemalefrombehindwithhisforelegsfirmlyaroundherchest
Anuran memberofthevertebrateorderAnura,characterizedbylackofatail,moistskin,andlonghindlegsadaptedforleaping:afrogortoad
Biphasic twodistinctphases;usuallyreferstoalifecyclethathasalandandawaterportion
Carnivorous havingadietthatincludesmainlyanimals
Dorsolateral Fold alineofraisedskinalongeachsideoftheback(seeAnatomyillustration)
Endocrine ductlessglandsandtheirregulatoryproducts
Heavy Metals potentiallypoisonousmetalssuchaslead,mercury,andcadmium
Herbivorous havingadietthatincludesmainlyplants
Larva (pl.larvae)thenewlyhatched,immatureformofananimalthatun-dergoesmetamorphosis,differingmarkedlyinformandappearancefromtheadult
Metamorphosis amarkedchangeintheformorstructureofananimaloccurringafterbirthorhatching
Mucous Gland Secretion clearwateryliquidthatissecretedontotheskinofamphibiansthroughsmallporesdistributedoverthebodysurface
Nocturnal activeprimarilyatnight
Parotoid Glands paired,wartlikeglandsintheskinoftoads;locatedbehindtheeyesorintheneckandshoulders
Snout-to-Vent Length thedistancefromthetipofthesnouttotheexcretoryopening;thestandardmeasurementforfrogsandtoads
Terrestrial landbased,orlivingonland
Tympanum (tympanicmembrane)theexternallyvisiblepartoftheeardruminmostfrogsandtoads(seeAnatomyillustration)
Vertebrate animalwithabackbone
Frog & Toad Facts Frogsandtoadsdonotcausewarts.
ThelargestIllinoisanuranisthebullfrog,Rana catesbeiana,whichcanattainasnout-to-ventlengthof15cm(6inches).
ThesmallestIllinoisanuranisthecricketfrog,Acris crepitans,whichaverages2cm(1inch)snout-to-ventlength.
Theaveragefrogcanleapadistanceequaltotentimesitsbodylength.
Mostburrowingfrogsdigwiththeirhindlegs,buttheIllinoischorusfrog,Pseudacris streckeri illinoensis,isoneofonlyafewburrowingspeciesthatdigswithitsfrontlegs.
Thedietoftheeasternnarrowmouthtoad,Gastrophryne carolinensis,consistsalmostexclusivelyofants.
Thelongtongueoffrogsandtoadsisfoldedinhalfwhenstoredinthemouth.Whenextendedforcapturingprey,thetongueunfoldsandis“flipped”outratherthanbeingcastoutstraight.
TheIllinoischorusfrog,Pseudacris streckeri illinoensis,canhuntforfoodwhileitisunderground.Itprobablyeatsavarietyofinsectlarvae,suchascutworms(mothlarvae),thatitfindsinitssandyburrows.
Bullfrogs,Rana catesbeiana,arefamousfortheirincredibleeatinghabits.Theywillattempttoeatanythingthatmoves—thattheycanatleastpartiallyswallow.Theyhavebeenknowntoeatbabyducks,smallmammals,otherbullfrogs,andsnakes.
ThetreefrogsofIllinoishaveastickycupattheendofeachtoethatallowsthemtoclimbverticalsurfacessuchaswindowsandtreetrunks.Treefrogsmaybefoundinbranchesmorethanfiftyfeetofftheground.
Afemalebullfrog,Rana catesbeiana,canlayover20,000eggsinathinfilmmeasuringtwofeetbytwofeet.
SomeIllinoisfrogs,suchasthewoodfrog,Rana sylvatica,accumulateglycerolintheirbodytissues.Theglycerolactsasanantifreeze,allowingthemtosurvivesubfreezingtemperatures.
Frog CallsAnimalsproducesoundsforavarietyofreasons,
but the primary function of vocalization is
announcing the presence of one individual
toothersof the same species.Frogs and toadshave
well-developedvoicesthatareusedtoattractmates,
proclaimfeedingterritories,andsignalalarm.Ofthese
functions,thematingcallsofthemalesareprobably
themostfamiliartous.Justasinbirds,eachspecies
offrogortoadhasauniquematingsong,andbiolo-
gistscanidentifyanindividualspeciesbyitscallalone.
Anuransproducesoundsinamannersimilartothat
ofmostothervertebrates,bypassingairoverthevocal
cords.Frogsandtoadstaketheprocessastepfurtherby
usingthevocalsac—looseskinusuallylocatedunder
thelowerjaw—toresonateoramplifythesound.Both
malesandfemalespossessfunctionalvocalcords,but
theyarebetterdevelopedinmales.Onlymaleshave
vocalsacs,whichaccountsforthedifferenceinsound
productionbetweenthesexes.
Frog calls can be “described” in scientific terms
byplayingarecordingofacallthroughanelectronic
sound analyzer.The resulting graph, called a sono-
gram,isavisualrepresentationofthecall.Scientists
usesonogramstoidentifyspecieswhosecallscannot
bedistinguishedwiththehumanear.Forthisreason,
sonogramsareusedtodistinguishbetweenthetwospeciesofgraytreefrogthatoccurinIllinois.Theeastern
graytreefrog,Hyla versicolor,andCope’sgraytreefrog,Hyla chrysoscelis,areidenticalinoutwardappearance
andwereconsideredtobeofthesamespeciesuntilbiologistsdetecteddifferencesintheirmatingcalls.So-
nogramsofthetwomatingcallsshowthatthecallofCope’sgraytreefroghasahigherpitchandmorepulses
persecondthanthatoftheeasterngraytreefrog.However,thedifferencesthatappearobviousinthesound
analysisareactuallyverysubtleinnatureandcanbepickeduponlybyatrainedear.
I l l i n o i s
Frogs&
Toads
Behler,J.L.,andF.W.King.1979.The Audubon Society field guide to North American reptiles and amphibians.AlfredA.Knopf,NewYork.719pp.
Conant,R.,andJ.T.Collins.1991.Reptiles and amphibians of eastern/central North America.HoughtonMifflinCompany,Boston.450pp.
Dickerson,M.C.1907.The frog book: North American toads and frogs with a study of the habits and life histories of those of the northeastern United States.Doubleday,PageandCo.,NewYork.253pp.
Duellman,W.E.,andL.Treub.1986. Biology of amphibians.McGraw-Hill,Inc.,NewYork.670pp.
Halliday,T.,andK.Adler(editors).1986.The encyclopedia of reptiles and amphibians.FactsonFileInc.,NewYork.143pp.
Herkert,J.R.,editor.1992.Endangered and threatened species of Illinois: Status and distribution.Vol.2,Animals.IllinoisEndangeredSpeciesProtectionBoard,Springfield.142pp.
Johnson,T.R.2000.The amphibians and reptiles of Missouri.DepartmentofConservation,JeffersonCity,Missouri.400pp.
Parmalee,P.A.1954. Amphibians of Illinois.StoryofIllinois,no.10.IllinoisStateMuseum,Springfield.38pp.
Phillips,C.A.,R.A.Brandon,andE.O.Moll.1999.Field guide to amphibians and reptiles of Illinois.IllinoisDepartmentofNaturalResources,IllinoisNaturalHistorySurvey,Champaign,Illinois.Manual8.282pp.
Smith,P.W.1961.The amphibians and reptiles of Illinois.IllinoisNaturalHistorySurveyBulletin 28:1298.
Vogt,R.C.1981.Natural history of the amphibians and reptiles of Wisconsin.TheMilwaukeePublicMuseum,Milwaukee.205pp.
Wright,A.H.,andA.A.Wright.1949.Handbook of frogs and toads.ComstockPublishingCo.,Ithaca,NewYork.640pp.
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The vertical axis (y) represents the pitch, and the horizontal
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Conservation
Cricket frog (Acris crepitans), from Slime, Scales and Mudpuppy Tails, 1997,
Illinois Department of Natural Resources, Office of Public Services, Division
of Education, Springfield
O verthelastfewyearstherehasbeenincreasedconcernaboutworldwidepopulationdeclines
andevenextinctionsoffrogandtoadspecies.Habitatdestructionanddegradationareclearly
responsibleinsomecases,butthemostalarmingdeclineshaveoccurredinrelativelypristine
environmentssuchastherainforestsofeasternAustraliaandthecloudforestsofCostaRica.Closerto
home,biologistsintheupperMidwesthavebeennoticingthedisappearanceofoursmallestfrog,the
cricketfrog(Acris crepitans).Untiltheearly1980s,cricketfrogswereamongthemostcommonanurans
inIllinois,andtheycouldbefoundinalmosteverycounty.Recently,biologistshavenoticedadeclinein
thenumberofcricketfrogpopulationsintheChicagoregionbutnotdownstate.Amongthecausesthat
havebeensuggestedforthisdeclineisbuild-upoftoxicsubstances(pesticides,heavymetals)inthefrogs’
breedingponds,leadingtoendocrinedisruption.AsurveyofmuseumspecimenscollectedinIllinoisover
thepast100yearsshowedthatmorefrogsfromtheChicagoregiondisplayedanatomicalsignsofendocrine
disruptioncomparedtotherestofthestate.IntheheavilyindustrialandurbanlandscapeoftheChicago
region,habitatdestructionandfragmentationarealsolikelyinvolved.
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Printed by the Authority of the State of Illinois IISG 08-674 10M 03/08
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