MISCELLANEOUS PUBLICATIONS MUSEUM OF ZOOLOGY, UNIVERSITY OF MICHIGAN, NO. 132
The Life and Demography of the Side-Blotched Lizard, Uta stansburiana
BY DONALD W. TINKLE Museum of Zoology, University of Michigan
ANN ARBOR MUSEUM OF ZOOLOGY, UNIVERSITY OF MICHIGAN OCTORER10, 1967 MISCELLANEOUS PUBLICATIONS MUSEUM OF ZOOLOGY, UNIVERSITY OF MICHIGAN
The publications of the Museum of Zoology, University of Michigan, consist of two series-the Occasional Papers and the Miscellaneous Publications. Both series were founded by Dr. Bryant Walker, Mr. Bradshaw H. Swales, and Dr. W. W. Newcomb. The Occasional Papers, publication of which was begun in 1913, serve as a medium for original studies based principally upon the collections in the Museum. They are issued separately. When a sufficient number of pages has been printed to make a volume, a title page, table of contents, and an index are supplied to libraries and indi- viduals on the mailing list for the series. The Miscellaneous Publications, which include papers on Geld and museum techniques, monographic studies, and other contributions not within the scope of the Occasional Papers, are published separately. It is not intended that they be grouped into volumes. Each number has a title page and, when necessary, a table of contents. A complete list of publications on Birds, Fishes, Insects, Mammals, Mollusks, and Reptiles and Amphibians is available. Address nnquiries to the Director, Museum of Zoology, Ann Arbor, Michigan.
LISTOF MISCELLANEOUSPUBLICATIONS ON REPTILES AND AMPHIBIANS No. The amphibians and reptiles of the Sierra Nevada de Santa Marta, Colom- bia. By ALEXANDERG. RUTHVEN. (1922) 69 pp., 12 pls., 2 figs., 1 map ... $1.00 No. A contribution to a knowledge of the herpetology of a portion of the Savanna Region of Central Peten, Guatemala. By L. C. STUART.(1935) 56 pp., 4 pls., 1 fig., 1 map ...... $0.50 No. A contribution to the herpetology of the Isthmus of Tehuantepec. IV. An annotated list of the amphibians and reptiles collected on the Pacific slope during the summer of 1936. By NORMANHARTWEG AND JAMESA. OLIVER.(1940) 31 pp...... $0.35 No. Studies of Neotropical Colubrinae. VIII. A revision of the genus Dryado- Phis Stuart. 1939. By L. C. STUART.(1941) 106 pp., 4 pls., 13 figs., 4 maps ...... $1.15 No. A contribution to the knowledge of variation in OPheodrys vernalis (Harlan), with the description of a new subspecies. By ARNOLDB. GROB- MAN. (1941) 38 Pp., 2 figs., 1 map ...... $0.35 No. Taxonomic and geographic comments on Guatemalan salamanders of the genus Oedipus. By L. C. STUART.(1943) 33 pp., 2 pls., 1 map .... $0.35 No. Home range, homing behavior, and migration in turtles. By FREDR. CAGLE.(1944) 34 pp., 2 pls., 4 figs., 1 map ...... $0.35 No. The amphibians and reptiles of Alta Verapaz, Guatemala. By L. C. STUART.(1948) 109 pp., 10 figs., 1 map ...... $1.50 No. Studies of the black swamp snake, Seminatrix pygaea (Cope), with des- criptions of two new subspecies. By HERNDONG. DOWLING.(1950) 38 pp., 6 figs., 1 map ...... $1.25 No. A brief review of the Guatemalan lizards of the genus Anolis. By L. C. STUART.)1953( 31 pp...... $0.50 No. The anatomy of the head of Ctenosaura pectinata (Iguanidae). By THOMASM. OELRICH.(1956) 122 PP., 59 figs...... $1.85 No. The frogs of the hylid genus Phynohyas Fitzinger, 1843. By WILLIAME. DUELLMAN.(1956) 47 pp., 6 pls., 10 figs., 4 maps ...... $0.70 No. Variation and relative growth in the plastral scutes of the turtle Kinoster- non integrum Leconte. By JAMESE. MOSIMANN.(1956) 43 pp., 1 pl., 24 figs...... $0.75 (continued on inside back cover) MISCELLANEOUS PUELICATIONS k1USEUhI 01: ZOOLOGY, UNlVEKSlTY OF MICHIGAN, NO. 132
The Life and Demography of the Side-Blotched Lizard, Uta stansburiana I !\KC :I( bl:~Ic~l-iryill Llt;15 . . 4fi (;IO\VIIIill L\:cigIr~ 117 1!1:1s ~l!l (;towll~of 1I1c 'I'ail ill Illas ... 5:i I Silr ;llrtl Age SL1.1lclul.c in Ill(. ~'0l)u~;llioll.;...... I nci ~'ol)rll;llioll ~)c.~rsiry,I(~OIII;ISS, ;l~ld RC.~III;IL~OIIS 01 NIIIII~)(.I~ . . I -I :i F.ll'c.cls of Radi;~tio~r011 llrc 1'ol)ulalioll ...... 148 (:o~~~l~al-alivcI)CIIIO~I.;I~)~I~ of I ...... 151 I'ol)~~l;~tio~~1)).11a111its of (:olol;ltlo I.i~al-(IS...... l (i3 JLLUSTRATIOKS PI.A'Tl? PAGE I . Texas study area ...... 9 11 . Young fet~ialeand niale utas ...... 35 111 . Adult feniale and liiale utas ...... 36 I' Atlult female and niale uta from Colorado ...... 153 FICURE 1 . Sequence of toc nutnbering ...... 12 2 . Insignia used for individual recognition ...... 13 5 . Tiiiie of appearance of hatclilings ...... 3-1 4 . Correlation of weight with snout-vent lengt11 ...... 51 5 . Correlation of weight with age ...... 52 6 . I.engl11 of tail plotted against snout-\en1 length ...... 94 7 . Periotlicity of utas ...... 89 8. FIonlc range size of fcmales ...... 95 . Ho~nerange size of males ...... 96 10. hIean tcn~peraturesof cloaca, substrate, ant1 air ...... 111 I I . Air ~cnlperaturesin unshatletl pol.tion of study area ...... 115 12 . Teniperat~uesat surface in sllaile of yuccas and 6 inches beneath surface .....116 13. Tcnll)eratures in sun and in sliarlc of mesquite ...... 117 14 . Air teniperature ant1 tcmpcratu~.c1 inch below surface ...... 118 15 . Air tcliil. erature above ground ant1 in artilicial burrow ...... 119 16. ;\ir Lc.ml>erature above ground and inside packrat nest ...... 120 17 . S~trvivorsliipcurve for n~aleand female utas ...... 129 18. Age stl.ucture of nialcs in uta ~)opulation...... 138 19 . .4 ge slr~lctureof fen~alcsin uta populatiotl ...... 139 20 . Size groups of Colorado utas ...... 158 I)I,;.I.AII.I,:I)STIJI)II,S 01' II;ILIII.;I~ ~)ol~l~l:ttions,~);trticr~I;trly of reptiles, :]I-e 1-arc. Such stutlics are esse11ti;rl to tlisclose wIi;tt ecologic.al elifI'erenccs exist ;rt the intlivicllral ;rnd 11op~1l;itionlevel ill response to tl~ecnvil-onnlental conditions 1)rcv;tiling in the ;trc:r ol' str~tly.7'lrese tlilTc~.cnces;II-e generally quantitative and, ;lt least for this rc;rso11, pol~ul;ttior~stlrclies muat be quantitative. It is not sl~lIic.ient,;tntl ~)c~.lr;tl)s1101 sisnilic.:r~~t,to know tl~cfor~n of ;I grolvtll c-urvc Sor single inclivitl~t:tls or to know its lo~lgevity.7'1~ avcragc rate ol' growl11 ol' a large s;tml)lc ol' ;I loc.;tl pol)rrl;ttion ;t~~tlthe lil'c exl)ect;tncy of its r11cnlbe1.s are of g~.c;ttc~.interest. A4ost strtclies ol' life Ilisto~.iess11Kc1- l'1.om ;I 1;tc.k ol' clr~;tntitativerestrlts; tl~isl';1111t exists in sonre ;tsl)cc-ts ol' thi:, str~tly.(:onscc]rlcntly, nie;rningfrtl c.ornp;r~-isons01' tlillc~.c~ltsl)cc-ics or ol' tlilTcrcnt ~)ol)ul;ttionsof the s;tlne spccic:, cxnnot be 111;ttlc. I)cc-;t~~sethe cc.ologic.:rl p;tl.;llrretcl-s of tlre lml~~latio~is :u-c inexactly known. '1-l~epriticip;tl aim or this stntly has been to q\r;i~ltiCy ;IS many ;tsl)ec-ts 01' the lil'c 1iisto1.yof tllc sitlc-blotclietl liz;r~.tlas l)ossihlc. i\l~;t~-t1'1-om the ilnl)o~.t;t~ic.col' sr1c.11 ;I dcsc~.il)tivcstl~tly of the it11 tecology or ;I sl)ccics, it shortltl ;11so gclicl-;rtr tesla1,lc ~)~.e(lit.tionsconterning tllc tlc~nogl-;tl)hyof the s;tmc spcc.ies in tlillel-cnt j);tl'ts ol' its I-;III~~.The str~tly sho~rltlst~ggcsi I;tl~o~-:t~o~-y ;tntl licltl exl)erinrcl~tsth;tt m;ty l)c of mol-c impel-- 1;rnc.c in ;rnslvering sl)cc.ific. cjuestions tlian is j>o.sl fnc.10 tlescriptive ecology. I?in;tlly, c1tr;tn tit;rtivc clat:r may I,e ~~sel'rtlto tliosc i11tc1-cstce1in tl~ctheoretic-;t1 :tsl)t~ctwol'~jolx~l:~tion cc ology i111t1 01' ~~ri(.~-oc\'olr~tio~~.1 e;in (lo 110 I)etter than to lja~-;~l)h~-nscthc st;tterncnt of Cole (1!)5,1) tha~s11cI1 things ;IS birth I.;rtc, tlc;ttIi I.;I~c,and the ;tgc conll)oaition of a po~~rrl;ttion;IS well as its ability to ~,clwotlucewcl-c conseqttenccs of the life history features of the int1ivitlu:tl org;tiiism. N;rtrrral selection will 1)e inlluenti;tl in sh;tl~irlglire history patterns to c.orrcsl,ontl to elficicnt l)ol)~~l;ttions.Coml~;t~-;rtive sttrtlies of lile history ;I~)~)c;II-to be fully ;IS n~c:tuingl'~rlas stutlics of cornl);rr;rtivc morphology, corn- I);II';II~\JC l)syc.liology, 01. co~nl):t~-;rti\.cphysiology, I~lrtIi;tvc heen ncglec.tetl Iron) tllc evo1ution;try poin~of I11elv. ' I'lle I)l-csent st~rtly1i;tcl its inccl)tion in 1!)57, 11r1t ilrtenai1.e field st~ttlics wc.1.c I~cgrrnin I!)(iO ;ulcl conti~~uetltllrough l!)(if. Dr~ringtltis pel-iotl I con- tlt~ctctlnumerous exl)crin~entsin the f~eltl:tnd labor;ttol.y, but tlre ~najority ol' tllc information has come l'rom 9729 1i~;trtls1n2t1-kctl in the fieltl, TI-oln wl~ic.11 we have ol)t;~inetlI2,!)27 c.:tptures. Scveral thousand adclitional lizartls 11;tvc been collectetl 1'01-stlttlies 1,anging from the determination of clutch six to exlxxinlents ~\ritll the extrinsic: r;~cto~-s1-esponsible for initiating estro~ls.'Ihc 1.cs~11tshave I)eeu 21 fairly cornplcte knowledge of the biology of this specics. 'I'll~.oughot~ttile ensrling tlisc~lssionsI 11a\.c tl~-:~wnhea\.ily from my own previot~s~)~~blic;ttions ;tntl tllose ol Iny stt~tlents.lkcal~se I have been ;tided in this ~.csc;rrtl~Ijy a 1;11,gcnr~ml,c~- ol stltclents, it Ilas becoinc tlillic.ult for me to clistinguisli their itle;~sI'I.OII~ my own. I tr~~stit 5vill be clear to c;tch of tllem where srlc.11 has been the c,;tsc ant1 tli;tt tllc); will accept crctlit for the idea ;und lo~gi\c my 11si11 pation ol it. rI'~\xo~o~~(:KEI.~\TI~I\'SIIII~S 01; IJln.-'l'lic gcntls Utcr contains perhaps ;r Ilal1' tlo~c.11gcnel-;dly recog~li/etlsl)ecies 01' ig~~anitl1iz;n-tls. For inany years the gcntcs W;IS ;I 1;11.g-er;III(I ~)t.~I);~blyLIIII~;I~III.;I~ one until h/littlem;in (1942) s~~ggcstetl11r;il it I)c tlivitlctl illto fotrr gener;i, viz. Uln, Urosa,~rr~~s,St?-epto- ,scrr,rlrs, ant1 I'cl~.ostl~l~rrs.l'he t;txonomic position ant1 validity of these have been \,;triottsly regartlet[ by L,o\\le (1955), Savage (1958), Carpenter (1962), ant1 I I)~~r~.ows,01. al~~.~tl)s is ;ilways a c.ornn1o11I'c;I~III.~ ol' III;I 11.'I 1)ltat. ' 'I'l~roltgho~~ltheir range, 11t;is ;ri.c rcl;~tivcly;111111l(l;lllt. They arc scltlom cxccctlctl ill n~~~ill)c~.swlle~.e~er they oc.crll., ;III~~ill niany loc:~litiesmay be by fa^. 111c most :rl~~rritl;in~sl~ccics of li/;~l.tl.111 f;rcr, rl~is~I.C:I( ;~l~l~ntl;~lic.e;III~I c.onsl)ic.rlorls~lcxsli~.sl atl~-;ic.tctl niy ;~ttcnlioll. So~nc(11' tllc 3.1xjss l';~ctorstI1;it 1i111it 11iv gcog1-:11)11ic.(Iisl~~il)r~tio~i of ~JIIL a1.c the (;l.c;~tPl;tins ;\n(l nlo~~nt;ri~isnltrc.11 ;rl)o\~6000 feet. Grasslantls ;II-c gc~~e~.;~lly;I I);II-I.~cI., :rntl r IIC low c oltl lolcl.;~nc.cof tlic sl)ct ies I-estl-icfs it ;tltit~~(Ii~~;~lly;111il I;~titi~tli~~;rlly. \'\ii~l~i~~ ;I]II);IITI~~I~ si~it;rI)lc ;II~C:IS, co11111eti- ti011 wirl~o111c1. s1)ccics II~:I~l)c ;III ~III~I~I.~;III~I';ICI~I. Ii~iiiti~lsirt;is. 111 x,vesrrlm 7'ex;1s, f-lolbrooki(r ~~l~cc,rllntn,;inotl~cr sln;ill ijiu;~l~i(lli/;~l.(l, is the t1olnin;rnt sl)ccics ol' the High P1;rius gl-;issl;intls; it ;illcl (//(I arc aliilost always ero- logic;~llycxc~l~~sivc, r holrgh 111.o:rtlly synil,at~.ic..In the western United St;ires, S~(~/O/II)TII.Pgr~rr.io.srt.s is 111ctlornil~;tol 1iz;irtl in thc dry plains. This species, loo, is bl.o;~tllysyr~ll)al~.ic wit11 7110, 1,111 it is :In cxccptio~l;rlsitt1;rtion where they occt~~togctllc~ in ~rc,r~lyeclr~,rl ,~ljr~l~tl,rntc. \\Jitllin the l~ioatlhabitat li~i~irsol' ~~t;is,tl1c1.c a1.c solile ;issoci>rtions iri wllicl~lllcy ;]re rarely Eonntl. 7'llcsc intl~ctlc 1.otky ;II.C;IS wit11 litllc vcgcr;r(io~~;rntl hc:~\.ily shatlrtl 01. ~rootlctl;i~.c;rs. IJti~s ;II~ strongly hcliotlicr~rlicand ;tvoitl sl~;~tletlarcas even in tlcse~.ts,wllere they AI-C unco~~~moiiin tlense thickets. :Ilthough no experi- ~rlentalstutlics oS habitat prcfercncc in this lizartl (or any other) ha\.c been made, I think t11'1t sr~c11 woultl tlcmonsti ,~tctllc I)ESCRII>TION OP. -1.~11' STIII)YAu~:~s.-Most of tllc inIol-nl;rtion ~I~CSCIIIC~ here was c.ollectct1 I'rolri tl~c;rrc;r ;rronntl Kermit, \4'inklcr County, Texas, ;~t an elevation of 2!)00 Fcct. 'l'wo st~~tlyarc;ls 1oc;ltetl two nriles apart in similar 1i;ll)itat were gl-itltlctl witli lcttel-cd ant1 n~~rnbercclstakes set at interv;~lsof 20 feet. Eacl-I area w;~s:I scl~r;rrc100 yartls on a sitle, bout 2 ac'l-es. 7'11~type ol h;il~itatis sliown in Plate I. Slrol-t ~riestluitctl.ccs (Prosopis j~rliflora),yucc;~s ()'~tccn sp), s;rntls;rge (/lr/o~ri~io//lifolicc), l,roornwcetl (Xn~7tItoccplial1r~~z snrolhrt~e),;rntl sllinoak ((11rc1.c.rl.csp.) itre the tlorninant plants. There arc few n;ttive grasses relri;lining in tlic irrc:l, hrlt this w;~suntlonbtedly the 01-iginal dominant vegetatioir. C)vcrg~-;r/ingc-o~~pletl wit11 an ~rnstablesandy soil has let1 to deterioration of tlic 1lahit;rt. Howe\rcr, before the demise ol the grass1;intls it seerns likely that {Jtn W;IS sc;n-ce in this area just as it is in the less clisturbetl grass1;tntls tlr;~tstill exist in part of wetern Texas. In any event, Uta certainly occ~rrretlin the liearby Chihuahuan descrt from which it may have been a recent invader. T11c 11l;lnt c.o\.c.~.has I)c.c~rc.hti~i~;~~ctl ( I inklc c,t (/I., l!)(i?) ;rc. about 20 pel- tctit of the grotrntl ;II-c;~,so (II;IL nir~c.l~ol rlic study al-eas is I)al-c aeolia~~ s;~l~tl.Followil~g stlnllriel. I-;rins 111e1.e is ;I gl-c;~ti1ic.1-c;~se in 1)l:ult cover by ;I \/;~~-icty01' ;1n1111;tl~lectls antl, sc.c~llingly,;I concon~~nita~itinci-e;~se in thc c111;rntity ol inscc.ts. 7'hc ilre;t is c II;II-;I( tc.~.i/etlI)y hot st11rlli1e1-s;111tl milt1 wintc~-s~rit11 free~ing tc.1111~e1.;1tui-cs])~.i~li;~~.ily ;kt 11igl11. llo~vc\~~r, t11c gcogr;~plii(~ positioli or this area ;I( tllc sor~tlic'~.~~cntl of the <;t.e;~tPl;li~~s, tlic lo\\r h~~~nitlity,;inti the ~iiotlcl.:~tc;~ltirtrtlt: 1n;tkc ~)ossil)lc\,cry sutltlen ant1 ~.;~tl~ercxll.cme tempera- tt11.c c.h;tngcs ;IS I~igli~,ressr~~.e systc~ns l'ol.ce c.oltl air soutllw;ll.tl do~vnthc <;I.~;III'l;~ins. DIIIing this stutly I Ii;~\,cI-ccoi-tlctl tcir1l~cr;tttrres tlo~.\~~ito -12" 1; ;11it1 ;IS liigli :IS 120' . F171~c.~.:~i~il';~ll ;~\.et.:tgcs i~bor~t 15 i~lt-l~csa~~nu;~lly, niostly in six-ing ;~ntlSIII~I~~I.; s~~o\~rl';~ll r~su;~lly occn1.s eac.11 ye;11-,hut is a neg- ligil~lcso~t~.tc of nloist~~l-c.High ~li~itlvcloc.ities are ch;~r;~c.teristicoS this ;IIGI ;111tl res1111ill t~o~isi(lc.i;~l)lc.l)lo~,vi~~g ;11it1 tl~.ilti~igoS the 111ista1)Icsa1it1 so t11;tt Irig11 tlr111cs csist in se\.c~.;~l])l;~tcs lic;~~. thc str~tlyarcas. ~III.IIOI)S01. I\'oI nently ~n;~r.ketl1)y c.lil)l)ing 1111 to foul. toes. Nct,c~.we1.e ;~tljacenttoes clipped, 1101. 1r1o1.e tlli~ll tu70 011 ;I single fool. 71'lle system t~sctl was a silnple one 1.ecluiring 110 ~)rct,iollsexpel-iencc to 1.eat1 the toe-clip numbel-s (Figun-e 1). 71'lle 1111n1l)crswc1.e rc;~tl;IS the :~ctrl;tl 11urnl)ers of the toes removed. Thus, ~.emo\,;ilof toes 2, 7,ant1 1 1 ~vot~ltlrest111 in nl11nl)cr 2-7-1 1 . A11 adtllt lizards \vcl-c 11;tintctl \\!it 11 ;I (list inct ivc: insigni;~(Fig. 2) with one oi t111-ce easily \,isiblc colors. Slledtli~lg~.es~~ltetl in (.onfusion ol insignias in some cases, I)~IIt~st~;~lly the ;tl~irn;~l's ntllnl~er coultl I)e determined by sighting the insig- ni;r ~litllo111tlic ~lecessity01' COIIC~IIUOIISIYchasing and 1.ecapturing it. 11(.. I. 1,cIt 11;11i(l;III(I rig111 foot of III;I to \IIOMJ s~(~II~,II(~of to(, I~IIII~~I~I-~II~.Notr that tl~c,Io<,s arc 11111111)c1~1.(1f1o111 111~. i~~\i(lr0111 011 1I1e f1o111fool ;i11(1 f1.0111oiltsi(l:. ill 011 Ihc IC;IV. 'l'l~ils,III~. i-ig111 11.o11t foot ~V~IIIIIIl~(,;ir toes (i-10, Ill(, lrft 1-v;ir 11-15. \'ol~nfili/artls wcl.c not gi\,c,11i~~tli\,itl~r;~lly tlistint ti\.c i~lsigliia,but were l);~i~ltetlwit11 ;I small (lot on tl~c~I~I-~IIIII I)C~IV~CII ~IIC 111iglls. I':;~t.h time the ;II-~;I w;ls wol-kctl, o111y tllc III~~);I~IIIC(~yo1111g l~~'1.e (;I~)IIII.c(~. T'lieli, at about I wo-~vcckilitcl.\.;~ls, all yo~111gwc.1 c (.;I~~LIIctl I efi;~~~clless01' co1t)r ;111(1 repaintetl wit11 ;I tlille~.ct~itc.olo~-. 111 t l~isway the re( ;ll)tul.es oT yor111g;~niln:~ls c.o111tl be I~cttcrs~);Ic(Y! ill li~nc10 l)ro\,itlc i~ll'oln~alioll011 g~-o\vthI.;I~CS, ~novements, ;111(1slletltlillg 1'1 ccjtlcnc y. 'I'llc tlir~c, ti~~~col (lay, ~)osi~ion,sno~~t-\.clit leng111, ~;rillc~~gtli (both ~.r.gc~ic~.;~te(l;11lt1 ~~n~.cguic~.;rt"I I);II.IS), ;III(I shctltling co~~tlitionwere I-ecol-(led ;rL c;~c.Iic.;ll)cul.e on ~xili~ctltl;~t;~ sl~eets. 111 ;rclclitiotl, (IIII-ingsornc periocls the ~.cl)~.o(lucti\.ec.oritlitioll ol' r;1cI1 leiuale w;rs tlcter~ni~~ctlI)y careful palpation ol IICI. ;~l~tlo~~len.I;i~l;~lly, ~t~cigl~ts were rcto~.tlctlfol. e;~c.Iili~ilrd ;it pe~.io(lic ir~tc~.\,;~ls.Fol. tlris ~~ul'l~osc,li/al-(1s wel-c pl;rtctl in n~~lnl)cl.ctlvials ;iftel- (.;I~CIII.C;IIKI t;~ltcnto ;I slleltcretl 11lac.e in a Tvet clolli bag. ?l'lle lilartls were weiglietl to the nc;1res( .O I g11i ant1 ~.etllr.nctlto tlieir original location. rTc~n~)cr;~t~~rcswere [;(ken ol nurncl.ol1s li~ai-tls(luring this study, all of rl~e~ri~vitll ;I St.lrr~ltl~eisc.lo:~c.;~l tl~c.~.lnolnete~-. Nearly si~n~~lt;~rieousternpera- tl~rcswe1.e ~.ecol.tlrtloS tl~cail. ;~ntlsl~bstl.:~te at the li/al.tls l~osirionof captul-e. In all of tile :~l)o\,e,I occ.:~sion;~llySelt th;rt lrly o1\r11 clisturbance of the allilnals Intlst Ir;lvc all ellccl oli the results. Tl' so, it is a criticism tl~atcan be lcvcletl ;it ;11111ost;uly study. I Ir;~verlo objcc.tivc cvitlence tli;rt any aspect of tlie biolo~yof' the :1riil11;11MGIS I~cil~g~llotlifictl. However, Itre tlitl solrlctirnes tl;r~ringetlie stutly arc;~stllen~sel\~es ill c;~l)t~ll-ingtlie lizarcls. To conipensate 101. this, on sevcl.;~loctasior~s ~vc I;~l)o~.io~~sly rel~lantecl ylrcc;~sant1 othe~. l)l;~r~tstli:~t tvc hilt1 cl;~~riagetl,r~silix a tlet;~ilctlvegetation niap ol the study ;II.~;IS 111;lclc 111-iol.to the stutly as ;l guitle to the severity ;tntl location of tl;un:~gcd ;u.e;ls. ~~I,:TIIOI)S01.. LAIK)I<:\.~OI Only tl11.c~speties of li/;tltls, otlrcl. 111;t11 lll/l, were c.on11no11 or1 the Tes;~sst~rtly ;trc;ts. 111 ol.tlcl. of 1.cl;ttivc ;rl)~~ntl;t~~c.e,thcsc were the whi11tail (Cnrrni~Lof~/~o~.~[.s~igri.~), the Ilornccl 1i~;trtl(P/I ryrr osotrrtl cor?71rl~i~r~), allcl tlic 1eol);wtl li/;~l.tl ((:~.otn/~l~)l/rr.r70islizc,r/i). 'l'lle only otllcl. li~ardscncou~ite~.etl were occ;~sio~l;tlElrrt~c,c,r.s o0.solct~r.s ant1 Holl~rooltirr~r/crc.~tlaln. pl'lie Ieol);t~.cllir;u.tl is ;I 1;tl.ge p~.ecl;ttorysl~ccies whiclr we know cats ut;ts on occ;~sio~t,though tI~c1111lk 01' its diet c.onsists of I~tl'ge;II-thl-opocls, principi~llygr;tssllol~l,el.s ;inti \v;~lkingsticks. Tllere were us~~allytwo ;~dults ant1 sevcr.:tl yo~tl~gIcol~al-(1 li/;~l.cls seen oil the stucly ztreas tl~rringeach slllnlner, b11t not at other sc;tsotls. l'he ~vhil)t;rilli/;tl.cl is ;tlso :L l;tl.ge species tIl:~t, ~vl~ilcactive, is ;iIniost col~ti~iuo~~slySol.agi~rg, so~rieti~t~es in gl.ollps. 'Tl~is species a1jpe;il.s i11 the spring (usually April) and 1l;ts :I \.el.y sllort ;~l)ove-grol~r~tlexistence; ~llostoS tlie ;tclults clisappe;~~.by ~rlitl-to 1;rte sulllmei. ;mcl the j~~\.enilesare gone 1)y October. Tlle Ilornetl liL;u.tl is l';~irly ;I~>LIIIC~;II~L,11111 is seldoln seen. It is much more colrnlion ill tlie sho~.t-g~~;tssl)l;~ins, so the Ilabitat near Kermit is prob- ably ecologically rna~.ginallor this species. It is seldom encountered far l'roni the coolc~.1);irts 01' the stutly ;ireas-thc dense mesquite thickets and p;~k~.:it~rcsts. It is seltloul sccu lnovillg ;\bout in the area. None ol ~llcsesl)ec.ics, I think, I.epresents ;I serious (.ompetitor of Uta, except the whiplail li/;~rtl.rvlien yor~ng,but sue11 coml~ctitionwould exist only for a s1io1.t pe~.iotlof time no[ only bec;iuse oS the short activity season ol' the ~vlliptail,but bec;~~~seit r;tpitlly ;ittains a large six. The leopard li/;trtl is :In ell'ectivc pi.ctl;~toron 110th juvenal and adult utas. Scvcl.al snakes ill tllc ;wca a1.e 1i~iu.d predators. These include the c.oac.lrwl~il~(i\/ltrslic.oplt is /I(rgcllrr~~r),;I 1;rrge ;rnd active diurnal species; the lx-;li~.icr;~ttlcsn;~ke (C,'rottrlrrs uiritli.~),p~.i~na~.ily c:rcp~~scular and nocturnal; tile ~iigl~tsnake (IIypsi,qlcrrir t ortlrrtr trr), a small rear-fanged and semi- fossorial species; ;~ntltwo se111i-I'ossol-ialspecies ol nlctlirim size which are abu~~tl,~~itin 11lo51 s'tntly '11c~t5ol westel11 Texas ;rntl active primarily at night. 'l'llese 'uc (lie glo9sy sn'tkc (Arrzor~c~rlcgtrlrc) and the long-nosed snake (lilrzlror lrczlrr, lcr or1 tc~).All ol r l~cscspecies have been t'tken in thc study areas. Det;riletl ~.cco~.tlsof ~)l.etl;~tiollwill 1)e tlisc~~ssedin thc section on rnor- lalily, but it slloultl be 11orct1I1el.c tllat tllcre are ~~un~e~-ouspredators present in abuntl:tnce 011 llic area ;III~I ~II:IL variot~sones are active tllrougllout the cl;~yant1 ~~igl~t~.e~itIel.i~ig II~;IS \~11111c1.;1blc to pre(1;ltioli at 2111 times. i\vi;tn l)~.cd;~torssi1c.11 ;IS slll.ikcs, ~.o;~tll.n~~ncrs,iind Ila~vks were rarely seen ;ti-ountl tl~cstutly ;II.~;IS.7'11e bcllaviol ol utas is such that they woultl p\.obably seltlolri I)c cal~ghtby 1)irtls. 'l'lley r~trelyventure into the open ant1 on sucl~oc.c.:tsions tlley l.al~itllytl.avel.sc tlle open grountl to rcacll sheltering vegctiitio~~.Even wl1c11 l):~skirig,IIL;IS t hoose loc;ttions in tvhich they would I)e I-elatively i~~\,t~lnc~-;~l)leto ;lel.ial ~)~.etl;~tors.Finally, to be discussctl later, is the invcl.se i~latio~~I)etwcell I)otly te~nl)c~.at~~l.e;tntl ~viu-iness in ntas. Tj\Tlle~l tl~ey;II.C cool, ;III(~ I)I.CS~III~;IIJ~~11101.~ \~t~lnerable to ~~rctlation,they are also 11101-c1v;ll.y tl1;111 TVII~II tl~ey;II.(! Tval.ltlcl-. 01ie of t11v nlost inll)orr;~ntilrtel.itctions is an indircct one. The most co111111o11III;IIIIIII;I~S OII tlie str~tly;ll.eas ;II.~the ~,ack~.;tt(I\'cotor,za lrzio-op~rs) ;III~~tlie kalrg;~l.ooI.;II (1)il)oclorrr)l.s o~tli).'I'he 1x1c.kl.a~~cover their nests with rllornlolls 1)iles of tlel)i.is, ~~st~i~llyin nlcscluite thickets. T11c kangaroo rats clig este~rsi\se t~r~~llcls(li~.ot~g:.llot~t the s~r~cly;II.~:IS. Ihth the ttrnnels and II;I&I-;I~ ncsts p~.o\~itleexccllellt ~)~.otecti\~cshcltel.~ Sol- utas. 'I'l~ere is 11o cluestiol~tl121t tlle li/:~~,tlscluic.kly 1c;ti,11thr loc;rtio~~sol the nests and tunnel ope~li~igs,;111d will titkc slleltcr ill tllem ~vl~eatlisturbed, 1x1-titularly during the W~IILCI.~noi~tlls. 111 wir~tci.,we have tlug 1;u-ge ~ILIII~~I~I-s01' 11t;ts Sl-o~ll tem- porary hibern;~cul;~in tllc s;~ntly1-iins ol' the l);~ckl-atIlests. Not only does the activity ol the ~ll;~rn~rlalslooser1 llle s;~~lcl;ulcl 111;tke~)cnctl-;~tio~l by utas simple, but the ;~(lj;~ce~rtnest 111.ovicles sl~eltel.Sol- the li~;~rcltl~t is still somewhat torpicl alter c~llcrgi~lgSrolrl the s;uncl 011 war111 clays. I think tllat these nests ;me1 turl~lclsystelns are ;tlso irlll)ort;rnt ;IS l'ootl rcse~.voi~-slor the lizards, lor co~~ce~~t~.;~tio~lsol' illsects 111;1y so~~letimcsbe l'o~~l~tlill ~lle111 eve11 during :.he wi111el.. 'I'IIE ~ 'I'he first signs of tlle beginning ol' the i.cl)roel~~c.tivc( ycle in fclll;~lcs;we cll~ulgesin appea1,;tnc.e oS tlle o~';t~-i;~nfollicles. 'l'llese ;II c s~~i;~ll(1.0-1.5 111nl) and translucent in ~lon-l.cl)roclucti\,eSe~~l;~les, but in tllc c;~l.ly sl)~.irlgtllc follicles lose their tl.;~nsl);ll-cllc.y;illel ljec.oillc so111~~~11;ttnlilky ill ;II)I)C;II.;III~~, This cliange is soo~~follort7cc1 by ;I progl.cssi\~clyyello~~vct. (0101.atio11 ;IS 111o follicles 111ltlcl.govitcllogenesis ;~nclI-al~itlly cnl;c~-gc to ;I tli;~lrrete~.ol' 7-8 111111 at the tiiilc ol ovt11:1tio11.;ll'tcr o\r~~l:t(io~~,;I co1.11t1s ~IILCLIIII I'or111s ;III(I I.~III;I~IIS tlistinct until ovipositior~,~IIL (legcr~c~.;ttes ~.;~l~itlly tl~e~.c;~ltci~. 1111111e(li;1t~ly l'ollowirlg ovil~ositio~~,;~llotliel. set ol' l'ollicles ulltlel.gocs \,itellogc~lcsis111e- l~;n-;~toryto the clevelol)~ric~lt 01' the Ilext clut(.lr 01' egg\. l '1'111~ ONSETOF ~ '1'111.:~ I Taking the data of all 418 fe~nalesex~uminctl, the average clutcll size is 3.91, but the mean clutcll sizc is greater ill larger lernales and larger early in the repi-oductive season thai later. The latter is ti-ue regardless of sizc, lor the :~vcr;igcclutch sitc for all oS tlic six gror~lxdeclines tluring the sunimer. Reasons for this decline have alre:~tlybeen suggestecl, I)ut it slloulcl be ~lotcd here that the frcclueucy of follicular atresia is iloL 11ig11 enough to account for his declirie in clutc.11 sitc. TAII1,E 1 A C:~MI>AI ~ ~ - -- 1959-GO 363 10 69 2 1 4.0 June, ICKY2 15 7 86 7 3.3 July, 1962 35 11 (i7 22 3.2 AUK,, l<)ii2 I :i 1 4 X (i 0 2.8 YEAR-1'0-YEAR VAKIATI~NIN CI.UTC:II SIZE.-TI~C 110ssibility 01' tlifferenccs in average c.lutc.11 size in tlifferent years was investigated, using only samples that wcre st~fliciently1;11.gc (Table I). The mean c.lrrtcl1 sic calculatctl from sa~nplesn~;~tle in 1963 is higher t1~1nthat Sol- c.o~ill)ar:~l)lcrnonths in 19(i2 01- 1964. Although various reasons lor this tliltcrc~icemight hc postulated, there is ;III obviot~sc.ol.~.cl:ition oL the tliffe~.ences with the average si~eof the I'cill:~lcs c.o~~~l)~.isi~~gthe s;~~lll,les. 7'hc proportio~lof females i11 the 1a1-gest si/e gl.oul) (50-5.1 111111)is I~igllc~.ill tire l9(j3 sam1)les than in the other two ye;il.s. 'l'lris si/c tl;~ss11;is been shown pi-eviously to have ;I higher mcan t lurt 11 si/c tl1;111s111;111c1. ones ;111tl tliel-eforc s;iillples containing a high ~)l.ol)o~.rio~~ol rllcsc I;II-gctfcm;iles will give a higllcr estii~lateof clutch six. It is ol)viot~sI'roirl these tl;it;i that st~rtliesof clutcl~six ill lizards must t;~kcillto ;I(.(.~IIIII LIIC si/cs tlistrib~~tionsin tllc ~)op~llationsai11l)lctl ;is well as sc;~so~r;rltlille~.e~rtcs tlr;~r ;IIY i~ltlel)er~tlent01 si~eof the li~artls. n'lln/ll%l~.l<01: (:l.ll'r~:llb:~ANI) 1.I:NGTM 01: REI>ROI)UCTI\II.:SI~:ASON.-~~'~C ~.el)~.otlt~cti\,c~)o~a~ti;il c.;~ll~lot I)c esti~natetll'ron~ clutch size alone becnusc 111;islay scvc1.;11c.1t1tc.llc.s pc~. SCCSOII. Hence, the lerlgtll of the i~eproductivc sc:tso~~is i~rll)o~.t;~nlill (I~r~~.~r~i~riilg tl~c11t11nber of possible clutches. 71'ii~klc(I!)(; I) tlcli~ictlthe 1.el)imtluctive sc;~sonas heginning at the time rlrc 111;ljol.ityof I'cill;~lcssllowecl sigils of vitcllogenesis ;Inel extentling to the ri~newllen tlrc ~n;ijo~.iry l)ostrel~rocl~~cti\~e,i.e., when the ov;rries no longel. t.011 r ;I~IIcnl;~~.ging I'o1li(~Ie~ th;~r ;Ire i~ntlergoingyolk tleposition. In 195!) the se;tson so tlcfirretl extenclctl to 141 clays, in 19(i0 to 12 1. The tinle rcclui~.ctllor tllc tlcvelol)~ncnt ant1 ovulation ol' ;I clutch was estirnatetl ;IS 37-38 tl;~ys.Divitli~~g tlris 1;itter fig111.c into the length of the season and ;~llowingtltrc time for ovitlr~c.;il1-etc~ltion ol' tlrc eggs 131-iorto laying intlicntetl st~ll~c.ie~~trime Co1. c.111fc.llcs. '1'11;it intlivitlt~;~ll'c~~~;iles clicl intleetl lay more th;un ;I sirlglc clutcll was ~)~'cclic.tctl~II two li~rcs01' cvitle~lc.e:(1) some l'elnales containetl coi-l~or;~ 1111e;ri~~tlic.;~ti~rg 1.ec.clrt o\rul;itioir anel ;ilso contained enlarging, yolked l'ollit les; (2) tl~c~l~;~iol.ity of le~rl;~lcs ill evel-y s;irnl)le ol lizartls taken (luring rl~eI)~.cctli~~g SO;IS~II I'vc.1.e ill sonic st;~gcof rel)rotluction, ;I fintliiig th;~two~11tl I~;r~.tll~,I)(, ~)oshil)lcIIIII~SS rlrc l'cr~r;ilcswele ~)~.otlucingIIIOI.~ th;i~r one cl11teI1 ol egg. 1'1-ool 1.01. ~ni~ltil)lctlt~tc.lrcs (.:1111c l'ro~np;tllxiting fen~alcsin the field c;it 11 tinre rlrcy \\rc~.c~.cc.;~~)t~~~.ctl. \'\'c loi~~rtl it 1)ossil)le to diKerenti;~tcI~etwcen o\,itlt~c;~lcxgs ;iirtl 1iil.ge o\.:t~.i;~nI'ollit.les :inti even to juclgc accul-ately the si/c ol rllc l'ollit lcs I)y ~);~ll);irion.1)y opening I'cnr;tles in s;rn~l>lescollcc.tctl ;IW;I~II.~III tlrc sri~tlyii~-e;i ;il'tc~. they 11;itl first Iwen p;ill);iwd, we were ;~blc to c.o~~\,i~~c.cor~~~sclvcs ol tl~e ;I~(.II~-;I(.Y ol this tech~~icltie.Not o11ly ditl tlris ~llcrl~otlsr11)l)ly i~~lo~.~lr;~rio~~o~rtlrc! n~111il)ei. of clutc.lles laic1 by single l'cn~;ilcs,1,t1t ;ilso ~vith;I 1rle;tsul.e 01' tl~cti~rle 1.ecl~rirect to ~):tss th~-o~igll \1;11.io11sst;~gc.s ol I'ollic.lc e~ll;~i.ge~~~e~lt.It MJ;IS, of (.ourse, II~~IISII;I~to c;itt.ll ;I fe~ll;~lccs;~t.tly 1)1,io1- to ovill;ilio~l1'vvit.e in st~cccssion,but by pooling t1;rt;r I'I.~I~sc.\rc~.;il I'c~~~;rlcs it W;IS 1)ossible to ~.cto~lstrt~ctthe cycle. 7.11~esti1n;ltctl times I-equirctl for clevelol~i~w~itoT tllc eggs in the ov~ry,for ovul;rtion, ;rntl ovitluc,al retention arc shown below: 71'llc ilvcl.;tge of ill1 of tllcse re(-ortls is 48 tl;rys. E1evc.n esti~ll;rtcsof the time tlurirrg wllich cggs rem;rinetl in the ovicl~~cts;IVCI-;rgetl 13 tl;~ys.IT this fig~~l-eis ;~tltlctl to tlly I)I.CV~O~ISesti~~~i~tes of 37-38 d;rys recluiretl J'oI- egg tlevel- olxilc~ltto ovul;rtion, a total ol 50-51 days is obtainecl Cor tlie total time i~lvolvetlin one egg ~)rotluction-l:~yir~gcycle, ;I figul-e not g~-e;~tlytliffel-cnt 1.1-~III the -18 tl;~ysesti~rl;~tetl by ~);rlp;rtio~~. :ll~l~;wet~tly;L slio~.ter pcriotl t1i;ln the ;rl~o\,cis ~.cclr~i~.ctl1;1tc1- in thc scilson. For the pe~.iotlfrom March tllrough i\pril ;In csti~ilatcof' 50 t1;rys wi~sobt;~inctl, but l'or l\iI;ry to Aug~rstonly 41. Tliesc ;rtldition;~lfigu~.cs in(lic.;~tetll;rt ;I[ le;rst three clrrttlles ;II.C l)ossil,lc ill any sc;rso~ltli;rt extentls over 21 periotl ol' abo~~t,I montlls. hcttr;rl figures lor tllc length or the 1-cl)ro- tluc.tivc sci~so~~in tlillc~.cnt ye;rl-s ;Ire: 1!)5!), 1/11 cli~ys; I!)(iO, 121; I!)(iS, I(iC,; 1964, 159. /\ few fc~n;rlcswcl-c c:rl)tlcrctl irt it~tc~.v;tlstll;rt were esl)cc i~rllyp~-opitiot~s ill illtlicatilig the nu111be1- of t.lutcl~eslaid. 1)ct;rilctl tlat;~ on these ;Ire l~rcseiltctlbelow: I. :\l)~.il20, 3 ti1111 Iolli(lcs; ,IIII~CI. o\i(l11c;11 t,gg\; ,11111e13, eggs jlisl 1;iitl; J111y 26, eggs jiiht l;~itl. 2. /\lll-il 10, ovicl~lc;~leggs k~l;~)27, ovitlc~calcggs; lul) 26, o\~itlrlc;tlegg. 3. ~I;IICII2!), 1;11.gefollicles; ,JIIII~2 I, 1;irgr lolliclcs; I\II~IISI2, iilsi 1;iicI. I. RI;II.cII:10. 1:irge follitlcs: ,IIIIIC 16, I;II.:;c follicles; July 18, I;isgc follicles or ovitluc;~leggs. 5. RI;II.cII 29, I;~l-,gcl'ollitlcs; ,Jilnc 30, la)-gc folliclch; ,\II~IIS(11, ovidi1r;il cggs. (i. Rli~l-cl~YO. I;II~.c follicles; JIIII~.9, ovitl~i~~lcgxs: July 20. ovitluc;~lcggs. 7, ;\priI $1, ji~st I;ticl; ,11111~2, (~\i(Ii~c;ilcggs; j111y 12, ovitl~~c:~leggs. H. Al)sil !). ills1 1;ritl; WI;iy 18, large folliclcs; 1u11c4, 4-111111follicl~s; JUIIC 20, ovicli~calcggs. 0. ,41)1il I), I;~rgcslolliclcs; ,]line 2, 3. ovitlucal cggs; July 28, o\itlucnl eggh. 111 c;~c.llol' these !) ins~;~~~cesthere is cvitle~lc.efor ;It least 3 clutches. 1 11;lve cal(.t~li\tctlthe theoretical time tl\;rt shonltl have bee11 ~ecluiretlIor each of these l'ern;iles to pass thror~ghall of the 1-el>rotlr~ctivestages at which ~hcywere observetl ;ir~tlhave comparetl tllese ti~rlcswith the actu;rl period il~volvetl;IS sl~ow~~below: Nrrlnl)c.~.s3 ;111(1 3 51101~ti)? g~.e;rtcst tliflerencc I~ctweenol)servctl ;r11t1 ~I~c.o~.ctic.;~ltIetc~-~ni~l;rtioris. Nr111111e1- 3 W;IS ~.e(o~-(let1;IS I-ecently laid when (YI])~III'~(~011 iiugrlst 2. Howcvcl-, ;~ssr~~nitlgtll;rt this fc~il;~leW;IS now post- rel)~.otlrrc.ti~~c,the egg5 t.orrltl Il;l\-e heen 1;ritl 1n11c.h bcl'ol-c ;\ugust 2. Nrr~nbcr 5 nxry 11;lvc l;litl 1no1-e tllan 3 clutches; this worlltl cx1,l;rin the long actual ti111c con~l);r~.ctlwith the tlleo~.ctic;~ltilrlc, lor we may simply 11ave failetl to (.;I~)~III.c(he I'cn1;rlc (1111.ing011(* of' ller ~.el,rotluc-ti1.csecluenc.es. I7lle o111y ~v;~yto cleterniinc ;tc.t.r~~~;rtelythe ntrnn11c1- of clr~tcl~eslaitl is to c.;ll)ttrl-e ;111 I'cirl;rlrs ;I[ rcg111;rr interv;rls ;tntl weigh them at each caj1t111-c. 'l'hc. females lose ;rbor~t25 per cent of tlrcir botly weight al'ter egg tleposition so I~I;IIt11c tinie 01' l;ryir~gsc.;lrl Ile cletcl.~ninc(lin this 1v;ry. This sllonltl 1)e tlonc in Iny strltly ;r~.c:rs,for it is still l)ossible tllat 1 ;rln untlcrestirnating tlic ~~rrrrll)e~-01' cltrtc-hcs. FOI-cx;unplc, le~n:rle no. 2 on the previorrs pages w;rs ~.ec.ol.tlctlavitll o\~i(lnc:rlcggs on April 10, Rlay 27, ant1 July 26. This is tlclinite lo of th;rt alre 1;litl 1111.eeclr~~c.l~es, I)ut there is also the possibility rh;rt one w;rs I;ritl 1)etween tlle Wlay ;rntl ,[111y c.;rl)tIrrcs ant1 anotl~ersometime ill .\rrgt~st. 71'llc cvit1cnc.c for ;rt 1c;rst 3 c.111tc.hes ;r\,ci-aging ;rbont 4 eggs c;rch is ovc~~wlicln~i~~g.~II;ISIIILIC~~ ;IS ;111nost every fern;rle ir~the popcrlation is sestr;rlly 11i;itrrre ;rt the oliset 01' rlle 1)reccling season, it l'ollows that each will lily 1 :! eggs pel' sc;rao~~.I think 1.01- I-c;rsonsgiven ;rbo\,e th;rt this is ;L minimrln~ ligrl~.t,;III(I it is less 111;rn tlie ;rve~.;rgcI~IIII~~)~I- 01. 11~11cllliilgs per I'en1:rlc mat-ketl in llle strrtly ;Ireas c;rtli ye;rr.. Hcnc.c, I 11esit:rte to use the figtr1.c~above to c'sti111;rte tlic tl~eo~.c~tical11;rt;rlity. 1 ;II~hesit;rnt, also, because of data c.ollcctetl 1'1-o~nfe1n;llcs iso1;rtetl in the 1al)oratol.y. Onc of' nly strrtlcnts, (:rrell;r~- (ll)(i(icr) collected female utas containing ovitlrrc;rl eggs, allo~vctltllc~n to 1;ry a~itlthen isolirtetl thein until they laid ;lg;rin. Elc\wx ol' 19 l'cm:rlcs 1;ritl 2 c.lr~tc-liesof' cggs c;rtli ;tntl 7 of thcsc 11 laitl 3. A toti11 of 47 t1;rys elapsetl between the tin~ethe first lernales laid the (11-st clrrtcll ;rntl tllc time they tlepositetl a secontl, b~~t1)etween the second ;rntl thil-tl an ;~vc~-;lgeof only 25 (lays was rec.ortlet1. Thc time for tle\ieIopment of the i~~i~i;~l(.I11t(11 W;IS II~;II- 0111. theoretical esti~ll;rrc from tllc ficltl, b11t tlic tin~c1.ecluiretl for tlevclol~~~~entof tlie t11i1-tl clutch was ~.cmark;tbly short. IT auc.11 ;I shol-t i11tc1-\~;11existecl in tl~cfieltl, ant1 such h;~sbee11 rcl)ortctl to 111c l'or utas in Nev;~tl;tby Iloddenbac-h (11e1-s. comm.), tlien my cstiln;~tcsof the nl~rnl)e~-of (lr~tches 1;ritl ;II-cconsel-v~~tive. 1'11<101) 01.' ~'0~~~1~P,1~0~11~10~~~1,E(;(; ~)~~\~~~,OPA~~P~N~~'.-\~\'C 11;lVf3 OI>SC~\~~CI ;rc.t11;11egg tlcl)oaition in Ulo ,stc~rl.cOlr~.iciilcro~lly ol1c.e. \l\'c II;IVC spell1 I1ou1.s ill the ficltl digging ;111(l sil'ti~~gtt111.oug11 S;III(~ 1'1-0111 sites t11;1t we fell wcre suit;rl)lc l'or egg t1cl)osition bec.ausc of the large nun~berol lr;~tthlingsfo11ntl ;I~-OIIII(! 1hc111,hr~t wcl-e not s11cc.esslu1 fintli~lgeggs. \\re 1\;1vc ol)scrvctl cgg tlcpositio~lin tlie l:ll,or;ttory rn;iny t i~rlcs.1 J t as will ~IIIIICS~~;I~~II~I~lily 111cil. eggs in I~anksof ~noiste~~ctls;~l~tl 111-ovitletl in c;1cI1 c~I.I.;I~~III~. liy k11owi11g1'1.0111 licltl colle(,tio~~sol utas w1lc11 l'c~r~;~lcsfirst I)cg;111to tlcl)osit cggs, ;111(1 by kl~owil~gthe cl;~tcoil whit 11 hatcllli~~gsfil-st al>l~c;~~-ctlin tl~clicltl, I 11;1vcbce~~ ;11)1(* lo cstili~;~tcthc time ~.eclui~-e(lSol. tlevelol~mcntin 111c two yc;~i.sw1ie11 tl~c;111ove i~~l'ol-ni;~tionwas ;~v;~il;thlc.7'lic two estim:~tcs 21-c 6.5 ;111(1 77 (lays. It aecms likely t1i;lt Ilatchil~gtime of tl~e1:ttcr clutc.hes is f;rstel. ~II;III L~I;I(01' tl~cfirst bcc.;~trseol' higher sul)st r;~tetc~rlpcl.alu~-cs in sulnmcl.. 111 the I;~l,o~.;~to~.y;tt ;~l)out 30" <:, II;II t hing time 1l;ts v;rrietl il-on~ 59 to 79 tl;1ys. SI~ILc:c,s.-i\ I'c\\. ( 111tcI1es11;1\.e beell ~.en~ovetlI'I.~III fem;~lesto clctcr- III~II~tl~c ~vcights ol eggs pl.ior ro tlcl)osition. I'hese tli~t;~;Ire shown below (weight ill gl.;t~nh): 7'llc wcigl~c01' c;~c.llegg is only sligl~tlyless (Ii;~ntllc Ine:ln weigllt of the utas ;IL l~at(.Iii~~g(0.3 gm), rlle clillcre~rceattributable to rnoist111.euptake by tile egg tl~~ringincrrl~ation. 7'11el.e is 1-el;~tivelylittlc tlifl'ercncc 1)ctween mean egg si/c in c.lt~tcllcsc.ont;~i~~ing tlille~.i~~g nr~mbcrs of eggs. SIV:I<~IS.I,OI<,\(;I< IN U~,\s.-0111y 1-cce1111yII~IS s11c1.111 SIOI-;I~C: ill liz;t~.(ls been rcl,o~.tetl, though the l)lleno~ne~~or~in snakes llas I)ecn recogni/etl lor Inany ye;trs. One oS rrly str~tler~ts(C;ucll:l~., 19fG(1, 19Gf 11) 1121s lnatle ;I thorough slt~tlyof spel.111 storage in utas, the results of which arc cspeci;~llypertinent ;tt this ~)oi~lt.I I;rI1n (I lHi.1) h;~clshowri that regl-ession of the testes in utas is conll)letc Ijy 1;tte i\ugrrst. 71'llc tinle of latest hatching gives no intlication tll;tt eggs ;11.c Ijeing lei-tili/ctl Ijeyontl tllc ~)eriotlwhen m;tles are nornlally scxrr;tlly potcnl. l'ct, (:rrell;tl- (I!)(i(iO) tlenlonstratetl that fernale Utn stnns- 11r11.ic111ct store sl,cl.nl in sl)eci;tli/ecl ~.ecel,taclesin the o\*iduct.He has fc~rther l)~.o\.c(ltl1;tt these stol.etl spcrln are c;tl)able of lei-tilizing eggs in females iso1;ttctl 1.1-om111;t1cs 101. ;it 1c;tst XI tl;rys, irhor~tthe time I-cqrtiretl for thc tle\rclol)mc~~tof t~~oc.lr~tches of eggs. \'\'11y SI)~I.II~SIOI.;;~~ sllor~ltl be ;I ~lcll-tlc~,clol~ctltrait of a species in w~li tllc sex I.;I~io is C(III;I~;111c1 ill ~\~lli(.llthel-c exists a Sacu1l;ttive monogamy is not tle;tl-. (:cl.tai~ily,srtcl1 sto~.;rgeinsures l'crtilii.ation in the absence of c.ol)l~l;rtio~l,;111(1 III;I~IE Illis is sr~llicie~~tlyv;rllt;rble to prornote the evolution of S~)~I.IIIscol.;tgc ~.cc.cl)t;~(.lcs.011 t11~otlle~. 11;111(1, nly expel~iencewith the sl)cc.ics i11tlic;ttc.s tl1;rt a Icl~l;rlcscltlom f;tils to attract the attention ol the 1n;tlc clrt~.ill~;tlrc I)l.cctli~lgse;rson. On tllc contr;rry, c.ourtshil) attempts by 1n;tles ;tlw;~ysI';II. csc.c!ccl I lle I~IIIII~ICIof inst;tnces ill wlli(I1 the cor~rtsllil~advances of chc- m;tlc ;rl.e ;tcc.el)tctl I)y tllc fern;tlc ;r~ltlIc;~tl to c.ol~ul;rtion.If occasional (;ti1 losses 1)y I'cnl;tles intc1.fc1.e uritll co1j111;1tio1lthen ;I ~)owerllllsclcc.tivc lol.c.c cxis~s1'01- tl~ccl;tljo~.ation of sl)cl.n~stol.;rge. 'I'his l~ossibilitywill bc tlisc~r~ssctl;tg;t ill i~rthe scc I io~~on I)ch;r\~io~-. ~llr.or~gl~orttthis ;I(-( otltlt to oll'e~.sr~nlm;r~~ies ;t~~tl, in some inst;rnccs, critiques 011 111c. li~cl.;ttr~~.c.t-clc\.;1111 to c;tc.h section. Sr~cllliterature is sc;rtteretl ant1 11;ts nor I)cc.n ;~ssc~~ll)lctl01. ;rtlccltr;ttcly tliscussetl. I\ gc:11e1.;11~.cvic-c\l of ~.el)l.oclrtc.ti\.ccycles in ~-eljtilesh;ts not been written, ;tltI~or~gl~;I I;ti~.ly goocl ~IIIIIIII;II.~\v;ts l)~.o\,itletl1)y h~liller (1959) wl10 1.e- 111;11.kctltl1;tl ~.cl)~-otlr~ction 11;ttl 1)ecn strrtlietl in less th;rn one per cent of the (iO00 sl)ecics ol ~.cl)tilcs.1 tlortljt tll;~t this I)crcent;tge has been irlcre:tsed ;tl~l)~.(.(.i;rl)lysi~~c.c 1l1;rt tinrc. 1)11t IKI~I-~t1et;tilecl inSol-m;rtion is a\lailal,le for so111c sj)c( iext~~lsome gcne~.;rli/;ltionscan no\~be made. I h;t\~mittlc II~;tttcnil)r lo inclt~tlc;t11 litel-aturc I-ecortls of clutch sizc. 111 111c lil.st pl;tce, III~SIol ~hcmseem ~~le;t~li~lglcss.There is so m~~cllvariation in c.luttl1 silt ill 111;111y s~)~cicst11;tt I.CI)OI.IS 01 the number ol eggs lititl by si~lglcIc~~talcs or Ijy ;I Ic\dr intli\.itlrt;tls ;t~-egenel-ally without v;tlrle. Nevertlle- less thel-c ;trc ;~ljor~t50 str~tlicsol' clr~tcl~si/c or litter size that arc based on many intli\~itlrt;tls('l';tblc 2). T'lle (;ekkonitl;tc. ;rn(I 1'eiicl;te Ila\,e s~nallclt~tclles and the same may be true ol' thc I;r~-gc~.;rg;tlnitls. M'itllin the Igrl;tnitlae, in which more species Ila~eI~ecn sttttlietl, the c.lutch six \,;tries fl-o~none to 2'1 per fernale. Largcr spccics gc~ie~.;rlly1;ry 1nol.e eggs tha11 smaller ones, b11t exceptions in both tlirections (Plr~-yr7oso1rr,/ant1 Illrrm) occl~l..Vivil)aror~s spccies have sln;~llcr brootls t11;ln ovip;~~.o~rssj~ccies oS coml)arable sise. Finally, almost without exception, oltler ;111tl larger 1is;rl-(Is 11rot111c.elarger clutches than smaller, youngcr ones within tl~csrme s~~ecies. I think the extremes in c-lutcli si/e 211-e ])I-obably low known fol- 1is;lrds and actention slloultl be trrl-nctl to 111-etlictio~istllat nlay lje matlc from the av;~ilal)lcinforni;~tiol~. The first is that snl;~llc.ltttch si~emay indicate that ;I slxcies Iias incre;tsctl its I-cpl-otlt~c-tivel)ote~itial by rep~.otlucingmore often r;~tIicl-tIi;~n I)y inc.~.e;~singtlie nrl~nl~erol cggs per clu~cli,or th;rt it is a sl)ecics ill wI1ic.h mort;llity takes 1)l;~cerelatively late in life I-ather than vcry eal-ly. The mean clt~tclisi/c oS S(.clofiorlts grc~ciosrrsis low lor a Scr '1'11~CS(CII~II~ p;t[)c~.0). Illgel ;III~(;ree~~l)cl~ (I!l(i(i) (lit1 11ot appeal- r~~~tilthis III~II~II. scrip1 11;1tl gone to press". I \\.is11 lo tall attc,tltio~~I0 tllcil- [';I[)cI. I)ccat~scil cotlt;~ins;I !vc;\lth of tl;ct;t otl rc1~1-otluctionof tl-ol~ic;tlli/;~t-(Is. 1 IFE I\ND 1)I.hIOGRAl'IIY 01' llT,\ Figures ;ire incans u~ilcssotl~erwise notetl; v = vivil~iiroilhsl>ccics - - -- Age .it C:lutcll No. of Scc~lo/~ovrrsjcrr-~-or~i (v.) 10 Src~lo/~orirstrrrtllrln/tr.~ < I y1-, 7 .ii Srrlo/)ovrrs occidr1rln1i.s 2 yr. 13.7 (,;I. 30 1 I yr. 1 or 2 1 I. 83--!I3 111111. 5.0; 07-1 02 111111,7.5 1.5 },I-. 5.8 2 yr. 2.1 2 yr. 2.6 2 y I-. 2.8 < 1 yr. 4.2 C:liaptr~;ui ;111d ~~ll:l~~lll:lll(I1)(i4) III~II.2 hl:is\I~:~ll>II>CI I look (I!l(iO) C:h;imacleont irlac Chn~~rrrel(~ohohrieli (v.) Bristartl (l!)(i5) (:lrcr~~rnrlroOitcrrrrio11t.s (v.) Bustasd (l!)(i(i) ------~ ~-- -- - - ~ ~ ~ - --- :\gc ;I( (:IIIILI~ No. of SI)cc.ics h1l;tt. siw c.l~tLclrcs ilrcthol-ity I .;tccrtid;~c: I,(rc(~r1(6III 111 (11i.s 1.mrcrIn i1ivir1i.s 1.nce1In crgi1i.s I.flc/~?lil 7lilli/~/rl-/r(v.) hl. Smitlc (l!l51) 2-1 l ;\-\nguitl;~r Cc~-?-lco?rotrr.s III rr1Iiro1-i~~crttrs 110-125 ~ntn.(i-1.1: Pitch (1!)35) 125-145 111111, !)-I7 Gc.7-rl1o1ro1rr.scoc~rtrI(,rr.s (v.) 2-10 l;itcIi (1035) Al~gllisfr(rgi1is (v.) 7-8 M. S~ilitli(l!)5 I j A7lgrii.s I,-ngilis (v.) 12 1 Kollit~at(193-1) * In this family thcre are lilalry rc~~orts,~riost of the111 indicating that 2 eggs per fct~lalcis tlic r~sualclr~tcl~ sire in this fancily. Somc s1)ccics iliva~-iablypi-oduce only 2 eggs pcr clutcl~(l)utt;~, 194.1; C;lrul.c.h, 1962; Boyti, 1940; I11ger ;untl GI-ccnbCrg,1066). o~lslybrcctlilig species), br~tcycles near the equator have been Illore com- monly corre1;rted wit11 rainl';~ll (Wilhofl, 1963; C11apm;ln and Chapman, IOGil). In sollie specics (Willloft ancl Keiter, 1965) there is no obvious factor with whicli tlle existence of cycles car1 be correlated. h1;ryliew (l965b, l!)(i(icl, 19G(ib) Ilas made ;I point of correlating the 1.elxotIuctive success of sl)ccies of the genus Urns .cvitll the quantity of wi~lter1.ai11. He assumcs tli;tt the rainfall intlirectly iilfluences reproductive succcss tl~rougliits efl'cct on plant growtll ancl consecluent abundance of insects, tlie I'ootl sul)l~lyof ZJttrcl. Sornctinles thc corrclatio~lbetween r;~inl'all ant1 rel)rotluc.tive st~cccsswas exhibiteel by only one sex. In some months thc s;urlple siles were so sm;tll (as low as 3) that I doubt if they were representa- tive ol' thc ~.el>t.otluctive success of the polx~lationas a whole. Fin;rlly, in :I s1:ec'ies with overla1,ping age classes ;IS ill IJlnc~,clilrerent frequencies of ani- 111;rlsol' tlill'erent age cl;rsses might be p;rrtly responsible for his results. 'I'llc significance 01' l';rt storage to reproduction in reptiles needs further stutly ;IS tloes tlie lunction of the corpus Iutcum. As long ago as 1934, Rollinat st;~tetltli;~t the li/;~rtl1-crc.crtcl cigi1i.v ~)ossessedlarge fat bodies, particularly the fenlalcs, that were tlcl~leted(luring the first two ovlrla~ionseach season. I-Ie srrggcstetl tllat tlle lipitl in them nligllt be utilized for egg production. Other ;rulhors 1i;~veriotctl the inverse relationship between fat storage ancl vitclloge~~esis(D;rl.evsky, 1!)57; (:li:~p~n;tn and Chapman, 1964; Hodtlen- b;rch, I!)(ili). On the other h:rntl fat-body build-up has been reported to be c.oncul.1.ent with rel~rotl~~ction(Marsllall ant1 Hook, 1960) or to be scc~riirigly t1111.el:rtetl to tlie reprot111c.tivecycle (Bm-wick :uncl Bry;rnt, 1966). C-,ol~~o~.a . Illtea have bcerl recognizetl in every species of lizard ex;rrnined, ;~ntlsollie tletailetl strttlics of the structure and histological origins 11;rve I~eenm;~clc (\~\~cckcs, 193.1 ; Hoytl, 1940; blillel-, 195 1). Tl~el-eis ;it least one exl~erii~lc~it;~lstl~tly ol corl,lts lutel~mf~~nction (P:~nigel, 1956). 111 vivil~;uol~s lizartls tllc cot.l,~~slute~~~rl rct;rills an aplxlrently functional state until ne;w or after ~xr~.turitioll.In ovil);u.ous species, tlie corpus lute11m disappears soon ;~l'tel.ovil)ositioll, so that tllc n~~rnl)crof corpora lutca macroscopically visible in the ov;~rywill give no illdic;~tiollof ~llctotal nulilber of clutches ~)reviouslyIaitl. (1. ,Johnson (19fiO) reportccl that lutea from four previous c111tc.licswere ~llacrosc.ol,ic;lllyvisible in the ovaries of females (liolbroolcin I(,?ctrrrcl) 1;rte in [lie rcl,rotluc.tive seitson. 'I'liis rcporL neecls verification in;~sn~rtcl~;IS corpora atreticit arc easily confusccl with tlegener;rting corpora lu tea. l;ill;~lly,there are two c.11rio11src1)orts in tlie literature that tleserve brief tliscussio~i.ll~~st;~~-cl (l!)(i(i) intlicatetl that the oviducts oC some viviparous c.l~;rlr!clo~~sc.ot~r;ri~~ctl enil~l-yos of LWO very tlilferent si~es,suggesting the 1)ossibility 01' a secontl ovulation :und fertiliration tluring the course of preg- nirncy. 'l'llc secontl 1xipc1. is the oft-quoted one of Wooclbury and Woodbury (1 !)45) wit ic.I~ptrt.l)ot.ts to sllo~~tll;~t in Srrlopo~ir.~g.rr1rio.r7rs vi tellogenesis of ovitri;ttn follic.lcs oc.curs in the f;t11 and tl~;itthese parti;~llyyolked follicles 1.emai11 in ;I pre-ovulatory state until the following spring. This is the only t.cl,o~.tknown to lne of ~.etetltionof yolkecl follicles by 1iz;trds during the non- 1.elx.otluc.tive season, ;tltho~~ghthis phenonlenon certainly occurs in snakes. 'I'l~e exit( I ~volclsof \\'ooclb~~ryant1 \l\Tosdbury ;ire as follows: "lhring the st~rtlr~lcr;ttltl fall of otlc ye;tl-, tlepositiotl of yolk 011 eggs to be laid the I'ollo.cvit~gse;tsott I)eco~ncs;iI)I);trenc . . ." Itl;~smltclras their observations were nlict.osc.ol)ic., cvitlcnce of yolking might have been seen that is not macro- st.oljic;~llyvisible. I{ecattsc they tlo not state w11;rt follicle size is ;~ttainetlin tlre S;rll, I c.;tnttot jt~tlgethis 1,ossibility. It is l~ossible that the enlarged I'ollicles tlrcy s;tw in 1;ttc sttnlmet. were those of ;I second clutc11 to be laid tlrtr[ season. Tlley h;ttl no li/at,cls ;rvail;tl~lefro111 the winter, few from early sl)t.ir~g,:t~~tl c.ollcctiotl t1;ttcs ol' the latter are not given. Therefore, the yolked I'olliclcs secn it1 the S~I-ingcoultl 11;tve been yolked tllcrt spring rather tlr;tt1 tl~el,].cvio~~s 1';111. I'olkecl follic.les ;Ire present in fem;~leUtci strc?ish~iriancl in \vestcl.II C:olor;~tlo,1101 I';w fl-o~rlthe Woot1l)ttl-y's localities, in late RiI:irch ;~tltlc;~~.ly :\l)~-il, ;tntl these are known to have untlergone vitellogcnesis that sl)~ing.1Jt11il c.onfi~.n~;ttio~~ of this report is obtained 1 think it sllo~tltlnot bc c.itecl :IS ;In excel)tiot~;il~.el,rotlttctive type (see Miller, 1959). 1 1l;lvc s;iitl little ;tl,o~lt the ~.eproduc.tivecycle in mtle li~ards,in p;trt I)cc,;ruse 1 I1;tvc (lotre little work in this ;tl.ea ant1 partly 1)ecause it is of less itttcrcst 1'1.0111 111~'st;t~rdl~oint 01' pol1ltl;itio11 dy11;1111ics. AS a genel-ali~atiorl, 11t;11eli/;~~.tls it1 tI~cte1nl)er;tte ;lone unclcrgo sl)et,matogenesis in the fall, sl>c~.~niogc~lesisin the spring (l>utt>t,1944; Miller, 1959; Kchl and Cornbescot, 1!)55; H;rlr11, l!)ri,l; Goltlberg :untl Lowe, 1 9(i(i). On the other hand, two s1)ec.i~~111;ty ~;IVCcIif1e1-CIII cycles it1 the same ;u-c;t. Utn st(cnsbrrriann adliere to tile genet.;tli/;ttio~~:tbo\,e, but 7ir.ostr1rrri.sol-~i(rtrr.c in the same area emerge I'rotrl Ilil)ct.~~;ttionwith s~n;tlltestes which ral)itlly increase in size tluring [he sl)~-ing(:\sl'lr~nd ;tntl I,owe, I!)(i4). 111 the trol)ics, males may be in repro- clu(.tivc c.ot~tlitio~lit11 yc;tr wlrctl the fe~ll;tlesof the same species ;we clisti~lctlyc.yclic.. l,l'~l:l INC~II~,\l.lON AND (:I.sI..\L.ION TIMESKEPOR.I.ED FOR SEVERAL.SI'I~CIFS 01' LIIARDS All figures are clays unless otllcrwise indicated --- -- .~ Incubation or gestation tillre April-May, k = TO; May-Aug., x = 57 - x=43 Carperr tcr (I!)(;Ob) 48-58 C:rcrnsl~aw(ll155) 50-55 \Voodt)~~ryar~tt TVoodbut) (1945) S~.c~lo/)or-ri.scycl~?ogc*r~ys (v) Hunsaker (1050) (,'~o/(r/~l~y/riscollnris Fitcl~(I956h) 1.iolnr.111cis 111 r~ltifor~~iis(v) Pcarson (I 954) /'/~oli~lol~ol~i.s~t~o~~ii~iti~ Bustartl (1964) ca. 1 IIIO. Sexton et (11. (1063) 50 Cdglc (1 !150) Agc~~rrnclgnilia ca. 60 Harris (1964) -- x=53 Carpe~~tcr(l'J(jO1~) ca. 60 Fitclr (1958) 50-55 Bostic (I 966) Sci~lcitlae 1~11111etesjcr\r.itrl us ca. (i weeks Fitclr (1954) lrrt~~c,r.rssc~/~lrr~/~iorrnli.s x =46 Breckcnritlgc (15143) lircr~~rr.c,.soh.solc/rrs 5 1 Pitch (1955) ICri IIIOC~.~rgr-rgiris 51-51 Mourlt (1963) l.c.iolof)i.s~~~c~zr.1o11tlic.n (Y) 12 weeks 13arwick (1959) /,?I~O.\OIIULIrrlrr-trle 111i1n.4 weeks R. hf. Jolunson (I!153) /.?rgoco~titrl(rte~c11e 4-5 weeks Lewis (1951) l,;g(,r-~~i(irlt1171 itrg11(1111i (v) (i0-80 13:trwick ;trltl i\~~guitlac A 11gui.s frogilis (v) S;~~~tusiitl;tc. X(III/JI.\~(L71igili.s (v) se;~son;~lcollet.tion of lc~n;~lcsc.olitaining o\,itlucal eggs ;~ndthe tirne of ;~ppearzunccof Il;~tclilingsin the lieltl. Sonle of the avail;~l~leestimates are shown in rl';tl)le 8. 1;or ig~tanitls;tr~tl teiitls, 60 tl;~ysseem to be the irveritge inc~tbationlime ;und is seenlingly intlel)entlent of the six of the species or of its eggs. The short itit.~tb;~tio~ltinne ol' some skinks seems surp1-ising in view of the habitat occ~tl~ieclby ni;uny ol tl~e~n,bttt skinks nlay retain the eggs in tlie ovitluct for ;I c.onsitle~-;tblelinlc 1)etwccn ov~tl;~tion;IIICI ovil~osifion.This pllenolne- 11on 1~1s11eeti tlen~o~~st~~:~tecliii l-(li,<,~/(l ttir~r(!/i.s ((:ool~er, l9(j5), ~vllicl~evi- dently ret;tins its eggs ill the ~\~itl~rc.tfor ;tlxjnt ;I n~ontlnfollowing fei.tili- z;ltion. The reco~.tlitl(.~tlxltioti tinle 01 216 (lilys lor 1'l~olitlobol~r.s(Htlst;lrd, ll)(i'l) w;ts tleterniinetl ill tllc l;tl~o~.;lto~yat 80-!)O0 F tlu~.irigthe tl;~y,(iOU 1: at night. 3'his sl)ecics is ;I high-;lltit~ltlctciitl lro~nEc~~;~tlot- and n1;1y ~~;IVC ;I long incubatioln titile ~lntlerII;ILLII.;I~ (.~n(litio~is. Vivip;l~.oc~sspet.ies ger~er;tlly1.ecj1li1.c 2 fo .3 ~nonthsI'or gest;ttior~; tlic longest rccoi.tl is 5 nio~itlrsill the ~nontancI~iol(rotrlr.s (I'earson, 1954) in Peru. As notctl l~i~evio~~sly,tile ~ninimrnn gestation time for vivil);t~.ot~s sl'ecies is ;tbout the sxne ;IS the tinle 1.ccl11iretl for some oviparous sj~cciesto ~)ro(lucc2 to 3 cl~~tcl~es,so nl~lltil)le cl~ttt.lnes in these vivil~;u.ousspecies, most of wllic.11 oc.t~tpyli;tl)it;~ts with stl.ol~gse;~son;~lity, seen1 out of the '1'1~rl.:01: 1~1'1'1.~\l<~i~(:l~.--'~~l~es:lt.t time ;it wlliel1 1latt.hling utas first al~l>c;~etlin tllc Iieltl I\~;IS c;u.efr~llynotetl each year ;untl these cl;ttes ;Ire showil below: only ;I tlill'erel~ccof :111o~tttwo weeks cxisls in ~lieeal-liest appearance over tliesc (iye2u.s. One ol the ;~tlv;unt;~gcsof C;IL storage IV;IS 1)ostulated to be its ;tssur;ulce of early reprotluction for the li~;u.tlant1 subsequent ex-ly hatching of its yoiuig. Lizards t11;tt Ilatch early will a11 nl;~t~trein tiine to breetl maximally the followitig season, i.e., they will Iiave become mature long before the onsct of the t.cp~.otlur.fivcse;tsoll. Fot. this l.e;l.son, I tlio~lghtthel-e might be 1.11.1: AN11 DEMOGKAPIIY OF lJTA 3 3 an advantage accruing to early hatching lizartls, and i have compiled data on the proportion of the adult population each year that was comprised by lizards hatching early ;~ntllate the previol~syear. These tlata lor the years 1961-1964 are shown lor those lizartls that were 23 mm or less snout-~ientat the time they were originally marked (7'able 4). 'I'he lizartls appe;lr to be reprcsentecl in the breeding population in itbout the s;tme freqclcncy in which they are hatched. There is a slight bias f;~vorii~gtliose l~atcllingin late July; llowcver, these clat;~do not suggest an Ti~rrcof Ir;~lcl~ing -- JIIIIC 1-15 June Ifi-30 July 1-15 ,lr~lyI(;-31 Atlg. 1-15 ,411~.1 fi-3 1 Scpl. 1-15 S?[)t. I(;-:jo OCL.I -I5 at1v;rnt:tge to early Ii;~tching,1)rovitlctl the lizartls hatch prior to mid-August. IJntil this (late tllcre is still ;I s~tflicierlrlylong growing season to insure that lrlost oS the you~~gwill rnature in time to reproduce early the lollo~iing sl~ring.Fol. tl~oschatching irl 1;ite ilugust, rn;rtl~ri(ywill be tlelayetl lintil so~netimethe l'ollowi~tgs1)ring or sun1111cr-,so tllry will I)e at a r-el,ro(luctive (;ISwell as ;l soci;tl) tlis:rtlv;tr~t;rge comparctl wit11 lizartls h;~tc.hingearlier. The tl;rta on tirnc 01' ;\ppearanc.c of llatclllings lor the years 1961-63 ;Ire sl~ow~lin 1;igur.e 3. These three years were cl~osenbcc;iuse in then1 we c:oncentr;ttetl upon getting ;ill li;ra~(1s m;~rketl;IS near their time of hatclling ;IS ~~ossiibe.As this figure sl~ows,it ~iollltli~e irnpossiblc to (letermine the nurnl)er of' c.1~1tchesrcl)resentetl. 'i'11e1-e ;Ire no tlistinct peaks because all of tl~clemales (lo not 1;ty eggs ;ti the same timc, the tlevelopmental rate of the eggs is ~~resu~n;~blyv;u-iable, ant1 some late-rn;rtrrring fe~rlalesare laying a first clutch concommitant wit11 the secontl c.lrltcll of othcr females. 15 JUNE 23 1 JULY 9 17 25 2 AUC 10 1;lc. 3. Til~~eof ;ippearancc of hatclrling utas OII 2 Trxas stntly areas, l9(il-G3. Althoug-lr 1r;r~clrlilrgs:rl~r~caretl ;IS 1;ite ;IS r;~rlyOctol,cl., the 1>roportio11hatching ;~fterinid- Augusl was r~egligil>le;IIICI was o~llitted froill the fig111.c.Tire ortlilrate shows tile total ~~~llnbcrrccordt~l 011 CLICJI date. Srzl:. ANI) I\PPEAIZANC:E OF ~IATCHLINGU~~s.-Utas at hatching have an open yolk sac scar ant1 a semi-transparent abdominal wall. Tlle scar closes rapidly and the body wall quickly becomes opaque, for it is unusual to C;IIICLI~C i~ liz;~rtIwith an open scar or transparent abclomen. Only 17 young were captllretl while the yolk sac scar was still open; the srn;tllest of thcsc was 18 lnln arid the largesl 23 rnrn. lhe mean size at hatching is 22 lllrrl (0.3 g~n),but tl~rouglloutthis study 1 have consitleretl any 1iz:irtl of 23 Inin oi- less a recent hatchling, ant1 ha\re tlesignatetl the time of first captul-e of 1izard:j this size as the (late of Iiatcl~ing. ?'he sexes ;11-e similar at li;~tching.I3otl1 are distinctly sti.ipet1, :inti the sl~ottitigc11ar:icteristi of oltler males is not fully tleveloperl (Pl. I I). By the tirne the lizartls I~a\.egi-o.czyn to a snout-vent length of 33 niln, the sexes arc Pl1otogral)lrs of fct~~alc-(Icft) and 111:ilcutas. 7'lic sl~lallcr;inilllnls arc a week or so old, tl~c1ar.g~~ ones scvcral w~eksof agc. 'Tlic s1)otting cll;irartcristic- of tlic atl~llltnalc can I,c sc.cbn in sotl~c.of t11c. j~~cc~~ilc..;sllowrl. I'lloto I,! C:l~arlcsMcKinnc.~. c~le;~rlytlistingilis1i;rble on the basis of 1,;ittel.n. The fe~iialeretains the stripetl ji~ven;\lpattern, but this is alteretl in the nl:~le by the al>l>eai-anceof blue spots on tlie back ant1 tail. Until this time, males can always be tlistinguishetl by a 11;ii1- of enlarged scales just posterior to tlie clo;~caat the tail base. 1%). the ;ige of H to 10 weeks ;it ;I six of 35-'10 rnln. some males tlevelol) ;~c.tivcI'einor;~l poi.es, ;inti most males develol, them prior to their first winter ;11it1 well 1)eSol.c the onset of tile I,~.eetling season. These st]-llctures may be I IFF. AND 1)EMOGRAPIIY OF IJl'A 3 7 I.cc;Iptures the sirmc intlivitlual night be a member of two different sire classes, or the captures might fall in two tliflerent seasons. In either event use oC sucll cl;~ta uloulcl PI-eclucle accurate t1etermin;rtion ol variations in gi-owtll at din'erent si~esand seasons. I tirst analyzed separately the d;rta lor different years irnd tlitferent study ;~rc;rs,hut I 11;1\~shown only the significant tliffcrences in the c.oinpilation. Only data lor the years 19(il-I9(iS, whe11 intensive e1for.t~were ~natleto rec.al1t111-cjrl\,eniles I'rec~uently,were nsetl in this section. <;RO\YTII 01;~IAT(;FII.IN(;s.-~'~~~ grou~tll of liatchlings is at lirst cjuitc slow. IVIucll ol' thcir rnai~lten;rnceencrgy clr~ringthe first few tli~ysol' their lice may be tlerivctl fi-on1 yolk remaining after hatching. T11e growth rate of I~;rtchlingsbetween 20 ;rntl 29 irlnl S~IOIIL-ventis signific;r~ltlySIUWCI- tllan those 24-34 nun, esl)cci;llly in the tern;rles (Table 5). 'T'hcrc is ~I-;I(tic;llly no cliffel-encc in the cI;~ilyrate of g1.ou1t111'1-om .June lo Scl)lcmlIcl-, tluring which pc~.iotl4 18 malcs incrc;rsetl in lrngth at :I Ixtc oC .22 111111 per tl;ry ;111(1 4!)(i fenl;lles ;I( .I9 n1ni 11e1-tI;ry. ASS~III~~I~~;I stcatly grou~tl~;kt this 111c;rn incre~ncnt,;11q11.oxirn;rtely 100 cl;~yswonltl he req~~iretl 1.01. :I rn:~le to re;rch ~n;rturityant1 105 clays 1.01. ;I l'cmalc. Tll~~s,110th scxcs sliol~ltlin:~turc within ~1 montl~salter hi~tching. 01lly ;I l'ew g~,owtll1.eco1-ds are ;rvail;rble lor the fall nlo~~ths,0ctol)el- ;~ntl Novc~uber.'I'hirty-lour. ni;~lesgrew 211 ;I rate of .I5 lnlrl per (1;ty (luring this periotl ;rnd 7'2 l'eirl;~lcsat :I rate of .1 1 mm. Tllercl'orc, eve11 clt~riilgthe late C;111 the r;rtc of g~.o~~tllis slou~~tl by less tli;rn one-1l:tlf the sumlrlcl- rirle. C;I I IFF ANI) DEMOGRAPHY OF llTA I),lll.~hi1 AN GROWTIIINCRE~~I$N 1.5 OF SUB~DIJI.~' AND :\I)UI.T U ShS OF THRFE5111: CI.ASSI:SIN I)IFI'I:RI:N~I.SEA.\ONS 1:igrlrcs in ~mrcnthcscs;trc the nl~nll~crsof rrcol-cls .~ ------. ------40-41) tnnl 15-54 n11ll 50-50 m111 - - - -~-- ~ - - 1);1tc M;tles Jc1111cs R.l;rlcs ~IIIIS M;tles 1;cm;rlcs ------~ IIII-,I~ .21 ( 2) .27 (21) .I0 ( 5) .X( 3) .I:!( !)) - I.St. .24 (15) -- .--~- .I7 ( 3) ------A - 0ct.-No\,. .I I (I!)) .Of (If) .08 (21) - -- - I)cc.-]:111. .02 ( 1) 0 ( 6) .05 ( 2) - .04 ( 3) - 1cl1.-Mar. .07 ( ,4) .(I5 (I I) .OS (I 2) .03 ( 3) ------ ,\l)~-iI-R.l:~y .O(i ( 3) .06 (2 I) 44 ( 7) .Oil (I 3) -- ~- - -- >. ON -1tII' SAhll ~l.111)~/\RIAS I'ig111-csit1 ~);rrentltrscs;trc IIIIIII~~I-sof rccol-tls. 1).,I~.I . .CII~ . ,111. fl-~IIItlie 111on1hsof JIIII~;untl July corrcl;~tionis with tlic total numbers ol' juveniles rcgisterctl on thc stl~tly arcas t111ringthe threc yeat-s: rl'lie inc~c;~setlgrowth rate in lY(i.3 came at a time when natality on both areas was higher than during the precetling year. Further, the number ol young registered on area I I was higher than in any PI-evious year. 10 tlONt\1 1) IV. II~NhLl i\ct~1;11tlat;~ on tle~~sityoI' jl~venilcsitr-e ;~\,;tilal)lelor June-,july of these three ye;rrs. These tl;~t;t are l,r-ol);rbly better th;rn tlle p~-e\,iotlsones ill that they cover ;I shorter 11e1.iotl ol' time tl~lring~v11ic.h most ju\:eniles ;tppcar in tllc pol)~rl;~tio~~;;11so, they show the ;tc.t11;11 n~l~rlbcrof young known to Ile on tllc area at that p;u titu1;u time: These tl;tt;~;~rc cor~sistcnt in in(lic;~ti~~~I~igllcr tlensitics (luring the periotl of i~lc~.c;~setlg1.owt11 rate. 'rliel-efore, it scelrls ~-e;~son;~l~leto conclucle tl~tttl~e I~igllc~ tlerlsity c.otrpletl with faster. growth intlicates an inc.re;~setl I'ood st~pl~ly;tntl l'trrtlle~.suggests that the l,ol,ul;~tion sire is ;tt 1c;rst lxlrti;~lly 1.cso~r1-cclin~itctl. 7'11e1.e is ohviotlsly 11111~11 intli\iitl~~;rlv;~~.i;~tion in g~.owtl~ rate t11;1t I Il;~venot tliscussetl in (letail. Solrlc ;tnirn;rls sl~ow~,~-;~ctic.;~lly no growtli ;IIICI otllers g1.0u1 ;I( 111o1.e t 11:111 twice tlie 1rle;tll I.;Ite. 7'11osc whose growth is r.et;l~.tletlmay I.C'I~I;I~I~ilnlll;itu~.c t11rot1gIlo11t the next breetling sc;rson; on tl~e o~l~cr11;1ncl, some ol' thc~se~-et;~l.tle(l intli\~itl~l;~ls a~ltltlcnly ;rsslllne an accclel-- ;~tctl1.;1tc ant1 III;I~re;~ch i~~attlrity rnitlway t111-oughthe ~.el~rotlucti\leseason. Howcve~.,it is much 1no1-e comlrlon for li/artls ol I-et;~rtletlgrowth to be e1imin;itetl I'ro111 tllc pop111:1tio11111.io1. to m;rturity, so th;~tby the ti~rleof the hl.c,ctling sc;lson ;11111ost2111 11t;ts ;>I-cill I-cl,~-otllrctivecontlition. (;rcow~rI or: \r'or~~c;IJ7t.i\s IN 1.111.. 1 ,ABORA.I.OKY.-()II Scptcnl1)el. I ti of one year, (i5 juver1;11 utas aver;lging 31 mm snor~t-ventwere 111-ought into the l;~l)ol-ato~.yant1 on Scl1ten11)er 21 a11 ;rtltlition;tl 15 wcl-e ;ttltletl to the g~.otrl>.l'l~c li~;~~-tls were fetl on fieltl-c:ollcctetl termites, l)rosophiln, and mc;llwo~-r~ls,at~tl m;tint;~inetl 1111tler tile c.o~l(litions tlisc-ussctl in the inti-otluc- tion. Sonle tl;tt;~pe~-tir~ent to tllis g1.owtI1 cxl~e~.ilriet~t;trc S~OWIII)elow: VIV;III Ic11gt11 ~,~C;IIIlc~~gr 11 hIc;111ICIIXIII ;!I SI;I1 t O(T. 30 I)(.(.. IS hl;~lc!, :i l 111111 (23) 3) 111111 (I!)) I;CIII;I~CS :!I III~I(IS) 37 111111 ( l I) I3 1n111 (25) 'I'llc ~n;~lcsaucr.e utili/etl I'or ;r~~olllel-pr~~'l)osc ;~ltel- O(.tol~er .30, but tl~~ringtl~e :~pl~roxi~rl;~tely .IO-tl;~y intc~.\.;tl of obscrv;~tion they grew :kt ;in ;Iverage 1.;rtc 01' .20 ~ninI)el' tl;~y.DLII-~II~ the s;111ie pel-io(l Fciil;~lesavei-;~getl .18. These arc ;rbout the ]-;Ices ol)st.rvetl in a~~i~n;~lsin the iicltl, int1ic:tting that the lizards untler n;~tu~.;llcontlitions arc p1-01~1blyapp~-o;~hi~lg their maxi- munl growtll l~otential. I;~.omOt.tol)c~. to I)c.c.c~t~l)c~.tile females ;~ver;lgetl.I2 111111 per clay, ;111tl the ln;~,joi-ityof tl~eirlreachetl the six of sexual rn;~lrlrityprior to the cntl of the experiment. 7'he l;~bo~.;ttoryg1.owt11 rates in fen~;~lesvarietl betwccn .02 ant1 .25 Inlu per clay, so they we]-c 110 less variable untlel. the ~~nifoi-nl1abo1-atory contli- tiol~s;~ntl contin~~o~~s foot1 sr~l)l)ly than they were in the feltl. There is no intlic;~tion that the gl-owtli I.;I tes in the labo~.;tto~-ywel-c f;~ste~-th;111 those in the lieltl. !\ S\lh~lh,fAl<~01: ~,I~~F.R~V~~IT C:(?AII>AR:\~I\I- GROIVIIIR j11.s (11: IN ~IXI1,rR I):\Y R~.rourmIN IIII: I,IT.F.RAT~JRF All I-atcs I-cfcl- to j~~vcl~;~lallillrals 11nlc.s~otherwise t~otctl -- -.~ . .. ~ ~ - - ..- - .- - - Sl~ccics (;rowtlr I-;rtc Ar~tl~ority -- -.- ~... Igu;r~~itl;~c Srrlofior-ti\ olir~nrc~ris Iht S~IIIIIII~I-..30 p ; .37 6 I$l;~ir(l!NiO) ~eintcl-,.O5 8 ant1 p 2nd SIII~IIICI-,.28 p ; .?I Src:lo/io~-11sorrirlr~t/c~li.c .I;, 2nd growing scsason Fitc11 (l!140) Scelo/)ort/,r t1?1(171/ci/11,r .2!)-..35; .O(i-. 1 :j, Zntl sc.;~so~l (:rc~~,slr;~ls(I 955) (~'ro/~~/i/~~~t~i,~e(111/1ri.~ 1 .00, jr~st;tftCr liatchit~g; 1itcI1(10561i) 42-52 mm, .71; 60-70 111111, 32; 71-80 mtll. .3O; 82-85 111111. .20 Ilo,~ili,\r~r.v~~il/cilri.\ 0.5 to 0.2 ~~ntil~~l;lturc 1li1-tli(I!)(iJ) Ag;1111itl;1c Ag(tu~(i(I~~III~I 0.2, 1st (iIII~II~IIS I 1;11-ris(I!l(i4) 'I'ciitl;~c* (~~rc~~~r~clo/iltorri.\.rr~.vli~1c~1/7i\ .05 -.O(i? l%cllis(l!Mi.f) (~II(~III~(/o/I/~oI~I~.\.s(~vli~~(~ct/ri,s .I5 8;.20 p (;;~rpc~lt(,r(1!15!1/1) (~~~e~~~itlo/~l~orrr.,.scrli~rc~trlro 0.5. in fast growi~lgI~:~t~l~lings; o~~e-l~;rlfthis rate 211tl seasol1 1;itcIi (l!l58) A ~~~c,irinq~itrrl~-ili~~cci/n 0.4 to 0.2. r~t~til~ll;~trrrc 11i1.tI1(l!l(i3) I .;rcci-t itlac I.(IC(,~/(Iflgili,r; 1,. YI~IJ~/I(II-(I .05, for flrht yt31. br. Sr11it11(1!151) Sci~~ci(l;r~ E~i~rrcsrc~,fn.rciot 11,s 35. SLIITIIIICI- l;itcl~(1954) I;IIIII(,~(>,\.~~~/~/CII/I~OII(I/~,\ ..3 I-37 1Irc.ckcnsitlgc (I !)4:l) Ilri~~t~~cc~.~ob.\ole/11.5 .30. I st 2 c;lso~~s 1it(.l1(l!155) I<~i~rrccr~s~gr('gi7is I (i (I;I~)~I-;I~OI-\) R,lorll~t(l!I(i3) I.c~iolo/ii.r~~~r~zc~ltr~rtlicri .I0 H;II-witk (1959) At~guitl;~c: A~ig~ii.\j~ngiliy "5 hl. St~~itl~(llI5l) X;rnt rlsiitl;~c. X(I!I / ti,\io 11igili.r .02 ! blillcr (1!151) <;ekko~~itl;~c FI(~~~~i(l(tr/?'/~i~~gflrl~o/i(.~ir) III;~~.0.61; at lc:~st0.2 until 111a1rlrc (;;iglc (1!14(j(1) 1-ecjuil-ed to I-eath rnatr~l-i~y.-1'llis p~.csumablymeans that sperics whirl1 do not inatr~rein one year sirnl~ly11;1ve shorter growing se;isons. Mowcvc~-,in certain ai-eas ~llatai-e ecologic.ally ~narginalfor li~artls(high mo~~ntains, New Zealand, British Isles) there ai-e indications that slour growth rates prev;iil ant1 result in t1el;iyetl maturity. Alrnost all arlthors have reportetl some growtlr in lirartls after scxr~;rl~naturity, l)lrt at a rate of about .O1 to .05 mm per clay. l'lierc are no very sig~lifica~itcliffcre~~ces reported in the literature between growth rates of malcs antl females, nor differences between rates of immalure li~artlsin their first or secontl growing seasons. However, seasonal tlin'el-ences i~igrcwth exist as tlernonstrated by Iny (1at;~on rltas. 1'0what extent seasolla1 tliff'erenccs in growtll 1-cflec-t diRerences in temper;rtiwe, pliotol~criod,01- ;rvailal~ility of loot1 is not known. Laboratory st~~tlieshave shown (Fox ant1 Dess;lues, 1957; Mayhew, 1!)65tr) that the :r~l~etitcs;~ntl loot1 intake of li~ardsarc in(:]-eased by lo~ig~~hotoperiotls, 21 Iact i~~tlicatetlby iny own experiments oT 11hotope1-iodic clfects in Utn. M;lyhew (1965~)stated that L)ipsostr~rl-~rstdo~:rmlis brought into the laboratory in the [;ill gsew f21scer untler the same label-;rtory conditions 111;111 individuals brougllt in (luring the Eollowing sumrncs. There was also all i~ldicatiorlt11;rt inc.:rntlesc.c~lt light was most stirn~~latingto growth I 11;111 il~fr;r-red.1;rc1111 his studies tl~ereis cert;rinly season to 1)elicvc thirt there was ;I real dilTel-enct betwee11 the I-;II~:, ol' gro~ltliill his two ex1)cri1ne1lts,I)II( it is ~~llfo~-tl~n;~te tlxrl ll~ccxl~c~-i~~~cnts wcse 1101 st:rstetl with ani~nillsol' tl~es;~lllc six. Tlic average le~~gtlrof his fall-collected lizal-(1s was abolr~65 niln cornpared with 80 lnrn in the summer gl-oup. T711trs, some oT the t1iKe1-ence in gl-owth rate tliat he obsel-vet1 might 1i;lve 1~cn;rcco~intable to clin'erenccs it1 the age oC the 1i~:rrtls. ~~J~:QIII~,NC:Y01..SIIF:I)DINC; IN J~IJKNAI, U~.,ls.-!\ phc~io~ne~io~lvesy likely rclatetl to growtli rate is the frequency 01' ectlysis ~~Iiich,in utas, as in tnatly liz;utls, oc.c.urs hy stages; the cntisc ski11 is not c;rst ;IS a unit. The fl-aying skin nlay cling to ;I li~artlfou ;I c.o~lsidcrabletime, iinparting ;r 91-otesc-jue ;I~~ICN'.;III~Cto the ;~nim;rl. 11 has I~centlifficlrlt ill ;(I1 st~rtlicsto obt;~i~~;rc.clrr;rlc tlat;~on shetltling 1'1-eq1re11c.ybecause irn intlivitlirirl is seltloln 1-ccirl)rlrred at precisely tllc time it is shctltling; also, it is most lr~llikclyto I,e caught at this tinie several ti~riesin sllccessio~~.In 1962 antl 1963 we m;~sketlall young lizards with a clot of paint, thc color of wliich was chi~ngetlat regular inter\.;lls with ~lotc l~eingmatle oS whether the original lxrint was still present. IVhen initially paintctl a yo111lgli~artl may Iiave just shetl or be i~bol~~to slletl. The c11;rnces of getting an intlivitlu;~l at either of ~hcactimes slioultl 11c cq11;11,so with large nlrriibers ol rcc.ortls the average tirnc between painting ant1 repainting shoultl apl,roximi~te the average time between shedding. For example, il a liziu-d shed on ,luly 10, but is not calrght ant1 repainted until July 12, and tllcn shccls ;tg;tin on 11rly 27, 1,111 is not c.;tr~ght;rntl I-ej~;ri~ltetlttntil Atrgr~st1, 17 tl;tys h;r\,e ;tctrr:tlly e1;tljsctl between slrccltlings wllerc-;IS I wolrltl h;~ve estim;r~etl20. On the othcl- Ir;tntl, il thc animal w;ts ~-el);rilltctlon l~rly15 ant1 ;1g:ti11OII Ar~grrst1, the inte~.v;tlI~etween shctltlings ~vol~ltlIr;i\,e beell r~ntlet.- estim;ttetl. -1'lresc u~rtlc~--:tncl o\~eresti~n;rtcs\.\fill ~~~-eu~rn;rblyIxtlanc-c if :I suflic.ient 1111n1l)cl-01' I-cc.ortls;ti.c ;t\r;iil;~l)lc. 7'hc m;ijol- we:~k~icsscsin lrly t1;it;r arc ill thc f;111, wintrl., ;inti spri11g whc~rtl;tily recon~~;tiss;tnc-col thr study :ue;rs was not possible. During thcsc 1)el-iotls :I li/;ll-tl 111;ty shetl its ski11 ant1 go 11111-ccoverctlfol- ;I long periotl of time. For these 1x1-iotls 2111 tl~tC;III be tletel-tni~lctlis the I'rcclr~e~lc-y~ritll which ;trl intli\~itIrt;rlw;rs I-cp;rintetl over 21 giver1 periotl of time. Hopefully, ;II ;tplx.oxirn:rtim of sllctltling I'reque~lc.ywas ol)t;ri~letlby this tcc.hniqur. 'I'llc tl;tt;t I'or ,ji~vcrt;rl11c;ts ;rl-e shown in 7';111le I)in wlricll the years ;tntl itreits h;rvc Ixcn c.oml)inetl ill tl~e;tl)senc-e ol any tlillerentcs I~etweentlleir~. 1)at;r were not irsctl il the rec-ortls betweell ~.cj):rintingovel-lapl)etl se;rsons; if six g~.olrl)sMJCI.~ o\,el.l;~pl)ecl, such observations wcl-c ~)l;tc.etlin o\m-l;tlq)ing silc c-1;rsscs wIlellc~,c~.possible to ~n;rsirni/crl~c l)l.ol)o~.tiorl of tlle cl:~ta ~li;rt c.oultl l,c ~rsetl. I3otl1 1n;11e ;111(lle111;tIc IIC;IS sllecl ;kt ;rl)out 3-week intet.\~;rlscIrr~-illg tllc srlmmel.. 'l'llc 5 1-cco1.tls01' tllc exact ~lu~nl~er01' tl:tys bctwce~rshetltlings \r;try 1.1-om7 to U (;rve~-;tgc15). 'l'he inc-1-easein le~rgthol ti~nc1)et~vccn sllctltli~lgs ill the ovcl.l;tl)l)ing si/c classcs (7';1ble 9) 1.esrtlts Sroln the ovei-l;rp into the ;~tlrlltc.l;rss, whic.lr slrctls less frcc~r~e~rtly.There :ire no ;tl)l):trent tlift'el-cnccs bclrvcc~ithe scxcs in shetltling Ircclrrenc.y, I~rrtI~ec.:iuse tllel-e is ;I sm;tll tliKe1.- encc in tllc gl-owth l.;rtc ol the sexcs it ~vo111tlI)c srr1-111.isingii' a tliffei.enc-c clitl not exist. My tecliniql~efor nle;isr~ri~rgtlre lreqlrc~lcyis probably too crude to detect ;I sm;~lltlifference betweeri sexes. The tl;~t;rlor- 1)otll sexes ill the 20-29-1n1n si~egt,o~tl) were combined to furnisll at1dition;rl c1ct:tils about sheclcling SI-eqr~encyin this group Tor which my clata ;ire strongest (Table 10). The mean interval between shedtlings is 22.1 days with ;I range ol 2-48. Tllc overall variation seems rela- tively slig.11~;the vari:unce is only 7.9 (lays ant1 tl~estand;~l.cl erroi- of the IKK;III only 0.5 clay. ~- -~ - - -- - ~ ------p~- -- Nun~l)c~.ol' (lays No. of I~ct\vec,~~piti~~ti~~p'i I~~tli\;itluals - - - - 0-2 2 :j-5 1 (i-R 0 9-1 1 If 12-14 27 15-1 7 25 18-20 35 21-25 53 2 l-2(i 3ti 27--20 25 :30--32 14 3:!-35 I (i 36 -38 I3 3!)-4 I 5 -12-14 2 45-47 0 I X-50 1 Ec:l)usls IN SIIIL\I)III.TANI) .L-\I)~II.I.U1-~s.-The tlat;~on these are shown ill T;11)le 1 I. No sigriilic:~~ltclilferei~ces exist between 1n;tles ;inti fenl;lles at ;III~se;rson. Tllc si/e gror~l>(10-1!) nlrn t.ont;rins some anim:~lstll;tt arc not yet scx~~;tllynl;lttll.c, so it is IIOL surl,~.isingt11;tt tlle slicclcling Srequency ill this gro1111tlitl not tliller. g~.c;rtly l'1.oln tl~tol' the juveniles. The s;umc was ;~lsotl.11~ oS gro~vtllr:rtc.s. l)tl~.i~rgtl~e l';111, 111e slletltling l'reclr~cncytlec.lir~cs to bout once every 5-6 wceks ;111cl ge~lcrally(.cases altogether tlt~i-i~igthe winter. Finding 1iz;trds in 111e c;~l.lysl)l,i~ig t11;lt retain p;til~tplaced on them the previous fall is 1101 tlncolnlnon. DIII.~II~the spl-il~g, slletltling becomes Inore f1-ecluenc :tg:~in at i~~tc~.\~;~lsof ;tl)o~~t 2 nlonths. :\s the ;t(lults go into the l~recdiugseason, the I'l,cque~~c,yis ';lg;tin il~c,~.c:tsctlto al)oul once a ~riontl~. Slletldi~~g1'1.ecl11ct1c.y is tlo~11)tlessly;I cor~.elatcoi' gro~vil~rate, for the 16 1)OhAl 1) \\'. TINKL I I';rstcst shetltling ~.;rtesare loltncl ill the [astest growing young, ant1 in juvenal li~:t~.tlscon~l);r~.etl with aclttlts. Even :urlong atll~ltsectlysis is frequent, intli- (.;tting tll;rt I.CIICW;I~ of the stl.;ttl~mcorneum is essential even in the absence ol signilic;tnt g~.owtlr.No c1;1t;r ;Ire ;t~~;til;tI~leon shetltling l'requency in the l;tbor;~tory. 1,ittle il~l'orm;ttionis ;r\,;rilable in the 1iter;tture on shedding frequency in lir;t~xls,in 1);u.t I~ec;tl~seit is dithcult to obtain, but also bec;u~seits i1nport;lnce is not i~nnlecli;ttelyol,viotts. Blair (1960) ol)t;tined tlntn for only the first 2 ~noltsof .S~.r,loparrrsoli-otrc.c,rl,s, \\~hicll cwne ;it ;[bout +week intervals. Little or no sl~etltlingocc.tlr~.etl ill the winter antl, surprisingly, adult li~ards sometin~csclitl not molt for :IS long ;IS :I year. Fitch (19560) reportetl that niolting in Cr.ottrplr?~t~tsc.olltrris oc.c~tl-1-etlat 2-3 week intei-vals between Il;rtching ;rntl thc first hibern;ttion, ;rnd at ;tbout %week intervals in the secontl growing season. R/I;rt~lre ;iclnlts shetl their skin at about 25-clay inter\~;tls. I;itc.ll (1958) ~-el,ol.tetl tllat no (,'trrttritlophorris sexli,tzentrls re- t;rinctl 1);rint after 28 tl;rys, s~~ggcsting.that this is the maximum time between slletltlings. 'l'llcsc cstinl;ttes ;trc3 in gel~el.;tl:rgI.eetnent lvith those presented on Lltas. H;rvi~tg;tl~.c;ttly 1)rctlic-let1 the tin~e~.ec]~til.ecl to re;rch :I rtl;ttul-e si/e, 1 I~LIS~now t~1r11;~ttention to ;rct~r;rl(1;rt;l 011 the age at ~naturity.Feinales re;~chscx~t;rl ~natrt~-ity ;~t ;I mini~nt~~nsix ol 42 mln, nlales at about 46 mm. Ol~\~io~lsly,li/;r~.tls ill the 11;rtll1.;11~)opltl;ttio~~ will re;rch these sires only ;I Sew niontlls ;tIte~.Il;rt(.l~ing, IILI~ will not rcl~rotlucei~ntil the l'011owi11g S~II.~II~ IVIICII they ;rvc.l.;rge ;rl)oltr !) nlontl~sof ;rge. Howevcr, I ;~IIjustified in consid- ering the age at maturity 21s the time when utas reach a mature size because we have sllown illat these will reprotluce in the laboratory prior to the normal breetling scason. 111 this section of the st~~tly,I have trsetl only ;ulinl;~lsavhose life l~istory W;IS Cairly co~nl,letelyknown. 1 1l;lve ~tsetlanimals that were less than 24 nlnl wllen first marked and llence probably in their first weck of life. I have taken their age at maturity to be the time between hatching and the recapture date on wliich they hat1 first ;~tt;iirietlmature size. Unfortunately, this technique will almost always ovcrestim:ttc thc timc requircd to mature. For example, a I'c~n;~lccaptilretl on Septeniber 29 was 39 nlnl ;IIICI on Octol~cr27 was 42 mln. October 27 is t;iken as her tl;ite of matnrity, but she lnay have reacllecl 42 111111 scvcral clays p~.eviously.If there avas a very long period between the last two c;~ptllrestllc data were not ~~sccl. TAl3Lli 12 '1.111,:NLI~IIWU 01: 1)~~s I ------~ - -- - .. - - .------. ------Sire (111111) N Males N Fctrlales ~ - ~ 2 1 +.) 1 13 ( 95-1 30) 5 151 (1 25-2.17) 22 13 I (is ( 94-3 20) 10 135 (101-245) 23 7 1 17 ( 70-1 43) 7 132 (102-151) PI 11 82 ( fil-125) ? 82 ( 61-106) Totals 3 3 125 ( (i1-329) 29 124 ( fil-2 17) - -- - .. ------~-- There are 33 males ant1 2!) females (Table 12) for wllich fairly cornl,lcte 1.ccortls indicate th;lt abotlt 4 tnontlls are required to reach maturity. The period to ni;it~ll-ityin 1i~al.clswith rct;~rtletlg1-owth r;~ngetlto almost ;I ycar in males ;irlcl to eight 111ontl1sin lenl:~les. At least it is clear that alnlost ;ill utas Ilatching in the summer crrlr rc;~chscx11;tl maturity in the fall or c;lrly wintc~.,well ;111e;tcl of the breeding season. As notecl previously this is j,rob;~bly of great iml)ort;~nc.cin ;illowing spcrrn:~togenesis to 11roc:eed in tllese young 111;1les to the sl~crmatitlst:lge prior to tlie beginning of tlle relxoductivc se;isorl. In fenl;lles, attainment of m;~turity in the fall is imlx)~.t;intto ;illow f:tt storag-e. ,\ I)IS(:IISSION01; 1.111: I.IT~~:RATIII:~ * 111 :I ]1:11)(,rIII:I( ;11)])~:1rc(l:tfl(,r this ~vc~illo 11rcss, Y\v(.if(,l ;111(l I .(I\VC, I Oli(j ( \,,l(.l.. kltls. No\ir;~lc.\,No. 2247) ~)~-csc~itctltl:~la ~c~itlilrglo co11li1111hIillci's c~ti~~li~lcs. In lhe period 19(il-63 lizarcls were generally weiglled at each capture, not only to obtain clata on weight gain during ontogeny, but also to chart the change in weigllt 01' adults ;it dilf'erent seasons ancl to compilc data uselul for estinlating biomass. The data for each year and area were separately ;inalyzetl, but ilierc were no significant differences so the data were pooled lor discnssion. l'llc weigllis of juvcnal 1iz;rrcls at eacll 1 nlm sno~~t-vcntlength are shown in Table 13. Evitl~rltlylittle weight is gainetl during the first few - - ~ - --- .:ro ( 9) - .so (67) - .3f1 (I 05) /4l ( 1 ) .42 ( 5) 39 (113) 38 ( I) .4!) ( 2) - -- 4 I (2) -- .51 ( 1) - .51 (88) .55 ( 6) .5!)( 5) -- .50 (86) .55 ( 4) .77 ( li) --- .67 (74) .SO ( 5) .72 ( 5) 72 (i) .SO (I I) .87 ( 0) -- .7!) (68) .<)I( 5) l.on( 4) --- .S8 (64) I .Ol ( !)) 1.19 ( !I) ---- I .o0 (39) I .07 (I 8) 1.15 ( 0) l..5,l ( I) 1.10 (40) 1.32 (I I) 1.29 ( 8) I.38( 4) 1.14(20) 1.25 (17) I .40 (l(i) -- 1.25 (I I) 1.39 (2 I) 1.54 ( 5) 1.7( I) 1.37 ( i) 1.53 (28) 1.69 (12) I!( I) 1.( I) I .(in (219 1.73 ( 0) l .(i7 ( 2) l .(i7 ( 3) I .K1 ('29) 1.95 (I I) -- 1.88 ( 3) 1.01 (-11) 2.12 (17) 2.25( 1) l.98( 1) 2.13(30) 2.29 (21) 2.35 ( 3) 2.50 ( 1) 2.33 (39) 2.50 (20) 2.54( 1) - 2.47 (26) 2.48 (15) 2.50 ( 2) 2.91 (22) 2.76 ( 2) 3.00 (13) 3.34 ( 4) tl;tys ol' life: the tl;tt;r on g~.owtliintlic.;ttetl little or no elongation of' the ;~ninl;tl tI~t~.i~igthe S;IIII~ 1,el.iotl. Aftel. tl~efi1.s~ lew days oC life weight inc~.e;~scs~.;tl,itlly, tlot~l)ling al)p~.oxinlatcly every ~rlontlltluring the summer ;tntl e;u.ly l';111. Although sir~~~l)lcs;~rcstrl;~ll l'or ;I I'ew six gt.oups they indicate tI1;~t both sexes ;Ire somew11;tt 11e;tviel- in the la11 than in the sl~ringor sulnrncl.. It is tl~rringthe 1';111 tll;tt the 111;1t11ringLII;IS begin co store fat, :uncl I ;tssl~ntctlris is the sorl1.c.e ol' the increaseti weight. The information on jt~\,or~ilcsill tlle winte~.;rntl sl)t.ing is nle;tgc~-,p:u-tly 1jec.ausc I ha\,e littlc (I;IL;I ;~\,;~il;tl)lefro111 tl~cscse;tsolls ;tntl p;t~.tlyI,ec.;~~lsc ;ilulost all utas have ~.c:tc.l~etl;ttl111~ six by this time. Howevc~.,even tl~cseli~rlited cl;tca show c.le;t~,lytl1;tt t1le1.e is no sigt~ilic.;tntweight ch;tnge (luring the winter or ct;u.ly sl)~.ing.7'his ~,vo~tltlnot I)e ~)ossil)leil' the liyit~~tlswere tlepentling upon sto~.ctlenergy ~.esc~.vcst1111.ing the winter ;tntl e;trly slx'ing. '1-hey ;u.e active (luring tllese se;tsons ~vlleneve~.it is s~rllic.ientlyw;um ;t11c1 food is ;t\l;til;tble, ;IS inclic.;ttetl Ily tllo 1'1111 stonl;tclls of li~artlsc.ollectet1 ;it these times. Because ol tllc low ternper;ttilres prev;tiling, activity can probably be purchased at relatively little cost in energy wliic.ll (.;in, ill turn, be obtainecl by feeding tl11.o~lghtl~c c.ool 111onths. 13y this conrin~~etl;tctivity the ~~t;ts;Ire able to take ;~tlvi~ntagcol' ;in otlle~.wisc ~lttl';t\~orablcse;rson to continue growth, ;tltl~ough;it it sloav ritte. 1t is ol more t1i;rn passing interest, I think, that utas ;trc tllc only 1i;l;trtls ill thc ;t~.c;ttll;tt ;ue ever see11 tluring the winter inonths. If tlie 111e;tn weigllt is plottetl ;~g;tinstsnout-vent length, a I-enlark;tbly u11ilor111I.~KI.CSS~~I~ is oljt;~inc(I (1;ig. 'I), but the c.ur\,e h;ts less slope with ;ttlv;tncing six tll;tn it ([oes initii~lly.11' these s;tine weigl~tdata ;ire plottetl ;tg;tinst tile averaxc age ol' li~itrtls;it the tlifl'erent snout-vent Icngths, a true t.;tte c.tl1.ve ~n;~ybe obt;~inetl(Fig. 5). An obvious tlecrcase in the rate of growtl~occwrs its the li/;ti.tls ;tl)l)~.o;tcl~nl;ttrlrc six. 1;enl;tles al,pe;tr to reclttirc slightly mo1.e litr~cto ~.c:tch the s;une weight ;is tlie ni;tlcs, but there is prac- tic-ally no tlilfcrenc.e in tl~etile;tn weight l~etweeii1n;lles ;tntl fem;~lesof' the s:ttne length. I.ikc all ~~reviotrsd;~ta there is wide v;rri;~tio~~;Inlong inclividu;tls in rate of weight gain. '17h;tt tlle li/;utls c.hange shape wit11 ;rge is clearly intlic;ttecl. Sub;tclt~ltsI~iive ;I 1rlol.e elongate apl)c;tl.;lnce tll;tn oltler ;tni~rt;tls of the s;trnc length. l'llc wcigl~ts01' ;ltlulc ut;ts ;tve sl~ownill '1;tl)lc 1-1. 'l'liese tl;tt;t m;tkc c.le;tr tll;tt jt~ven;tlli/;t~.tls 1latc.hetl in one sunllncl- rc;tcli an ;~\~c~,;lgcweight by 1';111 t11;tt overl;tl)s t11;tt ol' tl~e~,;trerrt;tl c.l;tss (colnlxt~.cT;rblcs 13 ;tntl 14). T1le1.c- I'o~r,wcixl~t, like si/c, is ;I poor c.~.ite~.io~lfo~. sel~;tr;~ting agc c,l;~sses.Tl~c weights of ;t(lr~lt~ti;tles ;tncl fcrn;tles ;tl.c ;tbo~~ttlre S;tIKlC if li/;trtls of' the s;ume le11gr11;11.c co~nl)it~.etl.Ho\veve~., tn;tles reac.11 ;I greater lengtl~111;tri I'CIII~IICS, so the ;t\~el-;tgc~vcigl~c l'o~. ;~ll ;tclulr n~alesis ;tl)o[it one gr;ttlt g~.e;tce~.tll;~~~ 1ll;lt KOl. ;ttI111t Ic1n;lles. E'Ic. I. Correlation of weight ill granis (at,sciss:~) wit11 snout-vent length in tnillirlletcrs (01-di~~;~te).Solid circles, niales; open circles, fr~~~ales.Each point on the curve is tllc mean for a large- nu~ul,el.of rccortls. Tlle weiglit data lor each adult si~cclass in the summer and fall indi- c.ate that the lizartls are slightly heavier i11 the fall, but the overall means lor all atlults of all sizes for these two scasolls are not significantly different. l-lahn and Tinkle (19(i5) showed that utas utilize their stored Sat reserves ill tlie spring tluririg tlie initial estrous cycle. These adults and maturing young of tlic same year do not replenisli the depleted Cat reserves until fall, at thc entl ol thc reproductive season. These authors also showed that fat storage ill fenlales was greater tha11 in males. The data presented here clo not show a greater weight gain by females than males during the fall, but because thc tlifl'erence in fat storage between the two sexes amounts to only 2 per cent ol the body weight it would bc difficult to demonstrate a clifferellce in weight between the two sexes without extremely large samples. 111 adults of both sexes the greatest average weights are attained in the spring. 7'11e reasons for this are clear in the case of l'eni;tles in wl1ic.11 the bcgintling of rel~rotluction ;~ntl :tttentlant enlargenlent ol ov;ti-ian eggs 1xoduces weight increase. In both sexes, too, ~tnilnalsthat (lid not re;tcll nlatul-c six tllc 1,revious fa11 ;~g.aitlbegin to grow r;~l)itllyill le~lgth;tnd wcigllt; ~iiales,in ~~~rticul;~~~,double their weight alter ~nininlunlsix at ~r~;tt~t~.ityis attained. 7';tblc 1.1 ;~lsosl~ows th;tt tlie 1ne;tn weights ol' itninlals of tllc same lettgtlt ;I( clill'erent se;tsorls ;u.e 11ot g~.e;ttly tlillererit. 'I'he sm;tllest me;un I:I(.. 5. C:o~~clalio~~of weigl~l wirlr age for lirsl X wccks of litc for ll~oacli~iwcls tl~al wcw ~~r;trkctl;II hatclli~~g.Solicl circles, 111;tlcs; o1)clt circles, fc~~r;~lcs.Each point on tlre ,(.III.VC is tl~eIIIC;III of ;t li~rgcII~IIII~~I. of records. AI)sciss;~,weight ill grams; ortlinatc, tl;tys since I~atcl~i~~g. wcigllt l'or ~rl;tlcs(Scpt-Nov.) tlifFel.s fron~the greatest (R/l;trcll-May) by only .83 gl.;t~nor allout 20 per cent of the mean body wcight. In females the cor~.csljondingdifference is only 37 gram. Despite these similarities, I think it is not tlillicult to tliscet.11 rh;t~spring weights in nlales :u~dfe~nales ;Ire ;tlways gl.e;tter L~I;III SII~I~~IIC~weights for e;tcll si/c group ex;~~llined.The t1ilFercnc.e is ;~ttrib~tt;~blcto tile inci~casetl ;tctivity in summer ;111d the ir~c~~c>tsi~igte~nper;tt~~rcs tlt;tt rcs~tlr in higlici- energy cxpendit~tresant1 ;t consecluent loss ol weight 1)y 1rl;lny of the li~;~t,cls.Tllcrefore, to the concl11- sions ol 11;11111 ;~ndTinkle (l!)(i5) th;tt fat is in~pol.~;tt~tto e;trly rc'~)rotluc.tiot~ TABLE 14 \VFI(,HIS OF Anl1l.T MALEAND FE~~ALEIJTAS AT FOURL)IFFERENT SEASONS PRO51 Ml~lhl~hlSIZE AT MA.I.URITY70 M~~~hlllhlSIZE RECORDED Ikcin~alfigul-es arc Incan weights in grams; ligr~rcsin parcnthcses arc nt~mbcrsof records Snorll- Males Fc.111a1cs \,('Ill - - ~ - - .- ,,,,,,Jr~nc-Aug.Scpt.-Nov. Mar.-May Dee.-Feb. Junc-Al~g.S..l)t.-Nov. 1)ec.-Icb. Mar.-May - - - 42 -- 2.(i.3 (22) 2.64 (IS) 2.76 (11) 43 2.44 ( 2) 2.87 (15) 2.88 ( 8) 3.25 (29) 4-1 3.10 ( 9) 3.17 (12) 3.30 ( 3) 3.27 (24) 4 5 2.93 (23) 3.22 (1 1) 2.!l2 ( I) 5.65 (21) 4ii 3:11(4) 3.30(27) 3.(;5(2) 3.72(5) 3.41(28) 3.51(0) 3.57(4) 3.65('26) 47 3.68 ( 2) 3.86 (20) 3.96 ( 5) 4.14 (12) 5.56 (19) 3.45 ( 5) 4.07 ( 4) 3.98 (19) 48 3.45 ( 6) 4.18 (18) 4.24 ( 6) 4.20 ( 8) 3.52 (1 1) 4.01 ( 3) :1.!)5 ( 2) 4.05 (15) 4,) 4.08 ( !)) 4.31) (16) 4.78 ( It) 4.57 (1 1) 4.21 ( 4) 4.17 ( 2) - 3.00 ( 8) 50 4.34 (17) 4.88 (14) 4.54 ( 7) 4.91 (24) 4.40 ( 4) 4.80 ( 1) 4.1 1 ( 1) 4.30 ( 7) 5 4.(i3(14) 4.88(Xi) 1.65(4) 5.02fLI) 4.41(1) -- --- 4 .Xi<)( 2) 52 1.80 (13) 5.11 ( 8) 5.46 ( 8) 5.27 (16) ------4.17 ( 1) 53 5.02 ( 8) 5.54 ( 3) 5.75 ( 8) 5.48 (17) - -- - 5.27 ( 2) 54 5.1!) ( 2) 5.48 ( (i) 5.41 ( 2) 5.24 ( !)) 55 5.63 ( 2) 5.83 ( 3) 6.03 ( 4) 6.1" 7) 56 6.07 ( 1) -- -- 5.86 ( 1) 57 -- -- 2) x's 4.41 (XI) .l.l,l (138) '1.58 (511) 1.!l7 (140) 3.37 (102) 3.28 (58) 3.4 1 (23) 3.65 (173) must bc atltletl tllc contention that the fat reserve is also partly used in the incrcasctl nlct:~l)olic ;I( tivity in the S~I-ing. For all ~,r;~c~ic;~l]~~rrlx~scs there arc no tl;tt;~oF v;~luein the literalr~re011 the w~cightgains ol lirards under 1l;r111ral contlitions. For obvious reasons s11c11tl;~ta are 01. will I,c v;~lrl;~blefor estimating biomass, protluc.ti\lity, ;uld energy flow, ;II~([ more attention shoultl I)e tlevotctl to obtaining s11c:ll data in l'uturc stutlies of the na~uralhistory ol lizards. - I he tail is ;III org;~~~01' very grcat imj,ort;incc ill lirartls in such tliverse ;ictivirics as la(. storage, preclator escape, mating, and territoriality. For these reasoils wc llavc spc~~tconsider;~ble elfort studying the growth ant1 regencra- tion of this organ. The stutly ol tail growth presentetl the same problerns ;IS those encoun- tcretl by the study of I~odygrowth, viz., the clilficulty of recapturing the lirartl more than once while it was in the same size class and season. Many tl;~tawere discartletl that cut across more than one size class or season, but sl~llicientclata remain for sorne definite conclusions. 'I'lic ratio of tail Icngtll to snot~t-ventlengtll varies froin about 1.5 to 1.7 in females, frorn 1.5 to 1.8 in males. li the mean tail length at each snout-vent length is graphed, a nearly straight line is formed in males. In females ;I change in the slope occul-s at about the time of sexual maturity (Fig. G). The tail obviously grows at a fastel- r;itc than the body for the ratio ol tail lcngth to body length c11:inges from about 1.5 at hatching to 1.7 or higher at nlaturity. The actual rate of growth oT the tail h;is been studied by choosing data Iroin those ;iinorig our lizartls that never sustained a broken tail during their life. Only those records in which tail measurements were made at lcast 10 days apart were usecl. Data froin the two stlidy areas were analyzed h- -T,-.--T---.-- 7-r- -I-- - 0 10 20 30 40 50 60 70 80 90 100 FIG. 6. Length of tail (abscissa) plotted against snout-vent length (ordinate). Solid circles, females; o[>en cil.clcs, ttralcs. All figures in 1nilli1nctc1-s. scp;ii-atcly, br~ttllcl-c were no sig~tific.;~nttlifferences; ciala for tlilferetit years were not ;~nalyzetlsep;lrately. i\lmost a11 ol the ;~vailabledata ;Ire from the s~~mmci-months bec;r~~scour reca]>tlll-e efforts wel-c c.o~lcentr;rLetl at thirt se;rson (Table 15). Tllcl-c is :I statistic.;rlly sig1iilic:tnt tlillci-cncc in the growtll rate oC the tail I~ctwecnmirles ;~ntlfem:iles. Over ;un entire silnimcr this 111-otlutcsit tail about 10 ti1111 longer in the m:~let11;111 in the Senl;~lc. Iktween the two size gror~psconsideretl there was no significant tlin'erence in rille ol tail growth for either sex. In el1cc.t the t;ril grows at a (:onstant daily increment until bout the ti~neof sex11;11~i~atl~rity, ant1 this is t.efkctetl in 1:igurc 6, whicli shows the rcl;tti\,c const;uncy of the tail lcngtll to I~otly length I-atio in ,juve11:11rlt;ts. SV~I.-No\,. .Xi ( 3) .:is ('LO) 20 ( 3) .Is (13) 1)rli.ing tlic fall tlic I-ate of tail g~-o~ltllslows 10 ;~bo~rton~-li:~lI' tll:~t of thc s~~~nrncl-evcll when li/;u.tls ol' the S;IIIIC length ill the two seasons arc c.o~nl~:tk'ul.(;rowtll of tlic tail ~)t.ac.tic.;~llytc;lses tlrlring tlle winter, for ~vhi(.I~I II;IVC very l'cw ~.cc.ortls,Ixrt i~~c~.e;~ses;rg;~in in the c;~rlyspi.ing :it ;I rate not g~.c;~tlytlif1c1-ent I'rotn that in tl~eprcviotls l;111. Aclult 1iz;11-tlsIiave been tlivitletl illto two silt c.l;~sscsto tlctcl-mine tlle rate ol' tail growth ;ri'ter sexn;rl rn;~turity(*I':rble 16). ;\s with g~.owthol' tllc botly, g~.owthof the tail is slow aftel- scx11;11 1n;iturity; the rate seltlo~n cxceetls .O5 mnl 11cr tl;~y.At first g1anc.e the tl;lt;r lor atlrllts may scetn odd I)ec.;111semales 4(i-50 nim long h;~ve:I signific.antly faster rate of gi-0~1thin tllc fall than ill the s111nnic1-.71'l~is is rcatlily r~nclerst:~ncl;rbIcif one I-cmcm- I)el-s th;rt ;I liz;~r(lof this size in ~J~rnc,Jl~ly, or AII~IIS~is ;11jorit ;i ye;~rold, u~hilein Scptetnber, October, 01- November most of the recol-ds are for animals hatchetl in the summer ol that year, ant1 therefore only a few months old. The diffet-ence in rates is attributable to the differences in the ;Iges of the :tniln;~lsconi111-isi~ig the sa~liplcsI'ronl the two S~;ISOIIS.'l'his is true bec;~use01' the faster absolr~tegl.owth I.;rtc ol yot111g li/;il.ds colnp;~l.etl with that of ;~clt~lts. ~ cssc~~ti;~llythe s;lnlc ;IS thr g1.owtI1 I.;IIC of ;III ~~~il)~.okc~it;til. HOWCVCI., W~~CII the I)as:tl gl.owth pll~stllc l.cgener;rti\,e gl-owth is c.oi~si(le~.etl,the r:tte ol' tail XI-owtliis ~norc1-;11)itl than is the rate in li~;trtlswit11 11rlb1-okci1titils. Thcre- l'orc, the v;~lucof ~.cgener:rtiori lies not only ill the ~.el,l:tc.ernent ol the tail 1,111 ~.cl,l;~cc~nent;it ;I r;~tcf;tsier tli;111 wt~~l~lI)e possil~le witllol~t tlie regen- er;tlivc process. RI,:(;KNII~AIION01; I%UOI li/;l~-tls(al~turetl, fol- ex;~ml)le,at 27 111111, IVCI-c1101 ~-ct;~l)t~~reclr~~ltil they were 40 mm. Others were not reC;rl)t~~~.etl11nti1 they hat1 re;~chedmi~limutn size at maturity in wllicli case they co~rltlno longer be co~lsitlerctljuveniles. 3. Too long ;I periotl elapsed bctwccn I-ccal~tui-es.If :I li~;irtlwhose tail was broken in Octol~erwere not recal)tr~re(lu~ltil I;el)r~~i~ry, ;rt which time rcgctic~-;itioll1v;rs complete, the time i-ec1r~il.etlfor I-egencration, :untl I~cnce tl~c1.;1tc, co111d ~iotbe deterniinetl. 1. Most t;rils were broken between captures. In these c;ises tlie tl;ite of the break was ~iot~I~~MJII, SO the (1;rt:r on this ;~~lim:rlwere ~iithoutvalue. 5. Fin;llly, I~cc.al~seol' error, tl~cinvestig;~tor sometimes Iailetl to rne;isr~rethe tail base ;rntl I-egcncl-atetl 1);w~. \lrheli ;ill of the tlat;r at-e cr~lletlSol- tllr ;ll)o~.ere;rsolls, little is left, ill sonie c;~scstoo little to ;tcc.o~ill)lishtlie srirtetl ~III-11oscs.Ncvc~.theless, the (I;II;I a-e strong lot- c.ertain si/es ant1 se;rsons ant1 the tl-cntls are gene)-;illy evitlcnt ('1';tble 17). l'l~ct;rl)r~l;rr tl;~t;~ intlic;~te the follo~iing: 1. 1i;lres of ~.ege~~c~-;rtio~t;11.cgc.~~cr;~lly l';~ste~. in nl;~lcstl~i~n in l'c~n;tles. 2. liatcs of ~.cgct~c~.;~tion;II.~;11ioot tllc s;mlc' ill sl)~-itlg;III ~IEASRATES OF RE,GESERATIOSA~D OF GROWTH OF T-~ILB%SE (in millimeters per da!) FOR LIZ.ARDSOF DIFFERE~TS~zts AT DIFFERESTSE.%SO\S Only data \ I1 June-Aug. .29 133) .I5 .49 ( 2) .51 - - .23 (25) .36 .29 ( 1) ,613 -- Sept .-NO~. .18 1 3) .31 .08 ( 1) .I+ .OO ( 1) .36 .li ( I) .I1 .I5 ( 3) .19 -- Juvetliles Atlultc Juvenile? Adults .18 (30) .ij 0 ( 1) .23 .13 (35) .36 .02 (10) .39 - Rollran 1111111ct.alsreCer to bve;~k~msitio~i, ~vhethcr in lirst tllirtl, etc. All limt-tls ;\re jc~venilcs Sl~o~~l-vc~lt hl;~les I;em;~les ------. - -- - - Irl~gtll,Inm T 11 111 1 I I 111 - ~ - . ~~- 2 I 3 2 2 1 $1 :i 5 "7 12 22 3.3 2" I I 37 28 I2 23 37 25 13 5 9 30 1.1 24 3 7 25 13 '1 2 31 1(i 25 40 26 1 :I 4 I 3ii 14 2(i 42 29 I5 <5{ -.1) 55 5 7 1 11 54 45 21 .I:<" 5(i 34 19 ti l ,IS 2 1 3.4 (i0 4 I 2 1 65 52 2ii 55 (il 4 2 2 I 67 52 26 :I (i ii.1 4 2 2 1 (is) 53 26 '0 *,- 37 Gfi 43 2 1 I .. .IJ 2ii 3 X (ii -15 2 I ,-<>I- 5 (i "(i :$!I (is 4 G 21 7 4 57 20 4 0 (i9 47 23 7(i 55 2ii .I I ii1I ,I7 23 76 55 2ii 11 2 (;!I 4 7 23 4 :I 7 5 49 23 4.1 7 l 50 25 4 5 75 50 25 -- - ~p~ I atcs betweell intlivi~lu~~lli/;trtl\ ;tnd betweell seasolis make it tlifhct~l~to use tlie t;~l)leSol. intlivit1u;tl ;tni~n;tls.It is nevertlleless useful lor predicting the Inc;tn 1)miotl rccluil-ed lor rcgrowt11 of a b~.okent;~il in ;I series of 1iz;lrds of ;I given six. Unfo~tun;ttcly,time since the break was illcun.ed cannot be ~)retlic.tctlbecause of elongation of the tail base. Some good information on 1;1il regc~ler;~tionis ;tv;til:tble ill the ~):~pc~,sol Ul;tir, ll)(iO: Fitc.11, 1954; Bar- wick, 1!)59; ;tnd (:;tglc, I!)/llilr. All ;tl~thorsagree t11;tt regcner:ttio~l is faster in tails that ;\re broken 111-osinlally (he ~n;~jorily,ilrc.itlentally) atltl the rate ol b;ts;tl g~.o~~tliis I';tstel. in t;tils 111.okc11(listally. Maximum rates of more than 1 mm ~-cgenct.ation1x1 tl;ty Iiave been reportecl by sevcral ;~utliors (Blair, 1960; Breckcnridge, 19.13; Fitch, 1958; Uarwick, 1959). 11 rate of 0.5 niln per day is about the average reported in the literature. Breaks tl~ror~glltile regenerated part of a tail have been reported by Blair (1960) :uitl Fitch (1940), but 1 have not observed this in utas. However, one of my stutlcnts (Cllarlcs ILIcKinney) has intetltionxlly rnatle such breaks in tlie 1abor;ttol.y ant1 obt;~inetlnormal regeneration. FI~KQIIICNCYOF TAII. BREAKS.-I have selected those individuals marked as hittchli~lgsthat s11rvivec1 to tn;~t~lrityto discover the frequency of tail breaks during the lifetime of ;in inclivitlual. A~nollgthis group I have selectecl only those individuals recal,tured ;I suficicnt nu~nberof times to be certai~~of tlie ~lrln~l>e~-of breaks incwl.ecl (Table 20). FKI.QIIFN(:Y01: BKL.\I NI~I~II~C~ hli~lcs Felnales ------1%1enks :\rc,aI Aleall 'l.o1:11 .41.ca I reI I Total -- .. - - -.- 0 ?(i 27 0 3 I) 4 1 0 1 'I? 37 79 5 3 67 120 ...> 20 If 72 3; 17 Mi On ;I~.c;II tllcre was 1.00 111.c;tk 1)cl- intlivitlual, on the average, among 91 ~rl;tles; on ill-c;~11, 1.03 breaks ;trrlong 8(i. There was an average of 1.02 breaks per int1ivitlr1;tl among 122 le~naleson area 1, ,811 among 127 females fro111 areit 11. 111 a11 12(i int1ivitlu;tls there were 405 breaks or bout .95 per intlivitlual. The I'1.equcncy ;ttnolig rii;tles was only slightly higher than that of l'e~n;tles. Al~outone-tl~ird ol' the 1iy;lrtls rc~rcllctlm;~tl~l-ity witliot~t sustaining a tail bre;tk, ;111cl ~.;rrelyw;ts the tail I)~.okcnmore tll:tn t~vic.c.However, regen- et.;~lio~~lrxi been observed after four successive breaks, ;untl tliere seems little tloul~tt11;tt tlie process coultl l~eintlefinitely relx:~tedwere it not for tlie fact th;~tthe tail I,;tse ill ;rtlults does not inc~.easein length after ;I break. In juveniles tlie tail 1);rse 11i;ty elongate IIlitliy ~nillinletersafter :I break so that ;I scc.ontl break ni;ty be, relatively speaki~lg,in the same position as the first. '1-lle 1'1.eq~1cnc.yof breaks rcportetl here is probably not characteristic of the ~u~tlisturbedpopulation. The frequency of breaks observecl in the study ;tI-e;ls is itl~olrttlou1)lc th;rt oljservetl in large samples lroin outside the areas. 'lhe dat;r ;we inclr~tledto demonstr;~tethat multiple tail fractures are possible ;~ncl,;issuming cqui11 pressures by tlle investigators on e:rch sex, they arc ;~bou~21s c.ommon among females as males. This finding may seem surl)rising, br~tw;rs not ~~nexpcctctlin view of the higllly aggressive nature of tile females. 13l;lir (IWiO) repol.tctl th;~ttail bl.eaks occ~~rreclin 15 per cent of l-year- old fenl;~les,2.1 pel. cent of n~;rles;in 22 per cent oT 2-year-oltl females, 35 per cent of ni;rlcs; ;lntl in 35 pel- cent ant1 50 per cent of 3-year-old females and m;rlcs, rcsl~cctively,of S(,rloporrrs oliutrccrrs. In this species, ;~ggressive encounters ;lrc evitle~ltlyrestrictetl to the males. Cagle (19/l(ib) st:rtetl that ;~l)or~t30 per cent of tllc gccko Nonitltrc~ty1~r.sgertroti hat1 regenerated tails 21s ;\dults, about three times the proportion observecl in young. Ap1j;lrently little is known about the lrequency of multiple breaks in the same indivitlual, but even so, the high proportion of breaks reported in the litcrat~rreamong atlrrlts coml)zrrctl with juveniles attests to the impor- tance of the breakage ;u~tlregenel,;rtion mechanism. It has solneti~rlesbeen ;rss~~medthat the l'l.ecluency of breaks is directly proportional to predator pressure on ;I pol~~llation.This IlliiY be true, but breaks also occur during :~ggressivcencounters, l);u-ticl~larlyIxtween males. I3~1st;1rd;rntl Hughes (l!)(i(i) hz~ve,rather curiously, atteml>tecl to derive ;tver;lgc ;~gcsfor liz;rrtls in ;I natural pop~11;rtionfrom tail-loss data. How- ever, the tail-loss data, beca~~scthey m~~stbe obtained from recapture of marked anirrl;~ls,become supel-fluous ant1 even poorer than the original ~-ec;~l~tui'ed;~t;r. This is bec;inse estirn;rtcs from the tail-loss data restrict consitlcr;~tio~rto those ;~ni~n;~lsamong those 111;1rketlthat sustainetl a bl-oken tail. Ut;rs sl)encl rc1;rtively littlc time for:~ging Sor food. Our consistent im~xessioti,g;iinetl horn watching individu;~ls lor many liours, has been tI1;1t tllcse li/:~~.dsare oppo~-t~~riisticfectle1-s, i.c., they will reatlily cat allnost any inscct oc suit;rble size that passes near thein when they are basking or moving :rl)or~tin tlleir lionle ranges. Llt;rs leetl tllro~rgllo~ttlrc year when tcmljel.atures are cond~~civeto ;tctivity. 1 have t111g trtas with 1~111stom;~c.hs from winter retreats, intlicating that tlicy 11x1 Cerl rccerltly. I 1i;rve also found that food is abundant in winter, when the ston~;~c.hsof ut;~sus~r:rlly cont;tin I;r~.v;reof moths ant1 beetles that occiu. in ab~rnt1;rirce ljencatll surl';rcc c.o\'e~-:u~d in tllc loose santl arou~lcl l>ackt.;~t~lcsts. Uotl~ of these sites arc Ireqllentetl by t~tastl~u-i11g the winter. l'ermitcs ;we also obtainable ill the wiilter ant1 211-e lotlntl fi-ecl~~entlyin tllc scom~~c~hs01' ttcas. 011 Febl.u;~ry 18, lS(i3, six 01' 11 utas th;lt were I'o~~tltI frozen lollowit~g;I sc\/erc c.oltl spell 1l;ltl 1'1111 sto~rl;~clls;t11(1 a11 contiti~led some loocl. In l;tljot-;~toryexl)el.ii~leilts 11t;ls on long (lays consislcntly gained Illore wcigllt ~ll:to tilose on shor~ci-ones. This is consistent with the cxperinlent;~l 1.cs~1lts01' Fox ;III(I 1)essaucl. (1957) on tl~es;~lt~t;u.y elfect of long clay le~lgtlis on tlie ;~l)l>etitcsof li/;~l.tls(/l~roli.c). 1ll;ls ill the I;lbor;~tory will feet1 on ;thnost ~llovitlgii~se(.ts; 111e i~ltel.cstoE tlie li/;u.tl seellls tlirec.tly p~.ol)o~.- tio11a1lo tl~e;tc.tivity of the prey 'l'ile only stl~alll'ootl itclns tll;~tttt;~s usually :~\rc)i(l:IIY reel ;IIIIS,:~ltl~o~~gll ;III occ~~siot~:~l li/;11.(1 ufill eat tIle111 ;IIIC~all of t1le111eat ~IIIII~~)~I.SoC s111;11l l)1:1( k oi~cs. 111 loiig pel.iotls of fieltl obse~.vatio~lwe 1l;tve :1ct11;11lyobsc~.vetl LI~;IS e;tti~~gtltc I'ollowit~g111,ey: l)l;t( k :111ts,1.et1 ~III~S(r;t~.ely), le;~Il~o~)pe~~s, c;11.;11ji(l bee~lcs,g~.;~sslloljl)c~.s, iulcl cate~.l>ill;~i-s.In tlt1.ee inst;~nccsurc countetl the 11~111ll)eror Icecliilgs. 011 ,Jt~r~e3, 1!)(;2, ;III ;rtlult l'eni;~lcresting beside ;I col- Lmin or :111ls ate tlieill ;t rate of 25-30 1)rr 10-~uinuteobse~.v;ttion pcriotl. On Tuly 4, 1962, ;I leln;~le;IL~ (i0 tillles hctu~cctl 1530 ;111(1 2030, ant1 W;IS obsei.vet1 to e;tt I!) i~iscctsI)etwcct~ IS00 ;11it1 1900. Finally, ;ti1 ;ltlrllt lnnle ate 50 ;ti~tsl)et~~c't~ 155(i ant1 2030 on lu11c 27, l!)(i2. htIost of these i.ccortls were III:I~~~(!LII.~II~ pel-io(ls wl1r11 tile li/;~rtls wcre ~.el;~tivelyi~~;~c.ti\~c!, pel-iotlit.;tlly I):tskillg itntl fcetli~lg;~i.outltl :I ~):ti.ticul;~rp1;11lt. At such ti111es they will I'cetl if the ot)l)ortutlity is p~'(~sc~ltctl,sonletinlcs j~titil)it~gsevet.;~l i~lcllcsI'I.~III rlle gl orl~rtlto c;ltcll ;I ~viilgctlinsect tl1;11 112s 1;ultlrtl abovc tllcil- Ileati. Large s;tlnpl(:s ol' ut;ts l'1.on1 ti lost inontlls of the yeill- wel-e collectctl early ill this stutly. Tllesc were n~;ttlc;~vail;~l)lc to b\Tilli:t~~i\!\I. bli1stc;td of llre IJlliversity of R1isso11i.i ;tt 1<:1ns;1s(lily for ~iscin his stutlics 01' c.oml,ar;l- rive! l'ootl Ii;~l)itsof li/;~rcls.1h.. R~1ilste;rtlh;ls gct~erotlslyl)ro\~itletl llis res~~lls to II~C1'01. in(.l~~sio~~ lxcre. 'I'i~es[o111;1(l1 cor~tet~ts ol' s;trnj~lcs oC li/;~rtlsselec.tetl by Milste;~tl to covel. rllost of tl~c;lcli\~ity pel.iotl ol tl~c11t;ls were :un:~ly/etlvol~~~neti-ic;~ll~ to tletei.mine the proporlion of e;~c,hfoot1 iteni in tltc total s;~~nl)le.Tlte sainplcs usctl ~1rc.1-ec.ollec~tetl ill 1!)5!) ant1 I!)(iO, IIIIL l'1.om sliglltly tlifrere~lt ti~lle 1)el'iotls ill the two years, 1\11 s;unll)les c>ullc f1.oln the vic.inity of tll? st~~tly :1re:1s. Air ;tnnlysis oC the sto~li;~cl~co~ltc~lts (7';11>lc 21) i~l(lic.;ttestll;tt 11t;ls will l'ectl 111m11 ;illy insect o~ ;~~.;tc.h~liclof stlit:tblc si/c. I'his reirlfo~.ceslrly i~ril,rcs- sions that they ;II-~oljl)o~.ctulistic in their l'ootl c.11oic.e. No coilc.lusio~lscon- 1cm>c*z q? 0 o -m o-r CO ,O 01 OCI C? rrw- q n c ni oi oi I. + i- - -t. M cerlling l'ootl l,rel'e~-el~c.c~;III be ~n;ttlcI)cc.;~l~sc I I1;rve no (I;II;I on tlie ~-cl;itive al)utltl;~tlc.eof tlle prey items irl nature. I I~.eq~rcl~tlyobsel.vetl ut;ls feeding ulm11 ants ant1 srn;ill I~eetlesin the fieltl, ant1 these two ite~nsmade 111~over 50 per cult 01' tl~el'ootl (.ontents in the s:unl,les ol both yea1.s. Irl ;~clditio~~, tlicsc items gellel.;~llyoc.c.u~.retl ill ;I Iligh ~)~'ol)(x'tionof the ston~;icl~sol' li/;il.tls ill ;111 of tl~es;~~r~l,les. 'l'l~et~tas cvitlently l'ectl III)~IItllosc items th;it are most ;II)IIII(I;II~~.Prey slxcics th;~~,ill 111ost s;~lnl)les,1n;lkc III) ;I sm;ill l,o~.tionof the tliet oc.ci~siol~;~lly 111;tke "1) ;I vuy 1;11'gcI,el.c.c11t;lgc. I;or cs;ill~l)le,;i~.;~clinitls ill the May 28, 1!)5<),s;~ll~l>lc ;III(I I~cir~il)te~.;illsill the I;cl)rt~;~ry25 :~ntlM;l~.ell 15 s;unl)lcs ol' the salnc ye;rl-. Nole ;11so th;tt ot-thol~(et.;~~is1vel.c 1lnc.olrllllon it1 tllc diet ill l!)5!), I)[IL rel;~tivelyl'rcqt~c~~t it1 I<)(iO. 011~s;IIII~)~~, tI1;it 01' Iuly 5, l!)(iO, was coml)osctl e11tii.ely of jllven:~l li~a~xls;111tl t11;it 01' f\tlgust IS was 1;11.gclyol' yot~lig.111 both, ants c.o~np~.isctl ovcl. 50 I)et. c'ent of tl~ccliet. This obsel.v;~tio~~is c.cl.t;ri~~ly cor~sistent tvitl~ i111lx.essionsg;~illctl l'ronr w;~tc.lringyo~111g ;111in1;ils while tllcty l'ctl. (:onsistel~t sc;1so11;11cll;uiges ill diet ;il.c 1101 c.le:~~-lyp~.csent. This is ~~)ssil)lythe l.esult ol' collec.ting irrdi~it111;ils1'1-on1 tlillerellt tnic.~.oh,'I l11 ' t;its tlu~.illgtlifferent s;~lrll)ling~)e~.iods. ];or ex;tl~rple,on c.oltl, c.lolttly tl;~ys tlie li/;~~.tlscvo[tltl I~avcI)een c.ollec.tctl I~ene;~thsurfac.c tlc1~t.i~;o11 c.oltl, c.le;~t. tl;~ysthey likely were c.ollec.tec1 ;1ro~111cll)ackr;~t nests. 1 wol~ltllike to go somew11;rt I~eyontlthe cI;tt;l in c.onsitlel.ing tl~evolulne of foot1 catell. 'I'l~eweigl~t of the foot1 ~.emovetlby hlilste:~tl l'ron~the ston~;rc.l~sol' :idults W;IS (.o~~sistel~tlynro1111~1 0.1 gin e;~c.h.I~l;isln~~c.ll as :I l)ei'iotl ol' 2-3 hours sorrletilrles e1al)setl between c;iI)ture of tl~c;~l~iln;~l ant1 its l)t'escrv;~tion,sonic tligestion may 11;1ve taken 1)lac.e. If' a li~al-tlwet-c e;~ting;~l)o~rt 0.1 gl.:un of foot1 IKI- (lily, the11 ;in ;rvcl.;lge resiclel~tatlttlt I~~III- littion of :1bo11t l(i li/;trcls ])el' iic1.e wot~ltl1.eclui1.e or~ly bout 1.5 gr;~lnsof insects 1)cr tl;ry. Igrloring tl~eJitver~iles, it seems likely tll;ct the rtt;ls c.;crlllot bc col~sitlcl.ctla 111;ljc)r link ill tlre energy Ilow ill their ecosystem. 1);lta on tliis l,oitrt ;II-C nec(letl. I). I<. Jolinson (1Wi1i) estim;itctl ;In energy ;issimilatiol~ by two slxcies of igu;initl li/;u-cis of 50-75 c.;llo~.icspel- gram ],el- clay. 'I'hese 1igt11.e~;tgr.ee well with IKI~c.ontcr~tiol~ c.o~lc.criling energy How ;is nrell ;IS with c ;il(.~~l;ttetlellei.gy exl)cl~tlit~~rctl;~t;~ (59 c.;rl. pel- ~I,:IIII pel' (lay) for the lir;il.tl Scrloporlrs oc.cirlc,lf(ilis(hlc.iV;ib, 1963). l-I;ll.~.is(1964) ill ;I sttitly of Ag(rttrti cigcittitr in :\I'I-ic;~ rcl)o~-tctl;I [oo(l i11t;lkc of about ,015 grn I)el' gram of I)otly aveigllt per tl;~y.'I'l~e ;~tlult 111;llc Il,q~tti~i;IV~I.;I~CS ;tbottt 80 ~~;IIIIS,the l'emalc 30, so tile estilil;~tctl inlirkc of this large s1)ccies is not g~.ei~rlytlilI'el.ent per gri11n fl.onl that for litrl. 'I'l~;~nks1;irgely to the cll'oi-ts of I Wlortality is tlillicult to rne;~sl~rein natul-a1 populations. 111 t1lous:tntls ol' liol~l-sof obser\~;rtio~iof ut:~svery few instances ol pretl;~tion01- tleatli were ol,set.\lctl; yet tlie rapitl tlisappearance of young lim~.clsI'roiii tlic ~)ol)ul;~tioil was ol)vior~sfro111 otrr field tl;~ta.Even when pret1;ltion c;ui he observetl or tliscovcl.et1 rllrotrgll exaniination of the ston1;rchs of l~red;~torsthere is still no w;~yof tlcterlnitiing from such tl:lta the inll~cenceof 111 cdation or1 ille pol~tll;rtionTherefore, I will limit this tliscussion to a consiilcr;~tionof the know11 c;rlrses of intli\,itlr~almortality and, in ;I later section, will t1isc.t~~~ ~rio~~t;rlity1.atcs oS llle ],olxilation. Sunkcs ;tnd l)rctl;\ccolrs lizards were cauglit ~rheneverthey were seen in tile sttltly ;Ireas and the stoinacl~contents 1-elnovet1 by p;~lpation.In this w;ly I 11;rve c.ollcc-tctl itlost of the ~~rctlirlionrec:ortls below: ,Jrlrie 3, 1963, fl..,lgnlcnts of I/((/ fount1 in pellets of burl-owing owl; ,ltlly 12, IO(i3, Cirrttii- (10;13/10.1.1rstigris shot on this (late had a llatchling Utct ill its mouth; July 1, I!)(i4, ;1tlr11t I'elu;~lcUt(r containecl hatchling in stomach; Sel~teinhel-1.1, I!)G/l, ;I ~ri;~l.ketlIJltr was r-e~liovctlfrolri the stomach of a iliglit snake (Ny;b.rigle~~cr /ortlr~(r/cr);iLl;rrcli 1.1, l!)(i5, ;k m;u-kctl m:tlc Utcr reinovetl from tile ston~ach of a lxliric rattlesnake (Ct-oi(lll~sni~itlis); Septerriber 5, 1963, m;u-ketl m;rle [I((/ ~.eliiovctlf~.oin sto1n;lc.h of an ;~(lultleol~artl lizartl (C~.otnplrytrts-cui.rli- zorri); /\rlgrlst 20, 1'3(iil, markctl fcm;lle Ula renlovetl from the stomach ol ;t ,j~rvcn:~l1eol);u-cl 1ir;n-tl. l'liese 7 I-ecortls, 4 of wllic.11 involvetl lnarkecl utas, are a11 th;rt we Il;r\,e ;r\~;ril;tl)lcI'r.oul the study areas or- theii- irn~nediatest11.1-ouritlings. Ilowe\,el-, c1~11-ingthe c;irly phases ol this study, :i large ntin~be~.of nocturnally acti1.e snakes were collectetl by driving roads in the area at night. Two of my st~itlents(blcl So. ol i~rstal~ccs No. of snahcs of prul;~[ionolt I'ta c~~tttti~~c~l C)tlicr ~)otu~ti;il~,retl;~tol.s of utas sucll ;IS I.c~tt~propelri.sgcrlllris, Pitrio- phis ctrt(,trifcr, ;ultl (:rottilu.s 7)i~idisdid not (.o~lt;~itlremains ol' ut;~s.A11 of these sl,ec.ics with tlie exc.eption of .Si.strrirlis have been recortled ill tllc study :~rc:is;rntl, tlcspitc the a11senc.c of cleiu. ~)rool,~~~ldoubtetlly take ;L hc;~vytoll ol' li/i~~.(ls.'l'he d;it;t ;rl)o~zcgive ;I so~newhatfalse picture ol' the toll bec;tuse most sto111ac.h~ol' tllc snakes were crnljty. Of the 152 w;ikes al)ove, 35 cotl- taillet1 p~.ey,so I"';ISW~IT present in abottt 55 per cent ol' the 1'1111 stotnaclis. M/INTII FKk~[ilhh(:>01, 1~1~,,\11~~kIOh(, LA~,\KI)\ (;OI,I.E(:II 11 ~110~1L,.\II. FILL, 10 1'..4Kl.> sl~Kl>(; FOR Ill1 I'IJKIY)~~OP 01, lP! ~ - - -. ppp - 1)at.c No. Loulrtl No. tlcatl I'cr cent cle;~tl Situation -~ - - .- .. - L", Oct. 57 17 2 12 Sur1;lc.e litter 1.3 ]el). 5!l 10 0 - Susl'ace litlrr 22 1)cr. til 25 0 - U~~riedirr sand 13 ,j;111. 62 5 l 11 28 llr~licdin sat~tl 27 ~:III.62 52 X 15 Iluried ill santl 3 ~I~II-.(72 1 3 0 I~III-ictlill sirl~d 3 ,J:III. (;3 20 0 - I 3, l!)(i2, we Coulltl no cleat1 liz;~rtlstlesl~itc low te~nl)er;rtr~res.Sl~ow Sell again prior to ot~rnext ;rtlernpt lo fintl bl~rietllizartls on I;el)ru;~i-y17, at m'llicll time allnost onc-lourth ol those t'ountl wcre tle;~tl. Tlicsc tleatl were all bclic;~th~III-face cover; 2 of 15 (lug f~.onithe s;lncl were tlc;ctl. Tllc air tem- pcr;~turesfollowing the Febr~~;~rysnow wcre consitle~.:~blyhigher than those that prev;~ilctl in la~ru;~ry,intlicating that the snow cover I-ather than low te~~i~~ratu~.cs~liiglltbc lrioi-e inl~~ortantill the ~no~-t;~lityof the li~ards. 7'11~~noisturc Sro~lr tllc ~nclti~lgsilow 1,ercolates thi.ougli the soil, tlisl~laccs air t~.:~pl)etlin tlre s:~~itl,anti ;~llowssubsul-1';tc.c teiril)e~-;~t~~rcsto fall. In colit~-;~stto tlic obsel-vations ;~l~oveare those of 1)ecember 10, 19(iS, wllc~~,following stlow ;111tl st~l)fl-cc/iligwe;~thei-, 11o1le 01' 50 11t;ls I'oulltl TV;IS tleatl. Sul)ll.ce~ingtenil~ei.;~ttlres 211 nigh1 are cllar:~c-teristic 01 the winlel-s in ~~ol.thweste~.riTexas. T11e1-e is 110 intlicatio~ltli;~t these normal periotls of c.oltl we;~tliel-;Il.e clet~.i~r~cntalto the 1i~;ir.d~.Periotls when the tclnperatures tlrlri~lgthe cl;ry (lo liot rise above Ireeling arc uncommon, hut tlo occur every winter. These, loo, ~~l.ob;tblyhave liltlc cllect. It is the occ;~sion;~loccllrrenc.es 01' l~.olongetl~)criotls ol very low te~nl,el.atu~-esnear or below ~erowill1 some s11ow COVCI. t11;1t ;ire resl)onsible, at least i~~tli~~cctly,for the winte~.kill. /\ss~~~rii~lgt11;tt li~;~~-tls that wc have dug from the sand or rcco\,el.etl belleat11 sr11.1';rcetlt:l~ris rel)reselrt the populii~ion ;IS ;I whole, it is ;~l)l);lrentth;~t 11nrls11:11~)cl.iotix of' severc ~leatllcrmiry kill 25 per ccllt ol the ~.csitlent li/artls. /ill 10 observatiolls in Table 22 intlicate a rnoi-tality ol about 14 per cent ever1 il observations are inclrltletl in which no tle:~tl lizal-tls were lo~~ncl.I1 tllese are exclr~tled,;r ~iiorlalityin excess of 20 per cent is i~lclicatetl. i\tltlition;rl tl;rt;r :rv;ril;rblc on sutll 1';1ttol.s as clcptll of I)u~.ial,sex, ;111(l 01' tlie li/a1-(1s ill reli~tionto total mort;~lity.At a tlcl~tliof 1-3 incllcs ill the s;~ntl,only 17 per cent of the utas were tle;rtl; ;it 4-6 inches, 12 ])el. (.(lit; :I( 7-!) i~lc.lies,7 per cent; at 10-12 inclles, 15 pel- cent. I\/lo~-talityis Iiiglicst ;I[ tliat tlel)tll a1 which soil te~llpei-attu-eis lowest (luring tllc (lay. The clat;~oS Febi-t~ai-y17 ;rntl 19, l9(i3, from lizards ~.ernovetl J'I-OI~ str~-f;rce tlel~risintlic;rtetl th;lt mo~-t;rlityin suc.11 exy>osetl sittl;rtio~lsw;rs tlolrble th;~t ol)sc~.\~etlamong li/a~.tlsbr11.ietl in s;r~ltl. Rlrillcs ;IIT n1ol.c susccptil)le th;rn len1;rles to wintel- kill. Of SO!) live ;rni~il;rlsin wliicli sex was tlete~.n~inetltltrl-ing ot~rohsel-vations on urintcr kill, I(i9 (55 per c'cnt) were I'elnales ant1 45 per cent were nlalcs. Tliis is ;11)l)1'oxirll;rtclytllc sex ratio in 1;rrge s;r~n~~lesof atlt~lts 1'1-om LIIC l)ol)t~l;rtio~i ;rt Inost seasons of tlic yca~..tlowevc~., ;lmong the tleatl liz;~l.tls,tlie sex 1.;1t io w;rs I)I:/i!) in I';~vor01' the ITI;IICS.Nilictcerl 11~1- cent of tlcatl li/;u-(Is l'otrlrtl wc~.c~n;rlcs ;rntl 15 1)el- (,elit fcm;rles. This higllei- mortality of ni;rlcs is one of the 1'ac.tol.s ~)rotlut.illgthe 11i;rsctl scx l-irtio ill the l)ol)t~l;rtionth;~t is tlis- c.ussetl in ;I 1;rtel. section. 0;rt;r 011 ~llo~-t;~licy;rn1ong 1i~;rrcls01' tlillere~ltsizes (IIII-~I~~111r wi11te1. are 111(';1xc1. I~CC;I~ISC~ne;rstr~-e~rlr~lts we1.c t;tken 01' e;tc-11 lizal-tl only tlt~~.irigtllc oI)sc~.v;rtio~~s01' J;II~~I;II.~ 13 ant1 J:III~I;II.~25, l!)(i2. rI.lic l)c~-(-en~;~ges01' (le;~tl ;Ilriong thc 3 ~-.?~-I~III,3(i- lO-~nm, l-/l5-n111i, 4(i-50-111111, :11i(1 5 1-5.1-111111si/e gror~pswcrc 18, 31, I!), 15, :rntl 3.1, I-esl>ecti\,ely. 011ei.e;rson Sol- the lliglier mortality ill the 1;rl-gest six g~.oul)is tll;rt a11 of the ;rni~n;rlsill the group were ~rlales.I tlo not know the 1-e;1so11lor tlie liigli mortality a11io11g~II? S~i-4O-n1n1;r~limals, bur uroultl 1"-cfcr to ;~ttl-ibt~tcthis IO s;r~iipli~i~l)i;15. ~\IOR.~~\I,I.I.Y( ;AIISI.:I) I~Y H~~~~~.~i\l(;.--IJ~ifo~.ttr~l;r~ely, 111c i~i\~estig;~tor~ the~ilsclvcswere ~.esl,ollsible lor some tleaths. Young 11i;rs are c1uitc small ;~ntlclclic.;ttc. ;r~i(llnl~st 1)c cal~tu~.?tlwith very grwt cal-e to ;~voitlin.1~11-y. 7'11c h;rtc.hlings we1.c h;rntllctl ill 1;u.ge numbel-s beginning in I!)(il ~vlicnwe in;ltl- \,c~.cel~tlykilletl abolrt 5 pel- cent of tlieni. I;orttrn;ttely, o111-~-cc.o~-tl in~l~ro\,ctl ill srrcc.ectli~rgyea1.s ;IS tlie tlac;~below intlic.;rte: We killetl 105 ol 3402 li/,rltls I~;intlletl, ,t to~lt~il)t~~ionol ;rl)orlt 3 1)c1 T~I-ATIIS I;KOM ~JNICNOWN (;i\r~s~:s.-EightI-~COI-~S 01' t1e;ith among utas on the sttrtly ;rrc;ts wcl-e lronl rtnknown calises. Seven ol tliese were atlults, ol wllieI1 5 we1.e si~nplylountl tle;itl; one had been cal,tu~.ctl ant1 released in gootl c.ontlit ior~the clay bcf'ore its tleatll. 7'he ochei- two aclults were s~rsljected vic.tin~sol l'~.cc/ing.'l'he single juve~~iilli~artl w;rs forrntl tlc;~tlwith no evi- tlcnc:e ol ~>rctl:rtio~lor l'rce~ing. (;;rn t hcsc clc;~tlns be rrsecl ;IS e\#itlent c thirt tllc annu;il tit~-ilo\/crin thc lx)l~~li~tio~lsis :un intlic 21tion ol ;I sl~ortphysiologic;~l lil'e cxl~cctancy?Pcrlial,s not, 1)itt the I';rct th;rt ;111 I~utone wel-c irtlults iincl th;rt these lizal-tls h;ive 1)1'o\lc11(liflicul~ to nlaint;rin lor long 1x1-iotls in the laljoriitory lend cl-etlence 10 111~itl~i~. 71'l~ct-irriscs of ~no~.t;rlityof intli\,itlu;~lli~;~~.tls are ~)oo~.ly known. Many stlttlics list ~~ote~~ti;~l])~.etl;ito~.s, Ijnt it is I-al-e(see H;r~-~.is,I!)(i~l) that p~-ediition is ;~c-trlallyobscl.vetl, ant1 never has its in~port;~lrcein contl-olling ~~ol)irlations of li/;i~.tlsbec11 ;rsce~.t;rinetl.1 think this will be true until fieltl expel-iments rn;~nil~~l;rting~x.etl;rtion ~~~SSIII'C ;we ])el-Sol-metl. 'l'his type of experiment is j);r~.~ic.irl:t~.lyfe;rsible now with t~tirsbeca~rsc we arc ;rw;u-e of their ;rctrr;il tlensity ;~nclof [lie 1.e1:itivc clcnsitics of ~j~-etl;rto~.s.It ulo~~ltl Ije ;I sirnple Iri;rttcl. Lo ~l~;rilil~rtl;rl~either in enc-losctl areas. 1ll;ril. (I!)(iO) ~-el)o~.tetlLII;IL tile inajorily of nests (75-78 pc~.eelit 01' the clr~tcl~cs)of' S(~c1oporrtso1ivcrc.cr1.s wet-c lost to ~~rccli~to~.~,clesic.e;rtion, or some other Sac-tor. A si~nilarobscl-v;rtio~i was ~n;itleI)y Filch (1!)5(ib) on (:rotcrplry- 1r1.r r.olltrris, in which the numbel- of young Ilitcc.hing Srom riests was about o~le-h;rll'the nunlbc~.of' eggs laitl. I\ \,;~riclyof i~ljurieh:rvc been itnflic~ctlotl li/;r~.tlsdrrl.it~g tlleil. ( ;I~ILIII.C, I~rtl111;rny II;IL~II.;I~injr~rics ;11ao oc.c~~r,:IS (lo a fctv ahnol-ni;rlitirs. 1;or the sake ol colnj)lctcl~css,this inI'orm;ition is incl~~tletlbelow. rI'o~:Loss~:s.-I,oss of one or mo~-ctoes is :I colnnnoll n;itu~.;rli11j111.y in ittits. So111elosses 11n;ry 1.rst11t l'ro~x~in1111.oper toc clipping. If 21 toc is clippet1 too (lose to tl~eI);rsc, the I)lootl ant1 nerve s~rl~l)lyto an ;rtlj;icent toe m;ry be irnl);lil.ctl with suljsecl~ientloss of tll;it toc. I I~avee1imin;itctl this type of i11jui.y I'~.om~11e figul-cs on f~.eclrrcncyol toe loss sliown in Table 23. Two observ;rtions intlic.;~tcone ol the nleans by which toes iirc lost. On one occ.iision ;I j~rvcnirlilta w;is caugllt with ;I reel ant sec111.ely c1aml)etl to the Ijitsc ol toes 18 iintl I!), boll1 ol' w1lic.h were soon lost. Tn the secol~tl inslance, thc mantlibles only 01' ;I rctl ant were fountl atlachetl to the witllerctl 01' it II~;I. 'I'hcre is no tlilfeiente between juvenal male ant1 le~rliiletitas in the Irecjucncy ol toe loss, 1,111 ;~tlt~lt1ii;t1cs (o~~sistc~~tlysl~ow ;I greiltcl. frccl~iency of toe losses t11;11i (lo l'em;~les(T;~l)le 2.3). The Ireql~ency oC lost toes in ;i(1111t rn;ilcs is 5 tiines 21s high ;is in ju\,en;ll males. In Lcnialcs tl1c1.c is little tlilfe~.- ence ill the Srequency between jl~veniles;inti ;~tlt~lts. I.ossea ol toes h;ivc never been :I sei.iolrs ~)robleniin interpreting 0111- I.ec.;lpture tl;ita. Only ;ibor~t100 ol 3500 m;lrketl 1i~;lrtlslost toes. 11 s11c.11 losses occt11.1.et1bcforc we n~;irketltlic anini;ll, we sin~l~lyir~clutlctl the missing toe ;IS 1);tl.t oI that li/;ll.tl's pcl.nl;ilient r~tirnbel..IS lost ;iStei- it ~';is~n;l~-kccI the li/;lrtl's I,el.ln;inellt ntrn~bel.was ch;~ngctl;icc.o~.tlingly to ;~\.oitlconfusion in tllc I-ec.;ll,turc l.ecol.cls. l'hel-c MYIS ncrrcl. ;iny e\ritlence oS 1,arti;ll regen- el-atio~iol ;I lost toe. OTIIP:I 7 '1 ION-I I. 1-1NI 111ol.c loss oS toes or wit11 1nol.e tl;r~ll;~gcto tllcnn tl1;in ~voultlbe i11llictctl by ;111y ~n;~rki~~gcs~~cri~~ne~its. I)ISI~I.~\YI (~)IJI 1 'I'l1c:sc cnc.ot1ntel.a ~.a~.cly1-esr11t ill l.ctre;lt of tile rcsitle~lt 111;rle; alniost i~lv;~ri;~l~lyit is llie illtl.uclc1. tl~i~tflees, but so~rieli~riesonly aftel- ;I fight ill wliic.11 1)llysic;tl tl;url;~ge be inllictctl. 7'1~resitlent male, tlnl-ing such ;I [igl~c,~~s~~;tlly :111e111pts to bite tlic il~~rutleri11 the tail 01. l1:111k, 11111 I~I;I~ ;~lso1.1ls11 fol-~v;~~.tl ant1 1.;11ii the flank ol the intnlcle~with his 11e;ttl. \/\re halie ol,ser\~etl losa of tails in sut h ligl~ts;inti have seer1 tlic skin b1.okcr1 by the biting. Sc-xrs, ~)~-esu~ri;~l)lyf~.onl sl~clr enco~111tc1-s, ;ire i~-ecll~entlySountl on the 1x1~ks of ;1t111lt1n;lles. 'I'III.. I;I,:M~I.P:K~.:,\(:.~.~o~.--i~gg~.essive behavior seltloni Ii;~sbeen obser\.etl ;Ilrlong Cc~rl;rleli/;~rtls 01' any spccies. l'his is, 1 think, 11ec.:111sefemales rnove :11)o11tless th:ui 11i;rles ;~ntl;(I-e less likely to eucolunter one a~lothcr.Many 1rol11.s ol col~tinr~ol~solxel-vation II-ecluently Sail to tlisc.lose soc.i;~l in1e1.- ;rctions 1)et~veentl~cm. Howevc~., by tlie simple expetlient of int~.otlucing nori-rcsitlcnt l'c~rlalcsinto tlic \risr~;~lfield ol resitlents on my study areas, I 1i;lve been ;111le ro inc.i.e;lse the numbel- of intel-actions ol~servetl. 7'hc ~.c;~c.tion of ;I I'elnale to an in tl.l~tli~igI'em;rlc invol\,es ;In incl.e;~scill [lie bohhirig I'reqt~c~icyoC tllc resitlent antl tllcn the assnrnption ol ;1 stilf- lcggetl ;t~i(la~-c.Iie(l l)osti~re silnil;~~. to tliat 01 tl~(:;~gg~.essi~~c 1~1;11c. IVlai~~tairl- i~igsuc-11 ~~osturc,t11~ I-csitlcnt le111:1le will al~pro;~c.llthe intruding fernale with l;~tcl.;lloriclit;ltioli to Ilel. an(\ will generally ~>~~occctlinlmcdi;~tcly to the ;~tt;~c.kunless tl~c~lon-I-csitlent felii;~lc ~-etl-e;~ts. 'l'lie aggressive 1.esponsc . . ol' ;I l'cni;~lcis just ;IS \T~c~o~~s21s tllat of the male, antl she is more likely to ;~ct;~ckbefore ~)erfo~mi~lg;I long ritualistic tlisplay. Tllc 1-e;~ctionsoU :I female to a corlrting male are v;~rictl;~rrtl allrlost ;rl~v;rysi~~\,ol\sc rejec tio~~01 tlrc n~;~le.Tl~e Iiist 1-e;rc.tion to ;I 11lale is ~~sir;rlly ;I 1.ct111-nof' Ilia ;rsse~.tio~~I)ob. \\~IICIIthc ni;rlc 1)cgiils (il.(li~lg;III(~ sll~r(ltlei.- I)obl,ing, tlic Ic~ll;~lc ir~.ch;rntl givc ;III ;rggrcssi\,e tlisl)l;ry, Inay shritltler- bob, or 111;ry si~~~l~lyI.ctl.e;rt ;I shoi-t t1ist;rntc. ,\ll three nlovcmcnts ;II-cI-cjcc- tion ~~cs~)o~iscs.,\ltlro11g11 ;I i11;rIc III;I~COIII.~ ;I ~.c.j(:cti~igIcilliile sc\~c1.:11tinles bcI'o~.che is linirlly tlisc-o111-;rgctl,Iiis ;1tl\1;111tes will rievcl- clitl in col)l~l:ition 1111til tl~rf'e~~iirlc ;rcIol)ts ;I s~~l~~~iissi\~eJ)OS~III-(~.(;lirl.kc (lO(i5) ~-el)o~.~e(lt1l:rt in sc\.cr;rl sl)c(ics of' li/;~~-tls;IS long :IS tl~cSrin;rlcs co~~tiril~ctlo\ritl~~c:il eggs. ;111tl I'or sc\.c1.;11tl;rys ;rI'tc~-ovil~ositioll, they ~loulclI-eject corlrling n~;rlcs.111 tl~esc1.cjct tion c-e~-e~llo~lic.stllc I-etl ;111(1 yellow coloi- 11l;u.k~of the g~.avitl Ielri;ile MJC!I-~;~(~\~c~-tisccl to 111c 111ale ill tlic 1.cjrctio11postirrc. 'I'lrc s~~l)~~~iasi\,cbig11 of' tl~c I'c~n:rle is siml~lyOIIC of' te;~ail~gI~cr I-etrcat from tile c.oi~rtillgn~irlc ;~ntl ol lo~vc~-inghcl. I)otly ;~g;~instthc sr~l)stl-;rte. S11c.11;I i-e;lc-tion is soon I'ollowctl II~irtteml)tetl col)~rlatio~~. ~~Ol~ill.~\~l~lO~.-~~O~~1l~;ll~Ollis 11si1;111y1)1-c.(ctlc(l by tllc 1n;11e licking t11c 11;111k;III(I i11g~ri11;rI1.cgio11 01 the le~n;rlc,~)e~-Iiir~)s ;IS ;I IIIC;IIIS of 1xrciSyi11gllcr. T;ollo~'vi~~gtllis, tile 1n;rle 11au;rlly gl-;rsl)s the slioirltlcr ski11 01' the I'em;rle, I)llt hc: 111iry take Iloltl 01 tllc flank initi;rlly ;~ntll;~ter sliil't to tlir shoultlcr. 7.11~ I'em;rlc m;r), 111o\,c ~vllilc[lie 11l;rle is ;itt;~tlietl,1)trt ;~f'tei-;I fc~vsec.ontls to se\.e1.;1111li1111tes tl~e 111;ile (.III-\,CS liis l~rckst1.011g1y ill ;I Iio~-izo~~t;rlp1:11lc ;III(I ~)i~llsIlis t;~il I,crlc;rtli tllat of' tlic f'c~ll;rle.Se\,el-;il ;ltteinl)ts in;ry bc m;~tle bcf'olc the ln;rle i:, ;rl)lc to ;itt;~in ;I s;r~isf'acto~-ycol)r~l;rtory ~)ositio~i. *l'he I'c~nirle,then, I-irises lier tail, pi-csi~rn;rl)lyto S;~c.ilitalc inti-o~~lission. It is ;it tllis 1)oint ~vl1c1-ctl~c ;~l)sc~~tc of a t;ril ~nigl~tintci-lei-c: ~litllc.ol)i~l;rtiol~. If so, then ;III ir~~iln;~lwIiic.li w;rs c.;rl);~l)leof storing sl~el-niI'roln ~)l.cvio~~s ~IIS~III~II;I~~~IIS~vo~rl(lII;I\Y ;in ;r(l\~;~~lt;~ge,;IS \\~i)~~l(l ;II~irl(Ii\ri(l11;11 witli i-;rpicI 1;ril 1.cgc1lel.atio11..\cti~;rl co1)l1l;rtio11 I;IS~S 1.01. only ;I f'e~vsecontls a~itlinvol\~cs Sewel- tIl;111 ;I Ir:~lf' tlo/ell pelvic (111-lists by the m;~le;rf'tcr whicll tlle t~lo ,\c:c;~~~~aro~.-IItitsir1.e evitle~ltly aggrcssi\,e t111-ouglloirt their home 1-iinges. Tl~cy(lo 1101 1.estrict theil- tlel'ensc to ;I s~ll;rllte1.1-itol-y within thcir Iloluc I.;III~C,althoi~gli the inte~lsityof' tliei~;rgg~.cssioli 1n;ry bc gl-e:iter :11.ou1ltl sclcctctl ill-c;rs.'l'lle ;igg~.cssio~~is 1101 lilnitetl to ;I g1-011l)of tlo~ni~l:rnt;rnilnals in ;I soci;rl Iiiel-xchy ;IS la^. 21s I h;~vcobsci-1-etl. 111 tlle l;~bor;rto~.y,however, s~lc.11t1olnin;rnee hierarchies genel-ally I,ec.olne est;ll~lishctl. N u~nerollsII;~ tr~r;rl, ~rnstagetl cncoulltcl.~ TVCI-~ ol)sc~-\retl in our 11ou1-sol hcltl obse~val~or~.1 11;lvc 5electetl a few that are ~epiesentativefor clet;1iled I. 'l'he retl + ~n;rlcrctrc;itetl froni the ;i~-cl~ant1 bob (lisplay ol tl~ered neck ;rrlcl retl pltis rnale. 111 this instance the tlonlinant male was snlaller than the non-resitlent ant1 lacketl ;I coinl~letetail. 2. 1111;ltlult 1r1;rlc being pt11.siietl by a11 olxerver 1xr1rsctl in its retl-e;it when it t.;~ligI~tsight of ;illorl~c~.male in its home 1.;111gc.It im111edi;rtcly rnatle ;rgy~.essivegesrul.es row;r~.clthe intrt~tlilig~il;tlc ;r~icl drovc it away, seeln- i~iglyigno~irlg the j>rescllrc of the ol)sel-ver. 3. Tile nlost 17ic.io11sfight eve1 ol~serveclbetween in;rrkecl ~nalcutas occurretl 011 i\lx.il 19, l!)(i3. 1 I;II.I,I)Esl~t~rtrn~r~.:;u,rs ON J\(;(;I~I SOMI< (~IJ~\NT~I~I(:ATI~N01, ORSI~:KVED ~~~.~IAvIOR.-U~~~~SS (:011till~o11~ ol)scrv;ttiol~is 11i;ttlc of intlivitlu;~lli/;l~.tls, little social inter;tction will be seen in the Gcltl. I;ol- this reason, (luring some sunliners we follolretl intlivit1~1;tl 1iz;tstls ;rll tl;ry 01. lo1 ]);rt.ts or it ;~ntlreco~.tlctl a11 ol the iriter;tc.tions ant1 tl~c 1.cs111tsof them. Irl atltlitiori, one ol' lrly st~~tlents(1,o~tis Irwiri) elected to sl~endone-11:1lS ol olle sirnlmes ~rl;tkingcontin~lot~s oI~ser~;~tio~~s on a selectetl group ol sesitlcnt ~~t;ts.1;ro111 ;t11 ol' these observations, some gencr;~lstate- ments c;tn be ~natle. Sixty-nine c~o~rrtsliil~s,ol' m~lii(.li 12 I-esultetl in col)ttl:ttion, were obsel-vctl. In 57 instar~ccsllic l'c~ri:tle rejet.tetl tlic n1;tle. In only 2 of tlie 69 (lid the I)eh;tvior ol' the I'cr11;tle appc;tr to initiate the cottrtsllil~. In tl~esctwo irlst;tnc.es tlic Cem;~lc;rl~l)e;rl-etl to tliscct :~ssertiveI~olIbing towastl a nearby III;I~C.On Juric 22, l!)(i2, ;I ~n;tleco~crtetl ant1 was I-ejectctl by tlie same I'en~;tle7 ti~ricshefore losing intescst; on other occasions we have observecl ~ii;~lesth;tt lost interest alter a single rejection. In a11 instances in wlnicl~ c.ol~ttl;ttionocctt1-ret1, :tntl tlie fcmalc c.oultl be c;rtlght ant1 p;~lpatetl, she contaiuetl tlc~~clopingo\ral.iari follicles 3 mIn 01. greatel- in dia~netei-.The I'c1n;rlc ;rlw;tys rejectetl the niale \\!lien she ~J;IS c;trryit~g ol,itluc.al egxs. I:erg11sotl (I!)(i(iO) 1121s tlclllonstratctl 111;tt tlrc injectiotl 01' FSH will itlc.1-ease the 1'1-eqt~ellcyol c.ollrtsllil)s 11l;rt l.cs111t ill c.ol)ul;~tioi~11y inc.1-casing tl~e s~tl)~llissiviryol the I'em;~les. It is olnrio~~sto lne thirt lelllalc 11t;ts sllow 111ost of tlle c-llar;~c.teristics 1 h;~I ;11-c ;~ssoc.i;r t ctl wit11 the stirtc ol cstl-011s in ill;rlrnnals; it tllel-el'ore seems ~~~~;tsot~;tblcto use rllc 1~1.111CSI~OIIS 10 tlesc.ril)e their i.epl.oclt~cti\,ec.ycle. Intleetl. for sillii1;tl. I.casoils, II;tl.~-is(I!)(i,l) 11;~st~sctl the ce1111 to tlcscl.ibc t11c state oS 1~~1I.O(III( tiw I c-it(Iit1css ill li/;~~.(lsof' the gct111s/lgi1111(1. (~ol>t~I;ttio~~it1 11/11 .s. .~/i~;i!l~~q(,~i'is ;t s11o1t ;II~;I~I., 1;tstitlg 1111t ;I lew sec.ontls, ;tltllol~glr lollgc.1. 1)el.iotls Iiit\~11ce11 ol)sel,vctl. '1'11c 1)l.iel' (I~ll.i~tiotl of c.ol~ul;t~iotl;tt li1.s~let1 lne to 1)clicvc l11at tl~col)sel.\.el-s 1vci.e (list111.11i11g of lllolile sl)rlnl, II~II)l.csetlt ill 1eln;ilcs t11;rt Il;t(l 11ot 11cc11 ol)set.vctl ill c.ol)t~l;ttiol~,;~r~tl wc1.c. sclcctctl ;tt i.;rl~clolllSI.OII~ tllc ~)ol)~~l;ttiotl. 7'he 1.csr1lts ol' :tgg~.cssi\,cell( ot~~ltcl.s;tl.c SIIOTVII 1)clo~~: :\lthougl~ l'cnl;tlcs seltlo~l~nleet Ijec;rr~scol tlreil. n1ol.e lilrlitetl 11lovc- ~llcr~tsc.on~l);~l.c(l ~'tritll tlrosc ol' m;~lcs,thcy seem elZen1r1ol-e itggl.essivc. Otlc- l1i11I'ol' rllc s111;1ll~ltln~bcl. ol' I'elnirlc elrc.o~ltIcel.ser~tletl ill ;tc.t~i;rlfightillg 01- ill c~11;1sitlg;t11(1 l~i~itlgthe ~IILI~~I(!CI.by 111c i~cside~~~.I;igl~titlg ;111io1ig i11;11cs w;ts IIIII~~II.;II.~I.. 11' we tllink I>;tck to the csl~e~.illrcntsit1 the l)ells, this dilf'e1.- ctlc.c is ~.ci~tlily cx1)l;ri~l;~ljle. 111 both sexes, I-cl)c;ttetl etlcountcrs I~etweet~the sitinc li/i~~-clslr;~tl lo ;r ritt~;~li/;~tionol' tile ;tggl.essive tcl.cnlony. I[ (.ontact I)ctwect~l'c~~~;rlcs is lrss Il,cclt~entrl~itn c.ot~t;~c.l 1)clwccll 111;tles tllcrc is lcss olq)ol.t 1111iry 1'01. ~.itu;~li/;~~ion lo ~.cl,l;rc.o fighr ing ;IIII~II~felll;~lec. I)IS(:CISSION01: ( :OIII E~I::I~I:I I~I I~IIHAI~IOKIN ,1'1I1.: L,\I~oI 17~~~<~)A~LY~\(:rlvl~'~ 01: ~NI)~\~~D~J~\I.Ll~~l SOMI' COMMI.:N-~SON ~111.:LITI.:KA.~IIK~: 01..L.IZ~\KI) RII-I~\\J~oK.-~I'I~clittle ;~vail;tblc1iter;tturc on li/;trtl behavior was s~~rrlma~-i/etlrcc-ently l'l.orn i.;~thc~- tlif~crcntpoints of view by Evans (1 96 I) ant1 by Cl;ti-kc (1965). 1-el-1-itoriitlity, or at leas1 aggression, is c.liai-acteristic of most li7;1rtls stutlietl. I1 is 1101 :rlw:rys clcar th:rt the ;~ggression is tlirectctl tow;~~.tldel'ensc of ;I pai-ticlll;tr area, so it is 1)crllal)s better to speak of agg~.cssive11eli;lvior rather than territori;rlity. Tltere arc solnc spccics sxlcll as T,eiolopi.vnlci zclni/tlicn th;~t have been reported as non-:tggressivc (I3arwic.k, 1959). 'I'herc are also some in which :~ggrcssionis evidently not limitctl to e11co11ntei.s between liz;~i.tls oS thc silmc sex. l311st:trtl (1965) repol-tctl that Sc1t1;tles ol (:l~nnlclcoholi7lt:li will attack other li7i11-dsof either sex if they get too close. 1 have observctl a si1nil;tr 11ch;tvior in at leas(. one spccics ol 7Jltr in u~hic.11the female rejection response iilvolves making nlci~acii~gittlvailces itnd nil~ping;it courting males. LTntlcr natul-a1 c:ontlitions, female ;tgg~-essionh;rs 11cc.11 rel~ortedby Ev;trls (1938tr) in A~lolisstrgrc:i, by Fitcll (1!)5(iO) in Croltrphy(rrs collnris, and F1;trl.i~(19611) ill Agnnlcc ngtr?nn. 11s I I1;rve notetl Sol- II~;IS there seems to bc little 11esit;ltion on the part of ;I n~;llccor~f~.on~ctl by ;tnotlrer li~artlin exhibit- ing either aggressiol~ or co~rrlsl~il)tlel~ei~tlil~g ul)oil the sex of the otl~er. Sex I-ecognition seerns ;tln~ostiminctliatc. Noble ;rntl ISratlley (1!)33) I-el~ortetl frott~ tlicir label- tory stutlies of Anolis ccil-oli7ror.si.v that nialcs exhibitetl cor~rtsllil>1)eh:tvior towart1 other lizartls rcgartllcss oS sex, ;tntl that aggression was tlrcn elictctl by the subsequent bellavior oS tlic other li/:u-tl. Evans (I!)SXb) co~nl~iletlevitlence to intlicate tltat s~~cliMJ;IS not the case, ;rntl tll;it scx t.ec.ognilion occui.retl at :I clisl;~nce.Onc ol thc ~nitjorI-esults of aggressive I,el~;~vioris spreacling ol' the population fail-ly evci~lyir~ relation to its i.esol1rces. 1'11e fr~nc.tionmay be ;~ssoci;ttetlwith il~atingatl\r;tn(age. Howcvei-, ca~.riedto an extl-erne, ag31-ession woultl result in less efficient rttilization ol reso~rrtesin years 01- areas when the rcsourc-es wcrc u~~us~~;~lly;tljuncl;rl~t. (;otlll)ressio~i ol' tei.ritol-y six c-oultl 1-esu1t it1 :I grcatcr clctlsity ;11it1 so rnigllt the establishrr~ent of social hieritrcllies. 1x1 most studies oS lizai-tl hellavior il has been noted that some type of social Iliel-;lrcl~yis quickly cstal~lishecl1111der crowtlctl laboratory c.oi~tlitions.For example, Carpenter (I!)(iOh) ol)scrvetl tl~;rt 2 1n;rles soon I)ec;~me tlo~ni11;11itin :I gror~l~of (i cal~tivcI/rosciri~-r1.s ortrtrtris, ant1 with a little inore tinlc one of the two I)ec;~~rleclo~~iin;l~lt over the other. 14~lienthis majol- tlonlin:~ntwas removecl, the bcl~;~viorol the s~rbtlo~nin;rntanimal t 11;rngetl ;r~itl he bec;~rne the tlorninant, retaining his sociirl positiol~even after the 01-iginal tlon1in;rnt wits rctr~~.nctlto the cnc.los~rre.liemoval of botll tlomin;tnts ;rllowetl ;I tllircl lisai-tl to assume tllc clorninirnt ~~osilion.In Carpentcl-'s obser-\ration it ;~pl~earctlth;~t the tlomin;rnt lizirl-tl I)ec;rnlr tla~.ker.In ~rtas.I h;rvc o1)servetl t11;tt :I clo~ninant~n;rle ;rppears to get I~righter,~~;irtic-~rl;~rly the orange spots, (luring :cggressivc tlisl)l;rys. So~newl~atsimilar behavior of 1n;rlc li7:trtls in ;I tlomin;rnc.e syste~nwirs obscrvetl by C;arpenter (196 I) in Sccloporris ttrcrri- irltii, in whicli most ol the social intcr;lctions in ;i group ol captives l~ecitme reslricletl to two tlominants. <:l;rrkc (1965) in his ex(-ellent studies of I,ella\rior ill the 1is:rrtls kIo/- Orooltim, (~mlli.sn~irrc.s,;rntl Co$hostirrrris Fountl lormation of t1omin:rnts-sub- tloniin;~ntshierarchies in the laboratory. In his view the 1lierart.hies were 111-ol1ght;111out by the inel-c;~setlf1.eq11ency of contacts between intlivitll~als in t.onfinct1 c1rrartel.s. 111 7Jtti ~1(1rl~l)riricii1~1s11c1i I~ie~-;r~.(.llies;iIso bccolne est:rl)lisl~ctl:rntl leatl lo a retluction in strife within the entire group. 'Tllc l'reql~enc.ywith whicl1 1~icr~rrc:hiesare l'ormetl in tlic l;rbo~.:tto~.yby many sl~ccies01' li/:~rtls certainly suggests tliat, unclcl- contlitio~isof Iiigll tlcnsity, wlic~~contacts I~etwee~lintli\,itluals ;II-c incre;rsetl in the fieltl, hic~-:r~-c~I~icsnlight form in nature. Such 21 ~,lierlomenonIli~s been rcportcd by Evans (1951) in the 1;lrge igu:uiitl lisartl Cle~rostl~il.trficc.li~rtiln ant1 in the ;rgir~nitl li/:~rtl, Agcr~~rritrgc~~iti, I)y Harris (l!)(i,I), ant1 ~)erli;rl~sreac:hcs the extrcmc ill the marinc ignzrn;~ol thc Girla1j;rgos. As will bc cliscussecl l;rter, they niay also occur in some poprtl:rtions ol' utas. If hier;~~-t.hies(lo fol-1x1 in nature untler l~iglltlensitics, the inlportance ol ;rggression for controlling 1101~11:1tionsix rnigllt be qucstionetl. However, if' the breeding under a hieri~rchicalarrilngement is lirnitctl to a lew intlivid~c:~ls,popt~lation num- I~ersm;ry IIC controllecl in this wily. It renl:~ins to Ile denlonstrated, however, that sucli ;I restrictioil occ~11.sin nature. 7'11~oi~tst;~ntling work ol Harris (196'1) o~iilgcrtt~n tlcserves lurther con- sideration. Hc hi~srccortletl ;In instance or the means by wllicll territol-ial boiintl;r~.ies bcconle cst:rl)lishetl. Two males with adjoining home I-:rngcs Iougll~several times over ii l)i~tl~between their bountl;tries. Gr;rt111;111y, fighting w;ts I-educctl t111ti1the two 111:rles wot~lclbob back :rntl lo~.th;I[ one ;rnotl~c~.;~c.~.oss the ~)i~th,but woirltl sclclonl 11llysic:ally vio1:rte the bountl;rl-y. I\/lalc A wor~ltlI)e beaten when Ilc entered into 13's territory and vice versa, ~)rovitling;In excellent ex,irnple ol the psythological atlvnnt,~geenjoyed by 'I 1 esitlent li/~ri(lin 115 OTVII te1 I 1101y. H;I~I-is'work is :rlso ~tniclue1.01, its ;111;1lysisof tc1.1-itol-i;rllilnits ant1 of social Iiic~.;rrc.l~ies.1Sy ~no~irlglriotlels ol 111;llc li/;r~-tlsillto ;rri(I ;rroun(l the home range of resitlerlt lrlales Ile ~,\~;tsable to tlcfillc xvith solllc recision tllc area in ~lhic.11;I 1rii11eli/;tl.tl cxhibitctl tl.r~etel.l.itol.iality, ;In ;Irca oS 600-900 squ;rre feet. The soci;rl Iiic~-;r~.chyin Agccr~rc~~~;~r.tic.~~l;rrly in\~ol\~etl the Scm:rles. Ncver was ;I tlon1in;rnt I'cln;~leol)sc:~.vctl to lca\.c the clolnil~;~ntmale li/;rrtl with wlric.li slic w;ls ;rssoc.i;~tetl. Dcscr.tiolis by sr~l)ortlin;~tcferli~tles wcl-c co111111011. As ;I fill;rl poi111 1 ~ol~l(llike to s11.c~~tl~e I';I(X tli;~~tlic stereotylw(l ~IIS~I-U~Ior I)ol,bing I)ell;rviol- ;~lltltlic ;rggl-essio~i;111d (o111.ts11iljce~.c~~lo~iies of I~L;II.(Iswo111d 1e11(1 tlielllsel~esnicely to clrt;~ntifieatio~~;rntl c.ompoliellt ir~i;~lysisthi~t h;~s ~)ro\:c~i so rlsefr~lirl str~tlics01' fisli ant1 1,il.tl 1)ehavior. \4Tc still Il;r\,c IIO inl'ol-m;rtion of' ~vhicl~;~sl)ccts of tl~escI,eh;r\.io~. ~);tttcl-ns lniglit I)e ilnl)o~.t;rnt ;IS isol;~tirrg ~liecli;r~iis~ilsSol. li~;rl.tls. Fol- sollie beIi;r\~io~- I);rtterns, c:.g., II~I~I-II~)~,t1icl.c is yet no c1c;tr evitlence of the 1'11nc.tioll. '1'1-i~: ~)AII.~.~'I~:I (I;ry tl1i111:111ot IICI., 01. i11.e (.o~iij~lctcly~~r~;~\~;~il;rI)lc 1'01. ( ;I~I II~C ;it cc~.(;ri~i tirrics, rls~~;~llyat ~nitltl;~y. 111 solrle ;rI.cas 11t:rs, too, :11j1)t:;r1' to I)e ;rbse~itirt c-cl.t;rill ti~l~csof tllc tl;~y,hr~t this is not the c.;~scin T.\Jestel.llTcx;ts. Some I.C~IOI-tsof lizirl.tl 11e1-iotlicitymily ;rlso Ijt I~asetlrlpon the ~~e~.iotlicityof the itl\~estigalol.swho thoosc ~iotto hc ill tl~eficltl at tel.t;rin till~es.11-win (l!)(i5) tlclnonst~-;rtctl that 111;rs;II c c ;II.I-Y illg OII SOI~~C;I k)o\.e-g1.01111t1 ;r(.livity ;it evc1.y Iio~~r01' thc tl;ry, altliorlgl~tlicy ;rl.c ~.el;ttivclycjl~iesccnt tlr~riligextl-c~riely hot pel.iotls. 01le of the l)rol)lc~lisi11 st11tlyi11g])e~.iotli(ity lies ill oI)tiri~ii~~g.;I 11;1sis I'ol- c.o~nl);wiso~l01' ill(. IILIII~~):'I-01' li/;lr(ls see11 ;I( c;r(.li 110111. of t11c tI;~y I)cca~lscclI'o1.t cxl)cntlctl to c.;tj)trlre 01. sigllt the li/;~l.tlsIrlay I)c co~icc~lt~~atc(l;kt c.el.t:~iliIior~l-s. l<:;rc li tilnc \\.c workc(I ;I s~II(I~;II.C;I TVC ~.e(o~.cIe(ltlic tot;rl tiinc recltri~.e(lto c.o\Tcrthe ;ri.e;r, tllc 11~1111)e1-01' ~)col)Icin\201\,etl, ;rlitl the time ;tt whicll e;~c.llc-;rl)tul-e \zri~s11i;rtle. T'licl-cl'ol-c, tlat;~wc1.e a\,;ril;rl)lc to c;tlc111;rtc the ~lu~nbcl-of lninl~tcs tlii~t ;I li/;~~.tlM~;IS st1l)jec.t to oI)sc1.\~;1tio11ilt ;illy Iio111. of the tlay. Irom sl~c.litlat;~ I Ii:r\~tlctc~.tni~lctl tile 11111rll)el.of li/it~.tlc;rplu~.cs 1)cr unit ell'o1.t (nrirn-l1o111.s)Sol- every 11o11rof' the tlay. 7'lie d;~tafor botli stutly arcas I1.olri June, I!Hi l , till-or~gli Atlily, 1 !)(i5, h;~\,ebeen 1111npetl into two seitsons ~lliiclll.el)r(?se~~t, i.or~gl~ly, (lie 1.~1)1.ot111(.ti\'~;11it1t1o1i-rc1)1.0(1t~ti~e sezrsolrs (1;ig. 7). 7.11~tl;~t;r for .-\l)l.il to Sel)telril)c.~.tcl-t:~i~ily iritlicatc. ;I tlec~.c;tseill the 11trnll)er of c.;rl)tIll-es t1111-iligtl~c ~lli(l(lle of tl~etI;ry as well ;IS vel-y e:trly or very 1;lte. tIoweve~-,tlie 11111nhel.ol Ilorlrs tle\.otetl to capturing 1iz;rrtls at LIFE AND ~EMOGKAPIIY01; IJTA 8 9 PI(..7. I'criotlitity of 111;ts.A1)sciss;r sl~owsLilrrc of (lay fronl 7:00 A.M. to !1:00 kl.nr. I.cft ordinitlc is IIIIIIII)~~. of c.;~l)turcs(huntlrctls). Right ordinate is numl~crof man hours. The I)otton~I~islogt.;r~n is for tl~c],c~-iod Al~ril to Scptctl~bcr,the to11 October to March. I'igures al,ovc c;~cl~I~isiogl-a~n ;ISC nul~~l~crsof liz;~rtls cal>tlcl-ctl l>cr Inan I~ourof elTort. Banded scc~ionsof Iristogran) rc.\)rc.sent total Ii1al) lror~rs;cle;tr sccrion, nt~n~l,euof lijards cal,turcd. these times is col-resl~ontlinglylow. Tllc cfliciency with which ut;~swere captllretl (the catch per unit effort) was higher at initltl;~ythan at ally other time cxcellt late evening when the conspicuously incl-casetl ;ictivity of the lizartls ir~i~tlethen1 easier to 1oc;rte. 7'1ie tlata fol. Oc.tol)el- to March intlic;rtc that li/;ll.tls ;II-e solnewh;~t inore tlillic.t~ltto c;iplure ;~tthis season. 'l'his is bec;luse of their increased waritless ;it low aml)ient temperature; also, l'ewei- are seen ;~ctiveat ;my 1~11-ticula1.tilne. C;rptures belore 9:00 A.M. ;111t1 i~ftcr(j:OO P.M. were exceetl- ingly I-;I I-e. These data show that iL perio(1icity is clelinetl siml~ly21s I~cingexllosetl to observation or c;~ptllrc,there is little tliKerence at tlilferent times of the tl;ly. \i\i11;1t these data (-annot show is what tlifferences exist at tlilrerent liot~rsin tllc rlcgrc,e of ;ictivity. Suc.11 tlatii ;ire av21ilablc 1.1-om Irwin's (l!)(i5) paper Ix~setlon 32 1i~;rrtlstllit~ were watchetl ;I total of 200 1iol11-s over a periotL ol 57 clays ill the srtrnmet- of 1963. Tlle distance that each lizartl moved is shown in ;i soiriewl1;rt tlilI'el-ent lorn1 from that usetl by Irwin (Table 24). The fignres shown were cxti-apolatetl lrom Irwin's graph ant1 arc ;rljl)~-oximateThese tlata tlo indicate a I-etluc:tion in Inovcnlellt at mitltlay. Apparently, rnalcs incre;rse their activity earlier in the late aftel-noon than tlo females. ?I'he arc;^ occupiecl by an aninla1 and utilizetl in its search for footl, for mates, ant1 for shelter has been generally c;~lletlthe home range. The term has been redefinetl in \lariot~sways and e\,cn broken into components .\I1 I~~rlres;r~c I~IC;III feet pel hour for scvcl.; - . - -- .. -- ~.- - lMca11 fcct per 1iou1- IIot11. -- --- ~-.~ ll;~lcs Fe111;ilcs -- -. - ~ ~ - 8-9 i 3 34 0-1 0 (i0 4 7 10-1 1 53 3.1 11-12 75 24 12-1 58 30 1-2 2 I 1 5 2-5 I I 13 3-4 56 15 4-5 (Xi 19 5-6 1.11 3 1 (;-7 1 ti7 54 * 7-8 -13 7 3 suc1-r as an ;~cti\rityrange 01- home realm. Stutlics of horne range are impor- tant ill indicatirlg the si~cof area necessary to sustain an individtial; the degree 01' ovel-lap of Ilome ranges ir~clicates something about the soc:i;rl structure of the pol,ul;rtion. T would like to make it quite clear that thc Fact that tltas clelentl their entire area of familiarity makes it possible to use the terms home range ;rntl territory interchangeably when speaking of utas. It apparently is true 111;rt some pol-tions of the home I-;rrige ;rye Inore vigoro~tslytlefencletl th;rr~ others. It is robab ably the sile of tllcse vigororlsly tlcientletl ;r~-easthat sets ;I limit on the extent of the ~jossiblc compl-cssibility ol individtlal territories. Throughout the ensuing tliscussions I have used the term home range for the activity area of the utas even thotigh this entire area is evidently defendetl. There is no doubt of the importance to utas of the home range or of the re;tlity of such ;in arca. I'he lizards seem to know rather precisely where rnarnnlal btrrrows, packrat nests, ;rnd other refuges are located. On several occ;rsions we have purposely chased utas, attempting to tlrive them into ~rnfainiliai-are;rs. This is tlilficult to accomplish; the utas are more likely to tlouble back towartl the pursuer than to move into ~uilfamiliar areas, par- tic~llarlyif such a move involves traversing an open area. How the lizartl becomes familiar with the I~ountlariesol its home range seems ;Ipp;rt-ent from the data on relative moverrlcnts to be presented later. The distance that a lizartl nlovcs is directly l~roportionalto its age. Hatch- lings may be found for several weeks no more than a few yards from their hatching site. 7'heir moveinents ant1 the are;i with which they are thorolighly lamiliar incrc;rsc ;IS they matrlrc. This grad~ralfamiliarity with the area must be impor~antin avoitling enemies and in contentling with other utas. The establishetl resitlent, as we have already scen, is at a decided advantage. llespite the al)p;uent reality of the home range, it has proved difficult to me;rsure it accurately; this has ;11so been true with other vei-tebrates. Some of the clilIic.ulties encottnteretl wit11 the utas are as follows: 1. 'The li/ards tend to confine themsel\~esto areas muth smaller than the home range. Unless a very large number of recaptures are obtained, almost. a11 captures will be made in the srnaller arca and an underestimate of home-range si~ewill result. 2. The home range is soinetilnes shifted. This is obvious when a lizard has been capturetl several times in a certain area antl is then captured sevcral times in a secoutl ;ire& without returning to the first. Shifts by adult animals occlri-, I~utmost shifts take place between the time a liz;rrtl is young antl the time it mat111-es. 3. Malcs are much more active than females, so thcre is a greater probability of catching them at all points in their hoinc range tllan is the case with leinalcs. 4. Sonlc ;unimals occur at thc margins of the study area with some captures within the area ant1 some outsicle. The home ranges oC such animals are ;rlw;tys ltnclerestimatetl if the hulk of their home range lies outside of the area no matter how many recaptures may be made of them. 5. Lizards are less active in the winter and early spring than at other seasons. This makes it cliffic~rltto compare the home-range size of a lizard with numerous c.aptui-es dlti.ing the winter with one whose captures have been made 211 another season. Hec;~usethe home range is of primary importance during the breeding season antl because this season can be rathcr clearly clefitled, I have used only those c;~l)~~~-csm;~tlrtl~~ring rlle b~.c.ctlingsc;lsol~ lor con~l~l~lingIio~nc- I.;tnge :tr~tl for making co~nlx~risonsbetween tlillc~enr i~ltlivitlu;~ls.'Thr 111-ectling se;1so11 covers the l~eriotlII-OIJI R/l;rrch lo Sel~te~nber;~ntl is the pcriotl when our rec;ll)tllre clata ;Ire l~;rrricr~l;~rlystrong. I h;tw also con- sitlcretl only :~elr~lts01' 111-cetling si/c a11tl only rcsitlcnts of' the stucly ;tl.e;l (3 or more t.;rl)tu~.cswitliinthe area) 1 li:~\zc cli~nin;l~tttl11.onl co~lsitlc~-illion most m;lrgin;~l;rnini;~ls ;IS well ;IS a11 hose I-cc;ll,tul.es Sill1 on or neal- ;I straight line. rll'ter all of these climin;~tio~~s,1 ;in1 still lcl'r with mol-e t11;111 300 li/;~~.tlswit11 ;I 1ne;In of I0 re(-al~tul-csc;tcl~ o11 \whic-Ii to 1,;tsc ~llyestinl;~lcs. - - ~ .\rc;c I ------Sl'llcs S l~cl1l;llcs - -- ~ - I Olio i() 11 78.5 ( li) I !)ti I ,1221 (10) I(i XSl ( 7) lOij2 5,118 (IS) IS 1372 (12) IOli:1 (7) I0 34(iO (I,I) I!lli4 I I $3( I I) 22 975 (10) I !Mi5 lll2) 7 2fiS9 ( !I) :IY<) . 0 1 7!l 1161 (10) ; LSTIMAI.ION131, MINIAI~ILIPoI.Y(;oN.-~~~ plotti~~g ~111 of' tllc (.;I~LII~CS011 ;I g1-;111ll ;111t1 c.oiltletting the oute~-nlosLpoints one c;rn f'orm ;I l~olygon ;~rolinclthe ;t1.eil ill wIiic.11 a11 of the rccal)tul.es were mntlc. Tiilkle ci rrl (l!)(i2), ;iI'ter only one summer of wol-k on one ol' the st11(1y ;u.e;rs, estimatetl the si~eol' the Ilo~ncrange ;IL .O(j ;111(1 .02 ;~c.rcin :rtlrilt ni;~lcsant1 fem;~les, 1.cspec-tively. Tllese figures were 11;rsetl upon I5 nl;~les;~ntl I!) J'cmalcs c;~p- rr~retl;III avcl.;rge of 5 tinles each. Now, on tllc basis of 1/13 males ant1 171 I'cn~;~lcswith all ;lvcr;tge 01' 10 ;III~~!I c-;rpt~~l.es,~.esl,cc.~i\~ely, I cstim;~te the si/c of the honic r;tuge ;is .I I ac.1.e 101. ~l~:rlcs,.03 fol- fc~nl:~les. 'l'he 1.esults Y;II.~witlely lor cliff el-erlt yc;tl-a (T;rl,le 25) ;tntl be;w I~trthe~. tliscussion. One of the factors tl~atmight ;rlJ'ect liome-range size in utas is density, Sol. home-range size will be cornl)rcssctl wl~en tlcnsity is lligl~, exl);ti~(leclwhen it is low. Obviollsly, the relationship cannot be perfect bec;r[tse of the consideral)le o\rerlal) of lloirle ranges. Also, it inight be asked how tlle 1iza1,tls;tre aw;ti.c or the change in tlensity. This is a simple matter; the li/;~i-ds;we ;tlw;tys ~rloving;rl~out the margins of their home ranges. If ~rnc1l;tlIengctlthey will g~.;itluallyincor1,or:rte more area. In males (Table 25) the relation ol density to home-r;rnge sire is not ;it all clear. 'l'llis may I)e I,ec.;u~sc the grc;ttei. movelrlerlts ol the inales ztntl tlre gre:tter tleg1.e~of o\rerl;~l,ol their hon~cranges comparetl with Sem;~les le;t\,cs little :u.e;t Sol- csl);tnsion du~.iilgti111es of low de~lsity.Females, oil the other 11;1ntl, (lo i11tlic;rtc ;I cle;ti. inverse re1;rtion between home-range size ~ntltlensity. 111 both sexes tlle i~lterl)ret;ttio~~is cloutletl by difl'erences in the ;tver;tgc nu~rlberol c;il)till.es 1'1-0111 year to ye;ir. If the resources ill e;tc.ll stritly area were randomly distribr~tetland each li~ai.tl were ccju;illy ;~ggressivearitl no11-ovcr1;rpping in its ~~lovcments,a hoinc-1-;111gesi/e ol .I l ;~crcworlltl ;tllow about l!) resident males on or~r 2.O(i-;t(.1.cstr~tly ;irc;rs. This is higller th;tn tlensity estirn;rtes l~resentetllater, 1111t i~ltlic;rtestI1;tt estilt~;ttcsof si/c of home r;tnges :rrc reasonable if inex;ic:t. In ;tlly evcnt, few co~lc.lr~sio~~s(.;ti1 be tlr;tw~~from the estinlatcs nor do they h;r\~c1" etlicti\,c value. E:SIIM~\II 1:igurcs arc ill sclllal-c feel; IIIIIII~)~I01' loc;~tionsusetl for each estim;~tc-ir~ parenll~eses I 1;1(:.8. Ilorlic-range si7c of feriiales. Al~scissashows Iiome-range size (milrimurn polygon) it1 ~lious;~tltlsof square feet. 7'11c ordinate shows tllr nulnber of cal~t~~res011 which each esti. niate of sire is 1,asetl. No intlivid~calscaptu~.ed fewer than three times were used. I1 only the 59 lem;rlcs ant1 57 niales .cvith 11 or inore captures are con- siderccl, ;I me;tn 11onlc-1~:tngesi/e 01 2300 squ;tl,e feet (.05 acre) for females itntl (i310 sclr~;~rcfcct (. 15 ;tc.~.c)for nl;lles is obt;linetl. 'l'lie clifferencc of about 3: 1 ill the ~.cl;ttivcsix of male: fe~li;tlcIronic range is still e\~ident. 'I'IIE HOMI.:KAN(;I,: 01: ,]~IV~:NII.I~:S.-~~is tlillicult to capt~~i-eyoung utas eno~~gliti~~ies xvllile tllcy ;Ire still sni;tll to obt;tin an accttr;rte estimate of tl~eil-Ilo~nc-~-a~ige si/c. ,\ltcr they :u-e ;111out 11;tll-grown, antagonisnl between the111 ;tnd with tllc ;ttlt~lts,;IS well ;IS their own energy tlenl;tntls, lorce llleni to move ;tl)out nlore :t11(1 to cxp;ttitl their home ranges. During two years of this stt~tly;III ;itlelrll)r wits in;ltlc to c.;tl)ctlre III;IS f~.eq~~cntlybetween the [ill-c (:I llitrcl~ingit11t1 1l1e ;~(~;tinnlc~~tof ;I si/c 01 35 nun. Itt~~smucllas only al)ottt (iwceks arc t.cq[ii~.etlSol. g~.otvtllto tllis si/c, we were ~tnxbleto obtain ;I 1;tl.g~nl~nlbcr of c;11)tt11cson L~CIII.IIowevr~., we were able to obtain an ;tvcr;tgc of 4 c.;tl)tu~.csc;tch on 151 iil;tlcs ;untl 2O(i leriinles which indicated ltomc Ixnges so c-orisistent iti six t11;1t 1 (lo not 1lesit;tte to use such t1;tta. By nli~iinit~iiip01ygo11 tec.l~~~i(lt~chome Ixngcs of ilitlivitluitls oi both sexes were cstimatc(1 to be abot~t1300 sqtr;tre leet (.003 acre) in itrea. 1'11~following conclt~sio~~sc.;tn be clr;twn lroni the clata presented on Ilo~ne-~.;rngesize: 1. 7.11~I~onrc r;tlrgcs ;rl.c alu;tll conll~;~rctl\villi tliose of nl;tny other 1i~;tr.d~ LII;IL ha\,e been i~r\~estig;~tctl. 2. Tllc 11o1nc 1-:111gcs01' ~ii;~lc.;t~c t~r~clt~cstio~t;tbly larger than those of I'en~;tlcs. I. Aclt~ltsocx~11y lionlc r;tngcs t11:tt ;I]-e nl;lny tinles 1a1-ger than those ol ,~LIV(!IIiles. 4. Si/c of 1101ric ritnsc is higl~lyvari;tblc in tlillerent individir;tls initking the IIIC;III I~OIIIC-I.;II~~~si;le ;111riost ~lseless for estiniating nioveinents. 5. In c.oilti.i~stto \\rll:tt wits stittcd by Ti~lklc(,/ 111. (1962) there is consitlcr- ;tl)lc o\lc~,l;~l)oS tllc llo~neI.;trlges ol ni;tles, bt~tnot ol tllose oC lemales. iLl;tles f~-cclt~c~~tly1);lss within ;I J'c\\r feet ol one ;tnotlle~.in 1le;tvy vegeta- tion uritl~o~~lSCC~II~ e;~cll otlrer. Unlcss challcugetl, a male may wander cstc~isi\~c~ly;111tl ove~.I;~l)tl~c Ilonle I.;tnges ol atljacellt in;~lesin the pi-occss. ~I:SI,IM,\,I,I,:S01; 1 lo^ 1,: I Io.Ni~~etce~~ LIL'I~ (.II)LUIC~~ IIOILII 01 \tudy .tle,t I rvcle tlisp1,tcetl 300 Ice1 no1 tl~ol 111chi1 (,~pttil('lo(,~t~o~i. 1)~1111ig the 11cxt tl.tys, nonc8 IbOI< \'I\I Acre these lii.;trtls MJ;IS I-clocated,b~lt I'OLI~ oC tlle~nwere found on the fourtll day. All of tllcsc T4Jel.C nl;tles, ancl two were still in essentially the same area in w11ic.h ~.ele;~setl.011c of the renlaining two hat1 ret~~rnctlto within 25 feet of its origin:~l loc.;ttion ant1 anotllcr Ilatl movctl 200 Sect in the correct clirection. I l Irl- ANT) I)EI\IOGR/\PHI OF IJIA 101 ~~IO\~I.:RII~NTS01; IJ.I.As: I)Is'I'I\P\'cI- I%IT\$~I.:I.:N<;AI~TIIUES.-TIIC distance between captures MGIS c;~lc~rl;rte(Ito tleterniinc how close the nie;ul tlistancc betwecll cal)tt~~.csw;rs to thc 1ne;rn I.ec.al,tlIl-c 1-atlius ;rntl to determine wllethcr, ill tllc c.:~scof ,jt~\~e~lilcs,it ])rovitled another ~rsclulmeans of compar- ing re1:rtivc movements of 1il;rrtls oS tlilicrcnt size. 'l'he li~i~rclswere initii~llytlivitlecl illto I(i six classes, but in many inst;rrices tl;rc;r were i~is~rllicicntto (.ompare tlilfei-ent years zrntl areas. In ;rtltlition, lnirjo~.tlilfe~.c~ic.cs wel-c seltlo~nol)servetl, so tile data lor all years 11;rve bcel~lumpctl lo c.ornl):rl-e clilterent size gi-oups ant1 the data for a11 size groul)sl~l;r\~beerr ltr~ilpcdto coml~itretliIfci-cnt years. 'I'he coml~arisoi~ol t1ist;tncc I~etweencaptures lor tlilfereut si~egroups is sl~o\\~iiill 7';111lc 29. lhel-e arc only minor clifferenccs between the two ,['/IL! 1 .I 29 ])lSl,\N(:I I!! l\\zP.l~,N(~A~~I'~I~ s~~rcly;r~.c~;rs. 7'hc nlc;rn tlist;rlicc I)ctwccn c;rl)trll.es is bout the samc lor 17l;iles ;111(l I'CIII;I~CS rrtllil scx11;11~li;~~~rl.ity is ~.e;rchetl ;rl'tcr ~~llicllmales move about twice its I':II. ;IS tlo J'cln;rles. I;oi- 1)oth sexes, l~utp;rrtic~rla~.ly fol- males, the mean tlist;~nccI,etween c-:l])ttrl.es is 1;ri-ger th:rn the mean reci~ptui-eI-adius, wl~icliMI;IS 20:l ;111tl .37.4 I'ect Sol. fern;~lesi111t1 rn:rlcs, rcspecti\~cly.These data ;II.C co~~sis~cntwith those to be 1)resentetl or1 ~novcmentaway from the h;~tc.l~ingsite ill iutlicating :.:L gr:~tl~r;rli11cre:tse in movements as the lizard ilialm'es. Table 30 colill);~i-cstile inc;rll tlistaiice between captures in din'erent years, wlrcn stl-ong tl;~tirwere available. Little inlormation on relative move- meills ol jtr\lcnilcs is available 2tI'ter 19(i3. There are some obvious differences I !Hi I ,\r~vc.niIcs 15.9 (I) 15.0 (177) 12.3 (201) 13.0 (260) i\tlults 45.6 (14 1) 28.0 (I 1.1) 13.0 (144) 27.7 (IT5) belwcel~yc;rrs t1~1tl-eclr~il-c. c.o~~sitlc~-;~tio~~. FI'l~ed;rt;r sl~ow;In incre;rsc ill tllc nic;rn tlist;rnce between cirl>tu~.csovel. (lie tlirec-yeai- 11c1-iotl.For m;lles, the increase was slightly gl-c;itel- fron~ I!)(i I-l!)(i:! tlian Iron1 l!)(i2- l!)(i3. l'hc figul-cs in Table 31 show ;I ste;rtly tlcc.~-c;rscin \lei-y young ~n;rlcs(20-29 inm) on I~otlistutly ;rrc;~s.In;~snluch ;IS this gl.orrl> 1i;rs the sm;illest ;r\,cl.age 11101~c- 111crit one MJOIII~Icxpccl ;I (let.~-c;rsei11 tl)c nic;~~~(list;~n(.e 11et~~cc1i (.:II>~~II-~S IV~CIIthe ni;r.jo~.ity01' (:IJ)~III.~Su1c1.c 011 ;III~~I;I~S01' this (.lirss. 111 Ie~ii;~l(:s011 ;~rc;rI tl~cme;rrl tlist;rnce 1)ctwcel) t-;rl~t~~~.csMT;IS gl-e;rter in IS(i2 tli;rii ill IO(il, but tl~eme;tiis of I!)(i2 ;rntl I!)(i3 wet-c not grc;~tlytliflcl-ent. l'he figures in Table 3 I allow, cor~.espontlingly,th;~~ in I!)(i l 73 per cent of the c.:rl~tt~i-cs were of 20-29 niln Ii~;tr(Is;IS o11posetl to only 53 per cent in l!)(i2. 7'11~ 1)ro1>ortion of this siic (.lass ~.cl,rescritetl :rniong the c;rptt~rcs~l;rs ;iborrt tlic s;~mcin 1962 ant1 l!)(i3. 'I'lie tl;11;1 for I'cln;rlcs on ;lre;l 11 c;rnnot be ;rc.t.o~rntctl for so siinl)ly. The mean tlistancc I)ctruccli c;rpt~rresfor the tllree yc;rrs MGIS not grc;ltly different nor were the propol-tions oC 20-2!)-1nm yoling- for 1'361-62. Howevei-, in l!)(i3 ;I signific;rtitly smaller l)ro1)ortio1i of tl~cc.;rl)trrres were iriatlc on 20-29-1n1n ;rni~ri;rls; yet, this l';rct was not registel.ct1 by a signific;lrit c.11ang.e in the ~iic;~ntlistance between capt~ires. Another factor known to influence mo\.ements of 1i~;rrtlsis poprl1;ltion tle~lsity.Both sexes showed an incre;rse i11 mean tlistance bctrvceii captures I IFP ANI) I)E,AIO(,KAPH\ or II I A 103 1'1-o111I !)(il lo l!)(i2, 1111I 011 ;II.~;I 1 mo~-cc.c~.t;ii~ily t1i;in on Area 11. The tlc~~sityof jr~ve~lilcs011 tl~ctwo ;u-eas was ;rbout the s;iinc in 19G1, bul c.onsitlc~.;il)lygr.e;kler ~II;IIT;~ 11 in l!)(i2. 7'11~tlel~sity on both areas in 1963 was highcl than tlic ~)i.cvio~lsyc;ir ;111d yet (IIC li~;irtlsSIIOW ;111 increase in 11ic IIIC;II~~~S~;IIIC.C I)C~WC~II (.;iptt~res 011 1)otll ;II- IS. 1)cnsity ;111tI S~LCoi' ilicli~~i(lt~;~ls;ire 1)rob;il)ly 11ot 1.esl)onsible Tor all of tllc tlilLcrc~iccs o11se1-vetl, 111rt tl~esetwo factors will ;~ccou~ltfor most of IIICIII.It is ;it 1c;ist tle;~~.tl1;it the c1ist;rncc bcwecn c;il~turcsis ~iscfulfor tlc1no11st1~;1lil1gthe gr;ttlr~;~li~icrc;isc in c1ist;tnccs movccl by utas as they 1~1;lLlll~c. 7'hc tl;~t;i1.01. ;itllllrs ;il-c ;ilso sliow~iin T;il~les2!) ;111tlSO, ;~ntl;~rc not c.onll)lic;t~ctl I)y co~~aitlcr;~t io~ls ol' si~cbcc;tr~se all of thc tl;~t;~;ire from scxr~;~lly~n;itrt~-c ;illi~rl;ils, so ;111 il~tlivitluals;ire ~litl~in;I fcw millimeters 01' o~~c;iliothe~- ir~ length. l'hc tl;~t;i Tor i~tl~rltsscclri I-c;~tlilyexl)lic;~l)le in tel-~nsol' density bec-;t~isc111c m;i,jol. in(-I-e;rses in the Incan t1ist:unee between (.;I~)LIII.CSot:cu~-yet1 in l!)(iS ;tntl l!I(i5, when he tlenaity oT ;~clultstleclinctl sig~iificantlyon I~othstt~(ly ;ire;ls. 7.11~tlilfcrcntcs, ;IS ;~nticilx~~ctl,were mol-c striking in n~i~lest11;t11 in I'~III;IICS,;11it1 111e I-C;ISOIIS for this Il;ive bec~ltlis- c-i~ssctlill clel;iil in l,~.c\rio~~sseclions. l)~sc:~rss~ow01 LI.I~II~,I~~III TJltr .sttrlr.sl)rrric~~rn(Jol.genso~~ ;111(1 'I';IIIIICI-,I!)(i:i): .lo, .03, .0.1 ;I~I.Cill ;rd~111. ~l~;rlcs,;rtlt~lt females, ;tntl J~~\zcnilcs,~.esl)ecti\~cly. 7'0 m). knou~lctlgcthese a1.c thc ot~lya~utlica in ~~~hithI~omc-r;~l~gc si/e II;IS bccn (letel-~ninetlfrom I';til.Iy 1;tl.g~II~IIII~)CI-S of C;I~)(III.CS.Sc~reral otller recol-ds, such ;IS r hose Sol. Molhrooltitr ~~rtrcrrltr ttr, Sr.c~lo/~or~r.sI~~I(~II/(I~IIS, (~71(:111i(loplrorr~.sgrr1(1ri.s, ;rtl(I (;. ~i~qri.s,I):rsccl LII)OII o11e or :I Se~vi1i(li\litl11;1ls (Milste;~d,1959, 19fil), S;tll within tlrc I.;III~~of \.;tri;rtioll 01 IIOIII~1-;111ge six I);lsctl on the five species lislctl ;rl)ovc. 'I'lle data on A7tr(,i1~1;~r~tl Rtr.sili.sc~rt.s, wl1icl1 i11t1ic;rtcI;r~.gc~- I~omc I.;III~CS for juveniles than i'ol. ;rtlr~lts,I)~;II- 1'111 tl~cr(list r~ssion. 'l'llis ~.el;rtionshil) I>c~wcenhome-range si/c of ;~tlrtlt;t11(1 jll\~~liilcII:IS ;11so IICCII I.~~)~I.Ic(Iby otllel- authors. I think in ;)I1 rlc11 c.;tscs rl1;rr wh;r~is c-;rlletl the Ilo~ncrange of ,jr~vcnilesis probably ;I c.onl~)osire01' ;rrc;rs oc.cl~~)icd1)); ;I ).o1111g;tllilll;rl :IS il tlis])el.ses, and is not (ornl);r~-:rl)lc~vith the honlc I-irngc ol it11 cst;tblislictl :ltIlll~. 'I'l~esix ol the hollre I.;tngc is ;rlnlost (.c~.t;ri~ll).;~ssoci;t~ctI wit11 dc~~sit);, rhc I)I'CS(~II('~I.;~bsen~r-' oi tcl-I-itori;rlI)cll;r\.io~., :rntl ~llcl)l.otl~~c ti\.ity of (11c Il;tl)i~;rt,;IS well ;IS with the tcclr~~iclr~c'tlsctl to rne;tsul.e it. 01-t1in;rrily all of tllesc \~;rt-i;tblcs;rrc not invcstig;~rctlin ;I single stlrtly; so lirrle can bc g;tinetl by furll~crconsitle~-;rtio~~ oS LII~ tl;~(;t ;~\,;til;tl)lc on home-r;r~igesix in tlill'ct.- CIIC sl~ccics. <:;rlcul;rlio~~ol home-r;rtlgc six 11;ts 1101 I~ccnthe most c.olnlrlon Ii1c:tns tlsctl lo III~;I~III-~the Inovelricnts of li/;r~-tlsin n;rt~~r;tl~~olx~l;rtio~~s. l'hc ;tvct.- age tlist;rnc.e between captr~~.cs01. the ;~\'et.;tgetn;rxi~llt~in (Iist;~~icc I)~CTYCCII c;rpturt:sl~;rs bee11 eml)loyetl n1ol.c c.omlnollly. l'he tl;rta on lizartl ~novclnents 11sillg tllcsc tec.hniqucs ;rl.e sllow~~ill 'I';~hle 32. :\gain, in inslxctillg ;tntl c.o~t~l~;tl.ingthese tI;rt;r, we ;IIT I';rc.ctl wit11 the l)~.oblemoS c.o~nl);r~-ing1ne;rs- rlrcnietlts 1);tactl 1ll)on \.;tstly tlill'crc~~t~~rrl~ll)c~-s oc intli\.itlr~:tls, rn;rjol. tlill'c~-- cnces in avcr;rge nl~~r~l)el.oS rcc;tl)~rrrcs,;tl~tl in tilrle illterv;rls he~wecn c.;tptures. LJntil it can I>e demonstratetl that tlic mean c1ist;iucc between c;rptr~resis not seriously aKectctl by the val-i;~bles above, in addition to I)ISI'I\N(:IK 1%1,:I'\VI>IIN ~:i\l'I'lJlll'SI'OK SIK\.KIIAI,SPECIES OF l,l/,,\Kl)S RI..I'~I(II..I)IN THE I.I'IFKA'IUKI( /'/1~~y1~0,~0~11~1..\i11/1ji~ 70 1'c.e~ fi,!l!l!(,i/,.\ //!.\( ;/ll!l,s 8 4 .l7--9I feet 9 T 11;-28 fret ill\. 15-82 fret P.'l!l!!ci1,Y fl/~,\~)/~/t1.\ tlcnsily, li~lc;~l.ityoC tlte h;tl)if;tr, ;tntl tccl~nicj~te~tsotl, 1 itl~tst(.o11(.llttle tlt;~t suc.11 i~ll'o~.m;~tio~l111;ry I)c ol' little v;tl~te. k1ov1,:hu:~~rI:I 1.1~~.XNI) ~)EI\I~GKXPHYOF IJTX 10'7 'l'lle Inovcrnent 11) very yo1111gI~L;II-tls (20-2) ln1111) is extl-emely low, averaging 10-12 Sect in both sexes. On this b;rsis, it secins very unlikely tl1:1t ;rplxccial~lciinnrigration into the stlr(1y ;~rc;~soccurs by ;~nimalsol hatch- ling si~c,it fact tIi;rt Iias co~lsitle~-;~l)lcsig~~ilic-ancc for tllc measurement ol ni~tality.1Sy tllc tinlc that they :ire ;111olrt one-h~ilfgrown, iildi\ricluals of botlr sexes halie t1isl)crsetl to ;in ;tvcrirge tlistancc of 25 feet frorn thcir Iiatching site. At sext~;rlin;~tl~rity, I'cmilles arc locatetl at all itvcrage tlistance ol' lil'ty I'ect Sl.on~their h;ttcl~i~~ghire, ~n;~lcsat (iO to 70 feet. Thcse figl~res rcprcscnt jmsl ;11)o11t two 1ne;llr I-C(;I~I~III.Cr;~dii or tllc ;~l~proxirll:~lcCOIII- p11tet1 tli;l~nctcroC ;un ;rYcr;ige i~tll~lt'shome range. These cl;r [;I illtlic.;~rct h;r t yol~ngli/;rl-tls est;~blisllhome r;lnges by con- tiii11:11 p~-obingillto tr~~l';~ri~ili;~r:IIT;IS :III(I g1-:1t111:rl inc(~rl~o~-atio~lof s~rcli ;rrcirs into their Ilolr~eI.;tllges, :I process tllat coi~tinuesrliltil cheil- 11onlc- r;lngc bor~ntl;~ries;Ire too large to tlel'entl s~rcccssfully,Honie-~-;~nge estab- lishment is not i11w;rys so siml~lc;I p~.oc.cssbec;~~~sc sonle of the ut;ls est;~blisll hornc r:cnges ;IS ;~clr~lt:,t11;1t tlo 1101, c\,cn i~lcl~ctlcthe arc;l tl~eyoc-c-~rpietl ils j~~\jcnilcs. 1-1 '11. .I .1s' (I !)(i,l) nl;~tlctllc i~~tel-csti~~gol~sc~.~:~tion 111;1t trll I~:~tchlingnl;llcs 01' /lgo~t~trcrgtrt~~cr Ic;~vc the ir1.r;ls tl~cyoccr11)ietl ;IS j~~vcniles,111rt yollng I'cm;~lcs111ay rcnlai~litntl c\~cnevc~lt~~;rlly mate wit11 the tloini~~i~ntI-esitlent nliilc in the sanlc ;~rc;~.The only otl~crt1;1{;1 on r~lo\~cnIcntsSrom the I~irtching site by lizal-(1s ;IIT those of J I)ISI.ANCII;I Y -u mnn 010r-r + GO- hla~-m+ w1.w Y *+? NCVN 4-- NNN W~LCwnn NNN - 4 # - II D 4- --n ~y?ql>q ?om. O+.q qoq q~q c .X 6oG nmm +~.m wl-m 2- ornm nnn nnn nnn 3%: %%$ ZG% .-- V1 -U4 > i w nmn 11 1 -33 NNM -3- n~nI-- ti E % 2 .d2 3 6 2 C? ? ? 000 mol? 009 001: 000 0 2 .X =ow II I *I.m mmo m-m w n;c-r01 n w, m nw,n nnn nan w,nm ~nm 2 2 6 E "7 A 2 2 z 2 nnn --- I I I II I mmo --m -r** 2 g % - - - ; E I'COO 0.00 , h 8 I I I II I ?Fa: ?c?- >=00 ,X &,&,< amm ocww cno~ 2 2 clmm wc 13.0 c&i *a* I I I I II NNN 1.1.w Oml. NN ZZY 7 NN- ICTCc. I W NV-.I ,- z3 0. 0 I^ I I I O.CX? "m,? ">CE, cq g 1 I I amm ITmm mcw z- I < Qi 2 n0m mnm mmc Nn 5 E 5 2z5 a2 'E;a -?4 2 C\I%~C\I IXP~I- nmn -rmmm 000 ~D~D~O 2 !& - N N N * w d 5 5 ;1" 991: qy~OI?~ ?ma LC?? oqo - x now nnm wmo 6 G-m 1.1-1- -OIM Ga 6 NN~mnn mn* w,nw, mwn nnw, mnw, + % a8; * z 4 9 w a c-cc-~m I 1c.w~ I.I.I. ,,, m n n L"M 8% - - - 2 8 ,. ffi E +- moo cay ?,P:I: qoo! o?? E:% %ma TI- mmw (11-K a1.a I ~mtc. C: ocein w,w,n nnn nnn nnw, mnn nnn I a, 01 ci aJ w C) cI u e - .- - 4- + 42 +d - w .Q u Gs? 2~2ga, 2s; ,,,EGG ,,zffi + 5 w ffi e h~ E L B Y) a,22g;:,,g~:,,;~;,5g~ QI' F zqg5, I~Gu~ '1'111,:(;I Air Cloaca1 Cloaca1 temp. Time to TVeight Per cent surviving temp. ternp. at start at end (CTXI) CThI (secs.) fgms) experiment Expt. 1 12 8 8 35.836.8 35.6-39.4 43.015.8 50-84 4.43 17 18 0 9 all 36.8 36.8-38.2 42.4-45.8 53-93 3.24 60 Expt. 2 18 8 8 14 0 P Expt. 3 12 8 8 31 33.g34.2 38.442.8 15-72 22-28 mm 58 (not \\.eighed) 13 0 0 31 33.6-33.8 38.0-43.6 20-65 22-28 mm 62 Totals 42 8 8 37.2 42.7 46.8 4.53 43 (adults only) (15 9 0 37.3 43.3 53.7 3.18 58 Time to panting: 16 seconds, $ ; 18 seconds, 9.Temperature at onset of panting: 37.3 8 ; 39.5 0. hantl constant exposure to very high temperatures through the summer in this area may be somewhat debilitating and partially responsible for their short life expectancy. Even at high air temperatures utas will be active all day if a cloud cover exists. 1r.cvin (1965) notetl that in 33 hours of observation on overcast clays between 1:00 and 5:00 P.M., inales moved an average of 127 feet per hour c.omp;~retlwith only 48 under sunny skies at the same time of the day. A few of the ~it;tsused ill the CTM experiments were staked on the sand when ;II~occ.asiona1 sm:tll cloud passed over the sun on an otherwise clear day. 1)cspite no signific;unt change in air or substrate temperature at such times, the retluction in r;ttliation was sufficient to lengthen the time required to reach (:131\/I to an average of alrnost 7 minutes. Obviously the margin of t11errn;ll s;~fetyis considerably cxterltlcd in lizards even on partly overcast days. TIIEI'IIERMAI. ENVIRONMI~NT OF TIIE STUDYAREAS.-TI~~ discussion of tllerlnal relationships of the lizards is incomplete ant1 inatlequate without some knowledge oC the tllcrmal environment in which they live. To indicate the temperature regimes available to the utas in various microhabitats at different seasons, continuous recordings were made of air or soil teml)eratl~res in vitrious parts of the home ranges. Air telnperatlires were recortletl with 7-clay Te~npscril)esthroughout the summer at a height of about 1 meter above the sand surface in the open sun. These recortlings show a regular fluctuation in the daily temperaturc I'rom an average low of 70" 1; at night to a high of 100" or above during the day. A sample of this record for the period July 6-13 is shown in Figure 11. 'l'llis week was chosen bec:t~~seit appeared to be intermediate between the hottest and coldest weeks cluring the summer. As the graph indicates, air tenlperatures between noon ant1 5:00 P.M. are somewhat above the preferred temperatures of the utas. It is the extremely high sand teniperat~~reant1 clirec:t insolation at these hours that suppresses lizard activity. 11s notetl previously, utas rarely retreat unclergrountl in summer during tile 11e;tt of the clay, but instead remain on the surface beneath the bases of yuccas or in heavy shade provided by mescluite. Simultaneo~isrecordings oS temperatul,es in the sh:tde at the base oS a yucca :tnd fi inches below the sand surf;icc adjacent to the yucca provitle an explanation for this behavior by the utas becalise the tclnperatures on the surface below the yucca arc lower than those in the sand (Fig. 12). Air temperatures in the shade of ;I n~esc~uite(011 the ground surface) or in the shade of a sage plant (on the ground surface) are consicler;~blylower than air temperatures ill ;III ~lnshacletl area (Fig. 13). l'l~ehigh peaks in the graph for the sage represent alternoons when the pre\~ailirtgwintls allowed the recortler to be unshaded by the sage. LIFE AND DEMOGRAPHY OF UTA I:I(.. I I. !\is tempc~.;~tuses(F) at 3-hour ititcrvals recorded i11 an unslladed portion of tl~eTcs;~.; sll~tly area at a iicight of 3 feet above tlie ground, July 6-13, 1962. Thrce figures sllow pertinent data on microclimatic conditions during [he winter. Figure 14 illdic:~tes that a lizard would receive little protection from colt1 at lligllt if buried in the sanie shallow fashion that is characteristic cluring the sunmer. On thc othcr hand, good protection is provitled by burial to 4 iachcs. Figure 15 shows that subfreezing temperatures (air) were 1'1(:. 12. Col~ll>:il.isonof tcln~)cr:llur~~sat surf:lcc ill slladc of y11~cns(solitl li~le)wirl~ 111osc'(i il~clrcsI)etrc;ltl~ llle surface of s;111tl ;itljaccrlt to lllc yucca (broke11 line), June 2-!), l<)(i2, I<:i~-ly1);u.t of ~.ccortlII~;I(I(. tluriug ;i 1)eriod of ovc.rcast ski(,s. L)ots on 111(. record arc ~)I;~ce~l ;it :I-l~oul.itlle~.v;~ls. 1.ecorrlccl every ~iight,1~1t the sand temperalure never fell below 36" I;. Tllis tlcplh (4 inches) is about tllat from which most lizards 11;1ve bee11 coIIec.tct[ (It~l'i~lgthe wi11te1. I'ro111 the sites ol' their periotlic quiesc.encc. Fig.111-e I(j, lil~;tlly,sllows 111a1 clespile the concentratioll of lirartls ;II-O~III~~p;ickr;~t lle~t~ I'rc:. 13. C:tr~r~l>a~-iso~lof :I~I- tc~~~l)c~-at~~~.cill SIIII (It.ft. solicl) wit11 t11;11 at S;IIII(.I~cigl~t (3 feel) in sl~;~dcof ;I mcsquitc. tl~itket(solitl, right) :inti on the SIII-~;ICC bc~~c;~llr;I lal-gc s;~gc 111;tnt (I-ight,1))-oken). July 5-12. IINi2. 1)ots on the ICLOI.~ ;IIYat 3bi1011r~I~~cI-\J;IIs. in the winter it is probably not the nest itself tlxtt 111-ovides shcltcr fro111 the colt1 but r;~thcrthe loose santl arountl the ~lcstinto which the II~;IS burrow. 1111 of tllc figures show that Savorable tetn1,er:tturc I-egimes can bc fount1 in tlle 11al)itat; this, of course, is obvious. I'he clata also show ~lhy certain plants or certain sites or cci-lain tlcpths of' l>~rri;rlarc prcfei-retl by the ut;rs. NATAL,ITY.--~~~I~1)il'lll rate of 11t;ls was tlilfic~lltto (leternline in ancon- fined ;tt.e:ts. All young lizal-cls inarketl [luring c;tcli rcl~rotluctivescason were co~rntedas protlucts of the adults of that generation to obtain maximum estimate of natality. A more conservative figui-e was obtained by considering tlie j~~venilcsm:t~-ketl during June to September as young of the year. Some FIG. 14. Coinparison of air tcmpcrat~n-c(solid lirlc) with temperature 1 inch below thr sr~rfacc(broken line), I)ecci~ibcr16-22, 1961. 1)ots 011 the recortl arc at 3-hor~riiltel.v:rls. 1;1(;. 15. Cottlparison of air tctnpcraturc (solitl linc) abovc groutltl with that in an ;(I-tificial bun-ow 1 inches helow rhc sand sr~rface(broken litic). I)c.ccllrt,er 22-20, 1961. Dots oli tl~c~.cco~tl arc 211 3-llortr intcrv;tls. 1'1c. IF. Comparison of air tcmlxratnrc (solid line) al)ovc gl-o~~ntlwith tellipcratuvc: inside an adjaccnt packrat nest I>cneath ttrc sul-facc rovcr, br~tno( in a 1)urrow (broken line), Novenlbcr. 18-25, 1961. I)ors and tl-iatlglcs on the rccortl arc. at 9-lrol1r intervals. I.IFE AND IIEMOGRAPHY OF UTA 121 new utas wele marked throughout the fall, winter, and following spring. It was not always clear that these animals were produced by the resident adults; many may have been immigrants. During June to September the areas were worked intensively and we generally were able to mark the young lizards soon atter hatching, so I feel that the conservative figure for natality may be more nearly accul ate. It is best to recall that the reproductive potential per female, as esti- mated by the lnethods discussed in the section on reproduction, was about 12 young per female per generation provided she survived to produce three clutches. I pointed orit that this figure of 12 young per female could be an underestimate. Tlle data p~esentetlhere on natality and later on survivor- Scc text for a disrr~ssio~~of the t~\.ototals . ------Conservative Year Area M;tles Fe~nalcs Total Total - l!)(io I no * 94 * 184' 175* I I - - - - 11161 I 239 216 455 378 I I 225 264 489 430 1962 I 125 113 238 212 I I 189 192 381 300 1963 I 147 171 318 307 I I 243 255 498 459 1964 I 127 142 269 237 I1 155 155 310 277 * Figures incomplete; all young not ~narkcdthis year. ship also provide evidence that the reproductive potential was under- estimated. For this reason I have not chosen to use the data p~esentecl eatlie1 on reploductive potential to determine the theoretical natality, but have relied instead on figures of the actual number of young lizards marked each year. The natality figures, based upon total numbers marked and on the conservative estimate discussed previously, are shown in Table 36. The natality has varied by almost a factor ot two ovei the several years of this stutly. Some of he changes, to be discussed later, are attiibutable to radiation effects, but others are not. One of the factors responsible has been a change in the number of resident adults from year to year. Data compar- ing the natality with the number of resident adults are shown in Table 37. ------~- .. - ~ X11111l1cr So. young/ Yc;rr i\rc;r Rcsitlcl~l h';~(;ility rcsitlcnl - ~ -~ - p----. . - I!K 1 I 19 37s 20 I1 25 430 17 1!I62 I 22 212 10 I I 25 300 1 3 1!)63 I 10 30; :\ 1 I1 17 45!l 27 1 !I64 I 23 237 10 1 I 33 277 X i,> 2 1 325 15 Bcc;rt~sethere arc sevei-;tl ways of estimating thc nrrinber of I-esiclent atl~~lts, I have c11ose11 tllc figures I'or the total numbcr of ;~tlultsthat were rcsitlents of the stlltly ;u.ea at anytime SI-om I\tl;ircll to August, i.e., anytime tluring tile I-eprotluctive seirson. These fig~u-escle;~rly intlicatc th;rt each fenlale is, oil the average, 1)rotltlcing Illore t11;in 12 ollsl)ring pel- generation. Natality is gcncr;rlly lowest when ;ctl~~lttlel~sity is highest, I)ut the I-elationship is certainly not a straight linc. For ex;~mple,19 fem;~lcsill 1961 l~rotlucetlan i~vcr:~gcol' 'LO young each wl~ile17 in I!)(iS l~rotlr~cctl;un average oE 27. Tl~ese figures arc somewllat surl~risingin view of the fact that conservative figurcs for natality have been usetl; they suggest seve1.;11possibilities: 1. Many fern;rles fl-om orrtsitlc sometimes lay eggs insicle the study area. 2. Many, if not 111os1,l'clnales 1;ry I~IOI-et1i;rn 4 tlutc-hcs. 3. Many I~atcllli~lgsirmnigl.;~tc to the study i11-c:rs shortly ;it'ccr hatching. Non-resitlent l'em;rles we occ;~sion;rlly c;~l,turetl insitlc the study areas tluring the breetlil~gseason. That these might be transients seeking nesting sites ill the area c;ulnot be ruletl out, but it seenis unlikely to me that fenlales :it the critic;rl time of egg-laying ~~oultlleave irre;ls with which they were familiar in order LO tleposit eggs. Yet, such behavior has been reported by Blair (1960) in Scelofior~isoliuccccrrs. I think that sonle females simply lay more tlutclles of eggs. They ;11-e c.;tl~;rl)lcof doing so in the laboratory, ant1 one OF my former stude~~ts,C;er;rrtl Hotltlenlx~t11, has informed me (i~rlitt.) that he has solitl cvitlenc.e Sol- the protluc-tion ol as mirny ;IS six clrrtthes in ;r single season by some Uta sta~rsburia~luin Nevatla. Finally, there is sorlle movement of young utas into the study areas, but rny data indicate that this wo111tl not account for the tliscrepancies between calcl~latecl and theoretic:~l natality. All three-nesting .. by. non-resident females, underesti- malion of tlic rcprotluctive potential, ;untl inllnigration-play a part in making the natality estimates inexact. 'I'inkle r,t 111. (l!)(i2) st:itetl their belicl' tll;~tthere is little 1)rehatching n~ort;rlityin Illn. With he exception ol thc two years when lizards on the stutly ;u.e;ls wcrc ri~tliated(Area I, 1962; area 11, 19(i4), the number of young per female has equaletl or exceeded the n~~mbcrpredictetl from data on clutch silt or clutch frequency. If the fcmales on the sttidy areas were pro- (ll~cingmore than three cl~~tchcs,as the tl;~t:~now intlic;~te,then my opinion on the 111atte1-of 1)1-~11;1tchillgmort;~lity might I)e altered. hltllo~~gh1 have iitteml~tcdto measure natality by marking the juvenal lim-(Is :ISsoon after hatching as possible, 1 h;rve p1-011;~blyfailed to obtain a11 ex;rct ~ne;~sul-cbecause the cleat11 I-ate im~necli:~telyafter hatching is so higll th;rt it is simply impossil~lcto register a11 the hatc-l~lingsbefore some of them tlisal~l,c:tl-frorn the popu1;ttion. Even so, it is clear that the average number of 35-40 rcsitlcnts of the stl~dyarea co~~ltlbe maintained with only ;tl)orrt 15 per cent st~rvivorshipol hatchlings to rnat~~l-ity,provided that there w;~slittle mort;rlity of :~(lults[luring the breeding season. It is unfortunate thal the tlata most lieetletl to c;~lculatenatality are tlre very ones most frequently ina available For n;rtr~r;rlpoplllations of lizards. The ncc.cssary data arc the knowletlge of age ;II maturity, the age-specific fertility, ant1 the tlerlsity of l'cmales. These tl:~t;~are not available for any sl~ccicswith the possible exception of Scc1oponr.r oliucrc.elrs. I'he work of 1ll;rir (1960) mlrst bc regartled as exceptiollal in this regard. I tllink, as stated previously, that even with fairly good data I have undcrcstimatetl the repl-otluctivc potential. This must be obtained in future strltlies by an;~lysisof large salnples to (letel-mine the cll1tc.h size irnd seasonal ;tntl :~gc1';~ tors that affect it. The number of c-lutches lnllst be determined by c.al>tiwing the same sclectetl females at 2tbout weekly intel-vals for palpation (171d 7(1(!iglii11g.The loss of weight at the time of oviposition is so striking that the number or layings coultl be accurately tletermincd. This procedt~l-e coultl bc (lone more sinll~lyin the l;tboratory, but I doul~t,in the present state ol' otll. knowlctlgc, that this woulcl be 111e:ulingf'ul. TIIP:ESTIMATI~ OF CRUIESIJKVIVORSHIP.-T~I~ major assumptions that must be made in estimating survivorsllip are that a11 nlarked ;~nirnalsare cvcnti~;~lly~.cc.:~pr~tretl :rllcl, if not, that they ;ire no longer alive. Both assump- tions are ol~violtslyinvalitl, but our ~netllotlof se;n-ching beyontl the boun- daries of the study area lor emigrants and marking large numbers of lizards over several years helped reduce the error. Animals that were never recap- tured after tn;~rkingwere not r~setlin the survivorship estimates. 'I'ittklc (lS(i7) 111.ese11tctl tl:rt;c (XI s~rrvivo~-shipol' III;IS which ;ire shown ;rg;rin in Table 38. The tlata show great consistency in the l)rol,ortio11 of atllrlts of one generation that .survive to the next 111-eedi11gseason. Hecause the atl~tlts;tvei-age about !I moriths of age ;it tlie onset of their first repro- ductive se;tson, it follows from the data it1 I';tble 38 that the ~)rol~ortion reachirlg 21 ~uot~tl~s01' ;tgc is rill-ely above 10 pc~'tent. 7'0 1)11tt11e m;ttter tliffererltly, there is itborrt !I0 pel' cent turtlovcr of ;r(lults each gcncrirtion. The figure on srrrvivorsllip of juvetlilcs (Table 38) is less satisfactory than th;tt for adults for the following reasons. By the end ol each fall we hirve I-egistcretl SO per cent or more ol the young l,rocl~rretl on the study (:UIJI)I SIIUVIVO~~SHII~01:A~)LII I ANI) ~UVI:NAI.11.1~s IN I, IVI,: YI,ARSON 'I'wo S~[JI>YAUFAS - ~ ~ ~ ~ ~ ... -. I 960 I!)(il l!)(i2 1963 1964 .Irca 1 11 I I I I I I I 11 I I I ------~. Total ;~tl~tlts 46 - 6.1 72 51 (i-l 30 57 81 110 ing to next Sc;~SOIl n -- s 10 T !) x 11 6 9 areas, I>ut there are ;llw;tys ;I Ccw immig~-;t~~ts;is well ;is ;I few jrrvcniles that elutle cal~ture. (;onscclr~ently, IIII~~I-ketlli~;r~-tls arc occ;~sionally fount1 (Illring the winter ant1 lollo~virigspring, which may or Inay IIOI be young ol the p~-eviot~ssummet-. 111 Fl';tl>le38 the cl-utle srtrvivorsllil~data for juveniles inclutletl these question;rble young 01' the year, but inclusion ol tllein biases the survivorship data because (1) they may not be young of the year; indeed, they may not be yotrng li~artls;rt all; (2) the survivorship of these anim;~lsis generally ;rss~tretl becir~~sethey 211-e of tle;~rly or at-tual atlult six ~vhcn marketl. To refine my cstini;rtes of c-I-~rdesurvivot-ship of juveniles, 1 here re- clcfine ;I young of the year ;Is ;I lizal-tl fi~.stn~:t~.ketl ;rt ;I six less t11;in six at maturity betwce~~~LIII~ ant1 Septeml,ei-, tlie n~o~~thsdlrt.ing which the study areas were work.etl intensively. T11e revisccl figures on juvenile S~I-vivot.sliip are sliown in Table 59. A jrlvenile was considered a survivor if it was reca~turetlat an atlult six ;tnytime aftel- the onset of the rel~rotluctive T IFI:. AND DI.:MOCRAI'HY01: I:TA 125 season. T'hesc data indicate a slightly lower stirvivorship than did those in Table 38, but both sets ol data show that srrrvivorship higher than 20 per cent is rare. The highest survivorsllip occurretl in tlle winter of 1963-64, which was an exceedingly mild one in the area (see section on winter kill), and let1 to very high numbers of ad~lltson the two study areas during the 1964 breeding season (Table 38). The survivo~~shipof lemales is greater than that of males. Tllis is consistent with the data on winter kill presented earlier ;ind with the illformation on age-specific rnort~llityto be presentetl later. ~1'41~I.E3!1 Rrv1sr:o I:\c.ti~esON C:RIIDI: S~IR~I~~~KSM~POF JCIVI,.NAI.LITAS ON T\vO AREASIN FIVEYEAI~S See text for discussion. Figures in p;u.entllcscs are Ixrcentages ------Juvc~lilesprod~rccd Surviving to ~natltrity 7'11~tl;~t;~ on survivo~.sliipof juveniles Ilatchetl in 10(i4 are particularly ilnportant because in June ant1 ,July ol 1965, at the termination of the field stutly, utas were killed ;lrountl both st~~tlyareas out to a distance of several hundretl feet in ill1 intensive effort to fintl emigrants :und obtain precise rnort;~lityesti~ni~tes. T'he tlata for 1964 were consistent wit11 those of other ye;u-s a~icl,I think, ;IS ;~c.ctlratc;IS collld be obtainetl for a natural pol~ulation. Su~~vlvorts~l~r~7r~~~c01; KESII)I TABLE 40 NUMBERS OF ~ Marc11 April May June July At~gt~st ---.-. .- ~ ~ -.------1960 Females I - - - 12 11 4 Fr~~~ales11 ------ Males 1 - - - 10 10 7 M;~les 11 - - .- - - - 1962 Fc.l11;11cs 1 20 20 12 11 ti 3 Yc~~ralcsI1 I X I !I 18 18 I I X Males I 1 7 1 X 15 l 7 12 8 M;~lcs TI 15 15 14 I4 8 5 llIf5" I;~~III;I~(.sI (i 5 8 (i - - I:clr~;~lc.sTI 12 12 17 1 $1 - - Males I I I I I 12 12 - - Males 11 5 5 8 9 ------* Atl~~ltskilled at end of June. very ro~~ghlythe ages at the time of the deposition of lst, Zntl, and 3rd clutches. The death rate for fcn~alesis lower tlian that of males in altnost all age cl;~sscs.Mort;llity is high tluring tllc first few weeks of life, but fairly consl;tnt tliereal'ter (Fig. 17). Perllaps 15 per cent of the females survive to sexual niaturity, I~utlcss than 10 per cent of the lizards live past the age ol one year. 'Table 41 A'r OR NEARHATCIIINT. OVER A ~"IVE-YEAR~'ERIOI) ON TIVOSTUDY AREAS 'I'lrc figures in tlic table are Ixtsed on 482 males, 585 fcilrales; Ix = n~~niberalive :it bcginrring of each age interval; dx = nu~nl)crdying during the interval; qx = ~xrcent;~getlyir~g of those alive i~ttlic 1)eginning of the iliterval Age Females Males iutc.t-v;~l -- (weeks) tlx ClX I x tlx qx 'I'llc n~;~xi~nulnlorlgevity obscrvctl ;rInong h;rtchlings clul-i~igtllis stl~tly was 100 weeks for ;I single fcm;~leant1 97 weeks for one r~lale.Fewer tl1a11 1 per cent 01' the m;lles livctl 57 weeks; ol' fetn;~les,60 weeks. The average life expect;lncy at h;~tclli~lgis abo~~t18.5 weeks. Althougl~the tlata 111;iy not be exact, 1 (lo not hesitate to st21te tllat the suggestio~~of Tinkle c,t (11. (1962) that the pol)ul;rtions might sllow an cssell- tially ;UIIILI;I~turnover 11;~sbeen ve~.ifietl. To say that the popul;~tionturllovcr is esse~ltiallyco~lll~lete every year is not to deny that some ;rni~r~alsmay live two or more years. If we had a popul;~tionof illfirlice six, I am certain that ;II~oc.casiona1 :unim;~l 3 or more years of age woulcl Ile fountl. /Is a mattel of Iact I have recortled one feniale 'X I000 -0 900 - 800 - 700- 1 I 'r I 600 - 'P 500 - 400 - 300 - 200 - I00 - 0 Ill~lll~tlrrr11~1 3 9 15 21 27 33 39 45 5 1 WEEKS SINCE HATCHING 1:1c. 17. S~~r\i!or\i~il)cur\(, SOY 1 I11 ~L1111~61111(111(111121lcs (solid li~ic):k~i(l f(,~t~ali,s (I)rokct~ li~ic.)I);~setl on clala it1 Taljlc ,11. See lcst for ~~SCLISS~OI~. first ~n:u.ketl ;IS ;r 50-111111 ;1tl11lt in iLI;ty, l!)(i3, that was last rccortled ill R/I;trch, 1'365, at ;lrl age oS ;tt least tliree years. However interesting tllesc may be ;IS ~-eco~.tlsol' longevity they are 01' little importance in tllc tlynamics ol' rlle pol~11;1tio11.The S:tct 1.ern;rins that tl~cmajority ol young are protlucetl by li/;~rclstllat ;11.c tllc~nselvesyoung ol tile 111-evious year ;~ntlthat will be gone 11o1n tlie ~)ol)ul,tt~on,lo1 the most 11'11 t, I)) the time ol the next breeding 5(~:I',oll. Tl~csurvivorsliil) data do not show ;I tonsistent relationshil~with ~iat;tlity. In other worcls, s~~rvivo~.shil~is not ;tlw;tys highest when natality is lowest. Other tlrings t11;tn the ~rumberof competing individ~~;tls11l;ry :I ~n;tjor~);wt in s~~~.vivorsliip. I~Vlrctl~c~~the s~u.vivorsliip tl;tt;t p~.esenretlwill ba1;rnc.c wit11 tl~ccstinlatetl ~,el)ro(luc.tivc.lx)tarti;~l ~.en~ai~~s to be clisc.~~ssed. If c;tcli fcnlale l;litl 3 c.111tcllcs ;tve~.;rgil~g(1 eggs e;t(.Ii, t11e11 12 young per fem;rle wo~~ltlbe l)~.otl~~c.etl,of wllicli (iwor~ltl he I'cm;tles. St~~.\iiv;~lof 15 per c'ellt of these to maturity woultl 1.esu1t in O.!) ;t(lult I'eni;tles. 'This is all tli;tt is reclttiretl to niaint;rin ;I constant ~)ol)~~l;itio~~level I)ec;tuse t1ie1.e is only !)O per cent 1111-nover of tllc ;ttlttlt I'em;tles. 1lowcve1-,1;igul.c 17 ;111(1 [lie tl;tt;t in lnble 40 inclic.;~tet11;tt of the 15 ])el. c.c~~ts~rrvivin~ to ni;tttt~.ity,only two-thirds will livc t111-ougll the ~.cl)ro(l~tc.tivese;tsoll. 'l'licse c.o~lsitler;~tio~~s,;tgain, give c.atrse for doub~tIi;tt nly csti1i1;ttes of ~.~~)~.otItic.ti\~epotenti;11 al-e correct. I-Iowcvei., if the tl;~t;tof 'I';tblc 37 on ;ic.tu;tl ~r;~t;~lity;tre ~~sccl,c;~c.ll i.esitler~t I'eni;tlc 1)roducetl 15 yo1111g.'1'11is IIIIII~~)~I.is st~fIic.ient to 11ii1i11t;ti11;I ~OIIS~;III~pop~11;ttion si7e il' every fem;lle st~rvivi~lgto ~n;tttt~-itylives long. enough to 111.otlt1cc ;tt 1c;tst 13 or 14 oll's1)riny:. '1'0 ac.c.ornl>lisl~this sonlc, if not most, of tllc frnlnles niust 1)1.ocl~1c.cnlo1.e t11;111 three c.lt~tclies. I)IS(:IISSION01.. I,ITI~KA-IIIRI.: ON S~IRVIVORSI~III~ IN LIZARI~S.-D;I~;~ 011 SIII.V~- vorshil~in 1iz;trtl ~~op~tl;~tions;tl-e r;u-e. Hail. (1960), b;tsing his estini;~teson tlleorctic;~l n;tt;tlity r;ttllc~.t11;tn on the sm;tll i~l~ml~crol' juveniles ;tc.tn;tlly m;t~.kcd,cstim;ttctl t11;tt 6-20 II~I.cent of tlle l~;ttclllin~ss~~~-\/ivetl to ni;ttu~.ity :III~t1i;rt ;tl)ol~t20 1)cr cent of the ;~clultssul-vivctl to ;I seconcl breetli~~g sc;tso~~.Fi1c.h (195(iD) rel)ortctl mt1c11 higher sirrvivo~-sliil)in Crotnplrytrr.~ c,ollnl.is, in w11ic.h neitrly 40 per cent ol the young s~ir\~ivcto sexu;~lnl;rtu~.ity, ;rntl ;tbo~~tone-ll;tlf of these live to ;I secor~tlse;tson. Crens11;tw (1955) repol-rctl, ;tlnong ;I sclectetl gro~111of I~;ttcllli~~gs,th;tt 50 per cent loss occurl-etl tl~~ring the li~.st(i weeks of life ;tntl (i8 per c.c~ltin the first 2 ~nontl~s,st~ggcsting ;I ~ilo~.t;tlityschetlule siniil;~rto tl~;rtwhicl~ 1 11;tve fountl in tttas. Si~nil;~~.ly, Hil.tl1 (l!)(j:l) repol-tetl that less th;rn 10 per cent of the li/a~,tls~tr.sili.sc.r~.r 7~il((l~/l.S;tncl Atnc,iucr q~rtrtl~.ilitrc~c~tcrlivc for one yc;tr ;tntl only 2 per ccn t ol' IIcr.silir.r~.ssltrvivc two yc;us. Sexton cl (11. (1 963) and Stol-1. (1 96 5) suggest cssenti;tlly ;tnnu;rl turnovel. in Anolis linr ifrons ant1 /I tt7plr iDo111r1rsi.solcpi.s, resl)ectively, bt~tthese I.el,ol,ts ;Ire basetl pi-irnarily on ;I consitlc~- tion on of si/e grou1)sprcsent ;~ttlilf'ci-ent times of' the ye;tr r;~therthan on rec;ll)trlrc of ~ri;t~.ketl;~ni~llals oS known age. Finally, Fitcli (1958) reported 50 per cell1 rccluc,tio~~c.;rclr ye;rr in atlult ~)op~tlatio~~sof (:rrotlitloplrorrr.s ,sc..xlirr~trtrl.r. Altllougll only 21 srn;~tteringof data are available, these ir~clicatewidely tlif- l'e~.enttlemographies in different sl>ecies pol)ulations. I~\/IMI(:I I cxc.l~;il~geI)ctwcc~~ clc~r~cs ;il~cl wit11i11 t11e111. 1;o1. tl~is1)111.1>ose, I t~.ieclto ol)t;iit~ ;I III;IX~IIIUI~~esti~niilc of movelnerits illto the ~,op~~l;itionby the following pro( cs. 111 tllc ye;il.s l!)ti lL(i.1, ;il~l~ost;111 youl~g111;is were 111;rrked cluri~lg the stllllnlcl. i111cl c;irly 1;iIl. If it is ;~ssi~~~~ctl11i;it yo~~llg li/;rrtls 1n;lrkecl ;~fter ['it11 we1.c. i~litilig~.;il~ls;111cl lIlill ;I(I~I~IStil;irke(l 011~si([ctlle ;ire;i ;III(~ I;I~cI. I)eco~liil~gatr~tly ;u.e;i 1.esitlents were ;ilso inlriligr;~~~ts, then I can cletermine what ~)l.ol~o~.tior~of tl~c I)~.ectling ])opt~l;~tion ~IOIII l!)(i2-(i5 was con~l)osetl of ill~nligl.;int 1i~;u.tls.'l'hc figures obt;~i~~etlI 11iixi1111bec;i~~s~: 1 ;111i (.et.t;~inrll;lt Iriarly young li~;~~,tls11i;irketl in l';~ll;rncl winter were 131-ocluc~ecl 011 tile ;II.~;I.No co~lll)i~~.;rl)lcligt11.c~ (.;III I)e give11 for e~i~igr;~tiol~,IIIIL I ;ISSIIIII~ tile two processes ;~rcI);il;~ncetl ('1':iblc 42). l'liese t1;lc;i intlic.;~te;I 111~1(.11I~igl~er tlegrcc 01' i111111igt.ation 111;ln those I)~~evio~~slyco~lsicleretl. In some yc;lrs, no re tl1;111 or~c-h;~lf01' the ])I-eeclirlg ;lc[,~]ts1ycr.e irn~l~igl.;~~~ts.11 is clific.1111 to (II.;Iw ;illy c.onc.l~isio~~sc.o~icernin~ col.l~cl;l~io~isI):.twecn tllc ])~.ol)ot.tioi~ol' i~i~~lligl.;it~ts;11110r1g t11c ;~tlults;111(1 I 1rE .INI) r)t AI~GRAPHY01 UTA 133 the tlel~sity.For es;~lnl)le,tlic percent;lgc of imlnig~.;untsamong the 1-esiclcnts 011 ;II-~;I I in 1962 was ;~l~ourtl~c sarnc ;IS ill I!)(i3 mrl1e11 the density was about hall tli;~tof the previous ye;il.. If imnligl-ation is, i~ltleetl,as high ;IS a11 ;iver;Ige ol 40 per cent, then cssenti;ll ~);~nlnixiais intlicatetl. Krio1)S (1963) t.on~p;~retltllc vlu-i;~tionin liz:~l.tls Tro~n tllr l ,111ly 17, I!)(il: ,\tl111t J ~narkctl 25 nllrl 011 ,111ly14, l!)(iO; c;~l)tllrcd564 feet 11o1.tl1ol original loc;~tion. ,l111y 1.1, l!)(i2. :\tl111t 8 c.apturetl 500-!)OO fcct ~~o~.tl~c;tstol' whcrc it was m;crkctl as 11;1tchlingon J11ly 13, I!)(; I. R/1;11.c11IS, l!)(i,I. /\tll~lt Q ca~~gllt300 Seet so~rtllof loc- tion on wllcrc she W:IS m;~rkctlas 3 1 -1nlr1 jl~\,e~rilcon :\II~IISL 15, 1963. ,1111le111, I!)(i.l. 1\tl111t d c,~l~tr~~etlSO0 fcet south ol loc,~tiol~~rl~e~c il Ii,~d I)ecl~sccn 1,rst in Scl)tcmbcl, 1!)(i:l. ,J11ly25, l!)(i.l. i\tlult 9 c;~ugllt;rl)ol~t !)OO fcet c;lst 01' 1oc;ltion MJII~I-cshe w;rs I;~stsee11 in Scl>ternber, 19(i:3. bIarc.11 20, 1!)(i5. Sulx~tlultd fount1 (iOO fcet sot~tl~ol loc.:~tio~l~~lle1.e rrl;~rketl as a 25-~nmj~~~~eliilc 011 O( tol)er 3, l!)(i4. 01 solrlc 3500 li/artls mal.ketl, tlicsc ;11.c thc o111y ~.cco~-tlsof \'cry long e~nig~.;~tio~~s.rl'l~c~.eal-c too I'cw I-ecol-tlsto be cci-t:~i~~wl~ieh scx is more of'tell involvetl, ;~twll:~~ tilne of the yc;~~-enligratiolis oc.c111.,01- in what di~-cc.tio~~. The whole list ol' such rccortls was incl~~tlcdhecause they (lo intlic.;~tetint some liz;~l-tls no\-c scve1.:11Ilt~ntl~.etl Sect orlt of tllc ;u-ca. 'l'hc otltls ol l~ccovcr- i~igil~clivitlt~;~ls 111;1ki1ig SIICII 11iovc111e1its;II.~ lour elsen whc11 1;11.gesa1n1)lcs ;Ire taken outside the area. Finally, the ~n:~~-gii~sol tl~e study area were Ireqllently investigated to dist;lnces ol 309 feet beyoncl the area bo~lntlaries.Kecortls were not always (Ii.win, 196.5) followctl closely tl11-cc 1);1il-s of IIC~IStor scvcr:~lweeks. Maliy cortrtsliil)~were obscrvctl, sornc or~tsitletlic 1)resitmecl pair boritls, hut all of thc col)ttlatio~~swere bctween the l~rctlictetlInates. As poititccl 0111 earlier tl~c.nlollogalny is ~)resulnablyfacr~lt;~tive ;mtl is l~rodl~cctlby the nggressi\lc- ness of both scsrs tow;~~.tlintlivirIrt;~ls of the saiue scx. 71 7 he cluestion of interest is whether tllcre is any atlv;uit:~geto monogamy, ])el- se. Tinkle (19(i50) sllggested that nlonogainy niiglit incre:~se the clegree of or~tcrossingin a rel;rtively setlentary li~artl.Fl'l~e ;tssulnl)tion that iiiust be nlatlc is tli;~tc;~ch iti;~le Iiiates witli 1)rlt one female (luring his lifetime. This wo~~ltlprovitle greater outcrossing than il' a sirlglc m;lle ~r~ate(lwith several lem:rlcs. I-Iowcver, iT the single malc came Srom :tnother ;lt.e;l, the amorint oS outcl-ossi~~gmight be greater that1 in the monog;unoas systeni if 111ost of tlic monogiranlous pairs were sibs or close relatives. I cloll't think ~nysrlgges- tion of the f~~nctio~lof nlonogamy sl~ortlclbe take11 too seriously. If tllosc li~ardsthat arc monogatnorls protlr~cemorc sulviving offspring th;~iitllosc that are polygamous, ant1 il the bontls tl~;~treslilt in 1ilonog:lrnorts pail-ing are gcnetic.:illy I~asetl,then :I selective atlv;~tlt;~geworlltl ;iccruc to 'iiio~~oga~iious1i~;trtIs. 111 the allsent-e of suc-h cvidcnc-e I prefer to think 11i;it nlollog;imy results siinply froni intrascx11;11;~nt;~gonisrn ;~ntl the al)setice of soc.i;rl hier:~rcliies in the l~ol~ulation.Tlie iiggrcssive beli;~vio~-is clearly ;tclv:u~t;~geous:u~tl :~lmost certainly inn:~tc, so I am sticking c.loscr to the f;~c.tsby rclegaling monoganiy to a sccoticl;~ryel1ec.t r;~thc~.than to :I priinary func.tion. 11 m;~yI): somewhat ;ull~big~~ousto xl)e:tk of the cficctivc I~rcetlingsize of ;I natural pol~ulirtion,but tlic ratio I~etwccntllc ellcctivc six ant1 the total nr~n~bet-ol potential breetlers may be meaningful. The efl'ective si~e n~igl~tI)c \,isrl;ili~ctl;IS the 1111n1bcrof lizartls tti;~tat-c PI-otlucing ofl'spring t11;it srt~.\~ivcto ni;~t~~l.ity.I-Iowcvel-, bec:rrlsc sonlc tloubtlcss protlnce inore ~II;III otliet.~,in ;III cstitn:~teof the cllcc:tivc six one must consitlei. the vari:unce in ~xoilr~c~tionof srirviving oll'sl~ring.This was tlorie by Tinkle (19650) who I'or~licltI1a1 the elfective six was about the s;tme 21s the ;ictu;rl nliinber of 1);iil.s ol' resitlent ;rtlr~lts,intlicating tIi;tl c:~clipair was ~)rod~~c.ingaborrt thc s;tnlc nr~lnberof sr~l-vi\,ingollsl~ring. 111 yeai-s in which 11;ttality was hig11 ;tlitl winter ~nort;rlity low, conipetition :inti selection among the young were p~-es~um;~l)lyincl-e:tsetl. At certain times like these the young ol some females M1ei.e ;IL an atlv;rnt;ige ;rntl sr~rvivetlin morc tllan random ntrmbei-s, resulting ill ;rn ellcc.ti\,c 111.cctlingsix that wits lower th;rn 11slla1. 111 c.ol~c-lr~siol~,it ;lpl)cars lh:rl the utas arc gencr;~llymonogamolls ant1 ~-i~nclolrlin their ~~rotluctionof surviving offspring. If the figurcs on maxi- mum emigration a-c brought into account, any tendency toward inbreeding that resulls Irom the low tlegrec of inovement :uid the formation of inter-sill 1r1;rtirig ~>;tit.sis coiiil~crisrtc~lby tlisl~el-salinto the st11cly ;Ireas f1-om adjacent ~~olx~latioris.Finally, the rcatlirless wit11 wllich ;in ;tdr~ltmale will court l'e~nalesother than its ~tsu;il~n;rtc, coripletl with the continual movements ol' 1n;rlcs arountl their lloine range pcril)he~-y,insnl-es that every feinale will be rertili~cclslrot~ltl her usu;rl inate be preyetl ul,o~~. I7 here is so little inlorm;~tionin the 1itcr;rttrrc on hreeding structure ol 1iz;lrtl l~ol~~~lationsthat I hesitate to makc generi~li/ations.mow eve^-, one secnls :rppal.ent ant1 tIi;rt is t1i;rt 1e1u;rles ;111ilost always ot~tnumbei-males ;r~l~ongatlult li/artls. 71'liis w;rs tlcmonstratctl ill tl~isstutly ;IS well ;IS by Blair (1!)60), H;t~.~-is(l9tj4), ;rntI Hirtll (l!Iti.Y). It nl;ry illso be trne that ;I f;~c~~lt:~ti\rctype of Inoilog;rmy n~irybe inorc colninon th:~ii is generally tliot~ght.1,orenz (I!)titi) 1-ccortls ;In observation on the South 1Su1.ol)eaiiC;recn Li~artl(p~.es~~m;rbly L,N(-('T~(I ~);?-;dis) in his expel-i- ~ncntalc1ic1osu1.e~. Fl'lle inirlcs irntl fem;rlcs of Lcrc.c,rlcl tlefentl their territories only ;)gainst otlier 1iz;ri-tls of the s;rme sex. In;rsnl~~ch21s the tci-ritory sites are lirnitctl, he fountl t11;lt a p;rii- of tlorni1i;rnt males ;rntl Ic~n;rlcscame to be inatlvel-tently ;rssoci;rtetl ant1 col~nl;ltetl rnt~cli more 1'1-eclt~entlywith one ;111ot1lcr tl1;111wit11 cIi:~~i(.e1);Irtnel.s nlet at the territory 1)0~111(1:1rics.1-IIC rr~novalof one nle111be1-ol' tllc ])air rcsultetl in fighting irtnong the st~l)o~.tli- nates with tlie 1.es1ilt t1i;rt the most ;~ggrcssiveof tllosc soon lilletl thc virc:rncy. 1-1.'IIIIS . .' (I!)ti4) tlocumentetl 5 inst;rnces in which 1'em;rle Agcrj17cr crgcrlrlcr rc- ~ni~i~letlwith their tlo~niii:rnt irialcs tIi~.olrgho~ttthe bi-ecding season, pro- tl1rcing thl-ee or four clutcl~es01' cggs each. Tlicl-e :II-e often sever;rl feln:rles :rssoci;~cctl with ;I tlomin;lnt 1n:tlc Agcl/tr(r, I~utirll arc submissive to the tloriiinant I'cmale. In no instanc-e w;rs ;I tlomi1i:rnt Fem;rlc obsel-\red to le;~\le;I tlominant ~n;rlc,wlle~.e;rs tlese~.tions by subortlin;rtes w~crccommon. 7'11at this f;rcult;~ti\~c1nonog;uny tlitl not last I~eyontlone I)~.cetlingscirsoii was owing to ~.eshulflingof tlie l)ol,lrl;~tio~~tlul-iiig the non-111-ectling se;rson, so that. ;I tlonlinirnt ~n:rlc was with a tlill'erent Inirte the next bl-ceding se;rson. In such c;tses ;IS tllese tlic :~(lvant;rgcof 1nonog;rrny seenls c1e;rrly one ol scxtrnl selection. i\t the s;inle time the social hierai-cl~yallows iri;~inte~lance of ;I l~igl~tlensity, ;rntl ~,~.cs~~~iiitl)lyof ;I higll I-el~i.otluc.tivesrrcccss, ;nitl ;rt the a;tinc. t i~ncminimi/cs conllic t. 'I'hc ~.el;rtio~lof si/c to ;lge in rile 11ol111l;rtiorlsof the stlrtly ;rl.e;ls may be scc~iin '1':rl)lc -1-1 l'oi- those li~;rl-tls~n;r~-kctl at tl~c;~l~l~ro>ci~ii:rtc ti~ne of 11;rtching. Only data lor tile stlniniel- ;11-e shown, nntl it is cle;l~-tliirt tllc ~)olx~lationsat this season are co~nl~osetl;11inost entirely of liz;~rtlsth;lt al-e either about one year oltl or arc young ol the year. A few second-year ;~dults ;ire also 111-ese11t. I IFE ANI) T)E.ILIOGRAPHY01. ~JTA 137 MI..ANAGES OF LIIARDSOF \'ARIOUS SNOUT-\-FNTLENGTHS Data Imsed on lizal.ds tnarkcd at hatching. Data rcstrictcd to the pel-iod Junc-August; all years ailtl areas con~bitlccl . - -- -- 111111 I\' x age (days) N x agc ?I'hc 1)imonthly clistribution oS size gi-oups is shown in Figilrcs 18 ant1 19 Tor males and females, respectively. The shift in size groups reflects the rapid rate of growth; young of tlle year ant1 one-year-old age classes overlap by fall. 111 these figures there was no way of showing the 1)recise ages of the O/o N 8 10 mos m 2 0 20 300 4 20 M 18 4 5 [:I(.. 18. ~~~~I~()x~~II~IIcage SIIIICIII~~ of III:I~(,~in :I 'I'cxab IIL;I l)o1)111;1tin11nvr1- :I ])e~.io(l of several years. Abscissa shows s~lor~t-vc.111Ic~rgtl~ ill 111il1i111ctc1-s.Ordinate shows 111ontlrs of year. Tile al)ljroxiln;~lei1gc.s of tlrc sisr classes XI-ci~rtlicalrtl on llrv I~istograln.7.1ie per- cc~rt;cgcs;rl)nvc soll~rI~istngl-a~ns ;II-c ~)~-oljo~-tio~~rof tl~i~-tl-sc;~so~~ ;~cl~tlls. Srr t(.ur for fr~rrl~~r cx~~l;~~~;ilio~i. animals composing the si~eclasses, but ;~l.bitr;u.y ages cat1 be ;rssignctl fairly acct~rately21s lollows: most hatching occurs ;~bol~tJlrly I, so 1i~;rrtlsin thc Augt~st-Sel)remI>c~.xe;rson (8-9 ill the fig(11.e~)wot~ltl be either I! 01. 1.1 rnontl~~ 11~.10. Approxi~l~ateage structure of fctl~alcs.Infortnation salnc as irr Figure 18. old tlcl)cnding on whether they were yorlng of the year 01- :r(l~rlts.Thcreforc, this ligl~rcalso shows in ;I soniewll;~tinlprccise wily the degree oU ovel.l;~l~of the tlifferellt age classes. Note that at no time of the year ;rt whicll this ~)opul;~tionmight be sampled woultl it be possible to separate the age classes on thc basis of si~e.In tlie summer, the young of the year may be separated fl-om the adults (5ee Table 44), I~rltthe olle-ye,~~,~nd t~~o yea crgml,rsses are inseparable by size criteria. Table 45 shows rather precisely the age coml~ositioliof the 'l'exas polmlation at each of four seasons. This table shows in a striking way that the pop111atio11of lizards is coml~osetlprimarily ol young of the year (over *\(.a DISTRIRUTIONIN TH1' 'I'FSAS~OI'IJI.A~I'I~N~ OF ('(17 ~~011~~~111~2'(1110 .AT Iflll~ SFA~ONS Yc;l~-satltl arras co~l~hi~lcd.1\11 ligurrs arc pcrcentagcs -~- - -- - .- -~ ------~. --- - ~- I 1M;rlrs I I'rlllales ------Agc in N 724 117 1 :3 58 1 983 1!)O 20 I03 I);~ys ,]ut~c-t\ug.Sel~t.-Nov.1)cc.-1t>l1. M;~~-.-May,]l~r~r-i\c~g.S ,p~.-Nov. 1)cc.-Fcl~. ~,I;II..--~I;I!. -.- . ------. -. - --- .--- SO 70 12 - - 77 .I - - 60 15 13 - - I (i 12 - - 90 1 4 5 - - 1 44 - - 120 - 17 X - - 25 10 - 150 - 1 0 3 I - - I I 30 - 1x0 - I 3 I 5 - :i 10 :i 210 - - 15 4 - - 25 (i 2.10 - - S I(i - - 25 I!) 270 - - - 43 1 - - 4 1 300 1 - - 16 2 - - 10 330 1 - - I (i 2 - - I0 360 I - - - :i - - - :K)o 1 1 - - 2 -- - - 420 - - - - .2 2 - - 450 - - - - 1 1 - - 90 per cent of the pol~ulation).Some care must be exercised in i~iteqxeting this table. There is little c1o11l)t that the figures lor the srlmmcl- monlhs :iccul-;rtcly I-eflcct the PI-ol~ortionof animals of tlitFerent ages ill thc n;~tr~l-;rl pol~~lation.The small samples from llecernber to February c.oultl not possibly I-eflect the proportion ol' clilferent age groups in nature. Neverthe- less there is no mistaking the fact that the age stl-trctl~reis a simple one- LIFE ANI) DEMOGl TABLE 46 A(:L: I)IS.TKII~UTIONOY ADUI;~ I\NI\IAI.S I IANDI.EI) EACII YEAR ON TcvO AREASFOR \VFIICII TIIE AT.^,. OF THE ANIMALWAS KNOWN All figures except total lizards are percentages .- - . ~~ . Tola1 First year Secontl year Tllirtl year 1iz;lrtls adults LI~LIIIS adults .~ - - . p~- - 1963 Atca I '1 2 90 10 0 Area 11 (i2 8Il 11 0 1965 Area 1 55 93 7 0 Aleit I1 65 02 (i 2 Totills 581 9 3 7 .02 I)lsc:~rss~o~01:~1~11.: I,II~ERI~IIKE ON AGE STKIICTIJRI;IN LIZAKDS.-TI~~ age SI~IICLII~CITIIISL 11e ktiowri to ~~n(lerst;~n(lthc tlynamics of natural populations. 1711e rel~rocluctiverate ol' a ~~opulationis untlerstantlable only in terms of tllc age structure. ~ILICII no re Frequent than c:~refulanalysis ol' age structure it1 l~ol)i~l;ttionsIr;lvc been repor~sof long-livetl anim;lls (e.g., Fitch, 19560, ol :I 9-year-old 1Crlrnec.o.cfn.rt.zcifrr.~). /\ case in point is :I recent study by Tanner (1 965) in wliich lie statetl: "Our tlat:~on longevity in IJtn tlocs not agree with tliat recently pub- lishctl by Tinkle, McC;reg;u- [sic] ant1 Ihna (1962)." Actually, Tanner fount1 tllat (i of "over 100" utas ~nai-kedin 1960 were alive in 1962. Thus, some tltas li\,c at 1c;tst 3 years, but his tlata intlic;~tea turnover of about 75 per cent of the ;~dults,;I turnovei c.onsistenl with what I have foltntl in some Utcz pol>ulations (see section on comparative demography). Age structure will tloubtless tlifler in cliffel-ent species and even in the same species in tlifferent parts ol' its range if environmental contlitions are significantly clifl'erent. Kranle~.(1946) it1 his stuclies of L~crcrrta .sic.~rlcrsuggesteel that the age structures of acljac.e~ltisland ant1 m;~inla~ltlpopitlatioils of this species were tlitfe~,e~~t.011 the islantls the 1iz;rt-ds lived longer, h;ttl ;I lower repro- dllctivc ~.;rtc,;t~~cl ;rpproxinl;rtely twice as long :I gener;ttio~ltime as 1)ol)ul;r- tio~ls011 tl~c:~tljac.e~lt m;ti~ll;~ntl. Such co~lsicle~-atiollsarc importa~ltbec;i~lsc tl~eyatl'ect the I.;rtes at which ge~teticchanges (.a11 take 1jl;tc.e in tl~e1)optt- lations. rl'llcl.e ;IIY ;I~I~LIL10 stllclies in the 1iter;tture in wllic.11 solne useful tl;tt;i on age structu~.ellave been obt;~ined.In S(.~loporrrs~rrrtlirl(rtirs (Crenshaw, 1!)55), A~ro1i.s1irrrift~on.s (Sexton (,/ (I/.,IY(i3), ;~ntlA,trrci~)ci c/rrmtlrili~iec~tci ;untl 1~cr.sili.sc.rrs71itt(itirs (tlirth, I!)(i3) tl1e1.c is ;I si~ttplcage structl1l.e like that of liltr, cvitll esserlti;~lly;II~IILI:I~ ttlrllover of ;rtll~lts.In lit^ .stn~l.sD~rricrtict(T;II~- IICI., 1'3(i5), S(~,lopotir.ro1i-r)crt.cir.s (12lair, IWiO), it11tl S(.rloportr.s occ~irlrt1ttr1i.s (Fitc.11, 19/10) there is ;tl>out 75 per cent ;tnnt~altui-~lovcr among ;ttlults. 'This 1.ctluc.etl t111.1tovel.is not ;rlw:~ys ;tc.c.o~nl);tnietlI)y ;I I-eclucetl 1~eprotluc.tive I.;ite in;~sln~~c.h;IS th;~t 01' S. o1i-ocic.crr.s is I~ighcrthan ;tny other sl)ec.ies. In Err ttic,rc.s ohsolc~/rt.s(Fitch, 1!)55) ;t~~tlSc,cloporir.s guicr os1r.s (Stebbins ;t~rtl Kobi~lson,l!)l(i; Stebbins, 1!)48) tlle age stlxtc,tur.e is more nearly b;~l;tncctl 1)etwccll young ;rntl oltl ;tnirn;tls titan it1 the ~~rcceclingsl~ecics. In the filltnc,ce.s, over ;I 5-yc;11.~)cl.iotl ;~clt~lts co~nl~~~isetl 4.3 pel- cwlt of the ~)ol)ul;r- lion; sttl)aclults, 26 I)er c.ellt; yc;~rlings, 26 pet' cent; ;tntl h;ttc.llli~lgsot~ly 5 pel' cent. 111 the .Y(~clo~orrr.s,I(i pel' cent of tl~e;ttlults rn;il-ketl in 1<)4!2wet.e t.cc.ortletl ill 1945 when tl~eystill co~nl)risetlone-thil-tl of tltc aclult 11op11l;t- ~io~t.Eight of 73 li/;~t.tlsin 1'347 were marketl ill 1942. Even 011 a conser\rative b;tsis, assunli~~gth;lt ;ill ol' the 1942 ;~nim;ilsIl;~d been yc:trlings, over 15 1)cr ccnl livecl to he foul. years ol' age ant1 about 11;tlf that m;tny livctl to be six. Never ill this higll-;iltittttlc 11o1)~tl;ttiontlitl yoil~tganimals out~ll~tllber;rclults cven if the ye;trling ;tni~n;~lswere c.onsitlel.etl yo~r~~gol the ye;u.. Long-lile expcct;tncy occurs tllrol~ghtlecrc:tsecl ~llortalityof juveniles ;~ntladults. This tlecrease might be accomplished by p;irental care or lnigltt occur autom;ttically in areas where interspecific competition was 1-etlucetl. The evolution ol' a 1;trge botly si~eor spinosity might retluce pred;tto~.pres- sure ant1 ;rllow grc;ttei- longevity of ;~tlults.An ~~nclerstanclingof tllc f;tctors i~ivolveclin producing the obvious tlin'ere~lces in age struc.t~u-eof li/artl p01>~11:1tionswo~~ltl be of gl.e;lt ir~terest. LIFE AND DliMOGKAI'HY 01: UTA 143 The iact that utas nlove sho~t distances and that their normal move- ments ;ire not easily interrupted by close observation made censusing ol the anim;tls by 1,incoln Index methotl a lairly accurate proceclure. Also, in the process ol' weiglling li/;rrtls, relxtinting the young, ;lntl performing other operations, we 11;rtl occ;rsio~ito atteinpt to C;IIILUI-~every lizard on the areas over ;I sllort pc~.iotl,usu;tlly 2-5 d;tys. 'l'lle total number removetl on s~1c.11 occ;tsions was consistently ~vitl~i~~10 per cent of the Lincoln Intlex estimates. During the slllnlliei. ;tntl early fall, when the areas were worketl inten- sively, we knew rittlier p~.eciscly how many animals were present at ;my 11;1rtict1lar ti111c. 'l'lle only problcin was to tlecitle which of the lizartls call- tltrcd were 1.e;tlly wing tllc st~~tly;tre;t to ;I signific;~ntextent ant1 wIli(:ll were t~~;~nsientsor ~n;~~.gin;~l intlivitlt~;rls. Therefore, 1 clesign:ttetl its resiclents tliose 1iz;trtls that were c;tpt~~retlat lc;tst t111.c~timcs witllin tlie st~~tlyare;(; I have b;lsetl tleiisity figtt~.csof ;tclt~l.tson tl~cntt~i~bcr of resitlent li~itrtls. \\lc llave :~l)lxo;t(~hctl100 ])el' (,en[ effic.ier1c.y in rcgisteriilg the juven;tl II~;ISlx'otl~~c,ecl e;~c,ll yeitr. I%ec;111seof the 1;trge numbers it was rarely possible to I)e c.ertai11Ilow nl;tny were present ;I( ;I sl~ccificcltime or wllich were resi- clc~itsof tlic area. 1 II;IV~,tllerel'ore, ~,clietl;tl~nost entirely on Li~icol~lIlldex esti~n;~tionof jt~ve~lilctlc~~sity. I h;tvc ~,clicclon it ;tlso Sol- csti~n;tting1111111- I~crsol' ;ttlt~lts;tt se;isolls o~llel-tli;tn strltnilel. :tntl e;trly f;tll, for we selclo~n h;~vesr~llic.icnt c.;~l)tt~rcs (exc.cp~ tlt~~.ing tl~e sl)~,ing ol some ye;trs) to tlctermine which liz;t~.tlswere 1.esitlents. (;encr;~lly I col~ltlztssulne tli;~tan aclult tll;~t wits ;I ~.esitle~itin slllnlliel. ;tntl s111.i11gw;ts also :I 1.esitlent in fall ant1 W~IILCI-. I 11;tvo prcviot~sly~)roscntctl so~~ic tlata on tlcnsity ant1 biomass 01' utzts (Tinklc, I!)(i7). I I~OL\I Ii;t\~eInore tl;rt;t, I)eltc~.rcfi~ietl, whic.11 ni;tkc possil)lc I~ettcrcstini;ttes th;tn 111ose pl'esenletl 1)reviously. I h;lve tleter~ni~letlmol-c l)~'ecisclythe nu~nberof 1.esitlc11t;tclults present ;it e:tc.h se;rson (Table 40, s~~r- vivoi-sliil~section). l';rl,le 47 su~nni;t~.izesthe density estim;~tes~natle on tlie two stt~tly;~~.cas over ;I pe~.iotlof sevel-it1 years. Density seltloln varietl by inore th;un ;I I';tctor 01' two on ;t~iyone are;^ in ;my yeat-. 'I'he fig111.e~show clea~.ly t11;tt (lensicy w;ts f:tirly (.onstant from I\/I;trch througli JIIII~, INIL tleclinctl ;rbrul~tlyiri August ;tftc~.;I less l)recipitot~stlrol' in July. The clcnsity on the two st~~clyareas w;ts t~s~t;~llyal~out the stme in e;~cllyear, IIII~al-e;t 11 w;ts t~suallyc.ar~-ying more li/;~rtlsthan al.c;t 1. 'I'lic figures ~)resentetlhere 11;tsetl only ul>on known 1-esitlc~its;Ire so~uc- what at variance with those presentetl by Tinkle (19(i7) whicll indic;ltetl a mean tle~~sityol' I!) atlt~ltspci' acre 1'1-om kI;trcli to Sel)ten~be~-. lknsity on the sttrtly ai-e;ts increases abrup~lyin late ,June or c;~rly[uly ;IS rcc~~ttit~i~cr~tof h;~tchlings I)egins. 11~1-ingthe summer ~rto~ltllsI Iiave ;tv:til;~bleIiltnlel.olts inclcx cst i~nntesol' ju~~cnilesthat :Ire quitc accurate ant1 TABLE 47 ~)I * Aclul~\killed at clrd of Junr. some, less ;iccurate, for tl~cI;i11 months (T;tl,le '$8). Tlle figllres for the two st~lilyareas ant1 for tlift'er.ent years arc si~llilarant1 the cstinlates of j~ivcnile tlcnsity never v;lrietl I)y more tha~i;I fiictor 01, two. l%ioin;~sswits c.;llctilatetI ;iI'ter. sinll~lilyingasstunl)tions were r~lacle,vil., t11;tt the average tlensity 01' juveniles i11lcl i1(111lt~is illtlicitti~eof long-tern1 trentls, that eacli ;inirn;~l'sweight in ;I particu1;tr month is near the pop~rla- tiorr nicarl lor that ~nonth,;111d for its size cl;~ss,and that the sex ratio was practically 50:50. Hioni:tss may then be c;tlculatecl ;is the mean tlerisity mul- tiplietl by the meiin weight 01' the 1iz;utls obt;iinetl fro111 l'ables 13 ;ultl 1.1. Tlle figures a1.e cert:tinly not exact, but they are accurate enougll to indicate tlie trentls (Table 49). 7'11e cr.entls in I,iom;~ss ;Ire ;is reportetl by Tinkle (l!)(i'i), b~itthc figures ;ire tlillerent. The ;ivcr;tge bio1rl;tss is about 84 grams per acre, some- wh;~tless th;tn tliat c.;ilculatetl previously. Altho~iglltl1er.e are negligible n~urnbersof juveniles iri the sp1.ing ant1 11egligil)le rit~rnbe~.sof oltl ;~tlultsin the fall arid winter, there itre enor~ghro briq the 111ea11 figlire to ;t11011t 90 grarns per acre. I%iomiiss is highest in the early fa11 when the young of the ye;u :ire aplxo;wlli~lgadult sire. Dur.ing the winter ;I low ol abo~~t60 grams is rc;tcllecl. TAR1.E 48 I)I:NSI I'Y 01: ~U\.l~.NIl.l~SON TWOS'IUDY ARF.ASOVFR i\ '~~-IREI-YFARPERIOI) 71'l~eligllres Lire ~~rc;uis~>cr acre of scvei.al cstin~;ltesor tlirect counts ~~~ntl(,over sl~ort~~criotls of ti111c(III;IX~III~IIII, 3 days) -- ~-~ ~ - -- - Year Area J LII~ JLI~!. August S:.l)tc~~ibcr October ------I <)(i1 I 28 85 (i(i 72 51 I I - XI 75 72 54 x ;Itlull x adult tlcl~sity weigl~t M:~rcl~ I -I 4.30 A1)ril 1.1 .I .:m May I '1 4.30 JLIII~ 15 :<.so JU~Y I0 :I.sC) :\llgllsl (i 3.81) sr1)tcllll)rl. -- - octol)c,r -- - I .i kc tlel~sity,the 1)iom;iss tluling the year v;u-ietl by ;I factoi- of about two. \I\/ \I\/ i tll tl~etl;t~a 11ow i~v;~il;~blewe t.ot11tl 1jrob;ibly escilr1;ice tl~esecoiid;~~.y p.otl~~c.ti\jity01' this species. tIo~ve\ler,knowletlge of n~etaljolicraces ol [Itas untlcl. n;~t~l~.;ilcontli~iot~s is not ;~vailal)le,but the liiet;~bolicratcs are 1x.e- srllnal~lylow ;IS arc (lie eneqy tlernantls for activity. I leave it lor future herpetologists to measure the energy btrtlgec ol' the utas, but 1 thirik such ;I sc~~tlywill show tl1;it thcy ;we of ininor iniljortance ir~energy flow (I). R. ,Johnson, IY(i(i). It 11as alreacly been notetl that tlie stomachs of utas, ~jossibly fillet1 twice ;I clay, contitin about 0.1 grarrl ol foot1 on [lie average, niaking a total of 3-5 grams ol' i~isectsconsumetl daily IIer ;me in a l~op~~lationof ;tvel.;tge clensity. I /llll(,~~1 IlX. 1 :I ~1111r'li2 '1-51 LIIIC '(2 3-1 June '63 :{ 5 Jlllll! '(is 29 30 1 llll(,'ti2 I0 111ly 'GI 18-20 1 uly '(Z 25 ,JIIIY'61 31 J~tly-2.\11g. '(i2 !I I I i\~~g.'(72 I0 ;\11g. '(i2 I I .\11g. '(il I2 '\tlg. 'fil .Yl,/li, !\'lh 1. l(i.Sc,])l. '61 I7 S<,I)I. 'I; I 7 oct. ,(;I 8 O(l, '(;I I Nov. '(;I I2 No\,. '(;I l~lllll/1-,\111~~ I0 rV1:11., '(2 2!1 31 h'l~ll~,'(2 0 Apr. '63 ;Ivel.;lge weight ol' li5 g~.;uris1)~ ;I(.I'~ (71';~l)le SO), I);tsetl on s;~ml,lcstl1;11 ~ver-c probably ]lever colnl)letc, colrll)ares C;~\;or;~blywith tlic I~y~~otlictic;~l111c:rrr of 8.1 gr;lins pcr acre (Table zl!)). 7'11e ~.cg~~l;~tioilof' IILIII~~)~I.S ill rlre l~ol)~~l;~tio~isis ;III i~r~e~xs~i~rg pr-oI)lc~ir th;~tl)rob;~)Jly (.it11110( IIC SOIVC(I ~vitlro~~t~rl;~~~il~~~l;~tio~l 01' ficI(1 1)o1)111;1tio1is iri enc.losed are;ls, 1)11t solrie itleas call I)c p1.chetitetl. 'I'lie tcr-ritorial I)clr;~\zio~.oS tl~cli/;~r.cls tlot~l)rlcss I.escli(ts (lensit) to some extelrt, but the ;~\~;~il;~l,lccvitlc~~cc Ir.o~n tlris st~~clyi~~(lic.;~tcs tlr;~~ c 011- siclcr;~l)lec.o~it~-;~c.tio~~ 01' territory si~cn1;ty oc-(111. ;it Iligli tlensitics. '1'0 rlle extent tl~irtaggl-essivcrrcss is still ~~i;tint;~inctl;tt st~c.11 times, t1ie1.c ill I)r ;I limit to r hc c.o~iil,~.cssil,ilityol tc1.1.itory si~cso that sl);lcc M:OIII(I I)C(.OIIIC li~niti~~g.On the other 11;tntl ;~ggrcssive~~css;IL \my Iligll tlcnsitic.~Inay 11c sr~l)tl~~ctlj~~st as occ.ur-s in OIII. I:~l,or-;~to~-y~)ol)~~l;~tio~rs. 111 h11(.1r ;I c-;~scso( i;~l Irie~.;~~.c.lricswo111tl be cstablishetl whic-11 miglrt ;ICI lo l)r'c\.c~rt i~ic.~.c;~si~rg 1111rnl)c1.sI)y ~,es~~.ic.tingthe b~.eetling to ;tninlals tlo~r~ilr;~ntin the Iricr-:~~.clrics. /\s :t11~:1(ly~rote(l, ti;~t;~lity s~e~ils geric~.;~Ily i~rvc:~.s~ly ~~cl;~tc(l to l)ol)t11:1- 1io11tl(:nsily, s~lggcstingth;~r tlensity-clcl)c~~tlc~r~ 1;ictor.s ;II.~ ol)c~.;~ting,1,111 this is 11o1 ;I \,c~.yinlorm;~tive itlc;~.7'1ic1.e is little c\ritlcntc ol inc~.c;~sctl sr~rvi\iorshij)w1ie11 ii;~r;~lityis low 01. tlcc.~.c;~seds~rr\~i\~orsliil) when it is Irigli, in other. wo~.tls,tlr;~t s~~~.\.i\ro~.sl~il) is ;~lso tlensir y tlel)clltlent. I)IS(:IISSION 01; TIIP:L3~.r~;~<~\,r~~~<~; ON I)P:NSI.IYAND l~~o~~~ss.-Tl~c(I;II;I ;~\,;~il;~l)lc;II.C ~)r.esentetl in 'J';rl)lc 51. 'I'lresc clal;~;II.~ tlill~c.ull lo corn1,al.c l~ecausctlrc estii~i:~rcshave, in so~~rc:c;~scs, bccn I);tsctl on llrc total number ol li/,;ircls c.;rptur-etl witliol~tknowlctlge ol whic.li ;11iio1rg tlic~iiIV~I.C ~.csi(lc~its. 1,arge sl~ecics,;IS might I)c cxl)ec.tctl, 11avc low tlensitics. Fl'lic lriglrcst tlcnsitics 11;tvc I~cen~.ec.ortlctl ;inlong ~r.ol)ic;~lsl,ec.ies. It is ~~~rl'or(~ln;ltc*, tl~ough,tIi;~t so little tl;~t;~al-e ;~\iail;rl)leou I)io~ri;~ssI)cc.a~~sc tlris 11rig.11~;~llow more mealringlttl c.o~nl);~risonsof spec-ies 01' \/el-y tlill'cl.c~~tsi/cs. 11;11-1-is(I!)(;-I), for ex;lrul)lc, rel~ortetl;i tlcnsity ol' 36 per- ac.1.c in :Igtrtrrtr (cgcerrrn. Me ;11so ~)l.escntcclcl;~t;~ OII the Inc;tn wciglrt 01 a(lt11ts ~vhiclr(.;in I)r t~sctlto csr i~l~;~tc very rorlglrly a 1)iom:iss of about 2000 gr;ilns I)~I' ;tcr.c ill iJ,qrttr(e, avlric.l~ is many ti~ncsthe bioiii;~as01' (111 species 01' li/;~l-tlson my sttrtly nl.e;ts. .b\~lotller Lrc.tor making tle~rsicy co~np;ir-isons tlilfict~lt is the \sc~-~ic;~l tlimciision ill the home I-angcs oS so~ricliza~.tls. Thc ;ictiviry of Arrolis littti- fr-OTIS,l'or ex;~rnple,is c.eiiterctl in trees. 'I'hc higllesr tle~rsicy~.epo~-tetl Sol ally li/a~.tlis tlrar ol' 500 i~(l~~ltIl(~trci- tlfrc-1ylrr.s ((;;tglc, I!)'lfcr) in ;I 2~100-s(1u;i1.c-Ioot;~rc;i on 'l'i11i;ln Is1;111clill tlrc I'acilic. i\ssurning uniform dispersion over tile sur-rol~nclingarea, ;I cle~isityof bout 10,000 per acrc is indicated. 1)egenllal-(It (1966) 1)rovitletl some cl;tta I):rsetl on tlrc use ol a refilletl on one ;rvc.a; 44 juv. on 2nd ;IS~;L - (:rc~~sl~aw.(1!65) Scr,lo/~or-11.5firctcio!rr,! I -- S~cl)l)i~is(l!l4-I) 50 105 tlcl>:ntling Oil ;I I cs:l ;111tl sc;tse)ll scl. ft. al-c;~;vc~ y sq. fr. line tl.;tnsect 111ct1locl or cstiln;rting n1t111bc1-s.As iliteresting 21s the s~tttlyrilay be in s~~ggcslillgtli~lerences in relative abuntlanc.e, it is still ;I crlitle incans 01' obt;lit)ing density cstirn;~tcs. It I~ecameevitlent ear-ly in this st~~tlythat the limitetl rnovcments, e;tsc of capLrir.c, ;rntl ral~itlt~ll-novel. of utas matle them an itleal s~r11jec.t1'01- tlle strrdy of' the effects 01' I-;~tli:rtionon it natrct.al pol)~rl;rtion,sl)ccific:rlly ul)orl the clernograpllic p1.opel-tics. 7'he ~.;rcli;r~ionwas earl-ietl orrt in 1'362 using are21 I lor the exl)erime~ltancl ;trc;~I1 ;IS ;I control. 11 was 1-el)licatetl in 19(i-I with ;u.ea I I serving ;IS the experi~ne~~talarea. Prior to r;ttli;~tio~l,I;tbo~-;tto~.y strttlies were maelc to tlctern~i~~ethe tlos;igc ~.eclr~i~.etlSol- stc~.ili/atio~lant1 the lethal close so tllitt lllose :~tlminis- rc~.ctlin tl~elieltl cot~ltlI)? kept below tllcse levels. I);III~:ttltl 7'i11kle (I $)(is) clenlons~r.;~ tetl Ilistologic;~llyr II;IL ;In x-ray close ;IS higll ;IS 500 1. c.:tuseel only tel1lj)or;rl.y stel.ility in nl;tlcs will^ IIC;II.~~coml~lctc ~.cc.ovc~.yir~ 3(i tl;tys. 1)os;lges al~oveSO0 1. were e\~iclently~.ecl~~i~.etl lor I)ei.lnit- nent ste~.ilily.'l'he I-atli:ttiorl tlos;~gc ~.ccl~~irctlto kill 50 pel' cent of ;~II esl~cri~l~c~lt;~lgl.ot11) of li~arcls~vitlli~l 30 (lays (Ll) 50/30) w;ts 1000-1200 r. 1)os;rgcs ol' 450 1- were t~setlin both heltl expel-iinents. 'I'he 11losc ol)vior~scllet t of tllc r:ttli;ttion (see Tinkle, l!)(i5n) w;ts on 11;tl;tlity (T;~l)le3(i). /\Itel. ~.:~cliation01' ;ttlt~lrson ;II.C;I I ;it tllc onset of tllc l!)(i2 brceclillg sc;~so~l(1\/I;t1.e11), LII~ rl;~l;~li(y tleclinccl by ;tl~r~ost50 per cent o\~rtll;tt ol l!)(il. N;tt;tlity in the c.o~ltrolpol)ulntio~l (area I I) ;rlso ilec.liilet1, 1,111 by less tll;~n25 j)cr c,e~~t.111 ~hrI!)(i,l s.v\~itclibackcxl)eri~lic~lt ~.;ldi;~tion w;~s;~tln~inistc~.etl to ;~tlt~lts ol' ;tre;l I1 ill kliu-cl~.The n;tc;tlity tluri~lgthe sr~l)scclt~entb1.eetlillg sc:~so~ltlcclinetl lly ,I0 ])el- cent o\w t1~1tol the previous ycx, bt~tn;rt;~lity on the c.o~lt~-ol;II.~;I arc;^ I) ilecli~~cclo~lly 15 per cent. 7'1~ clcclinc in t~at;tlityw;~s ~)rol)ably ;ttt~.ibt~t;tl~le, in ~I;II.L, LO LCII~~)~I~;II'~stcl.iliz;t- ti011 of ~lle;~tlt~lts. So~llc nlut;ttio~ls 111;1y ;11so Il:tve l)r.e~l~)~.otlt~c.etl tl1;rt wcl~ lctll;~lto the ollsl)~.i~~g1)1,ii)1. to ll;tt(~Ili~~g.No i~i(~~.e;tseill the l'~.eilt~e~lcyof ;tl~~~o~~~~~;tlities;itllot~gl~;~tcI~li~~gs w;ts ol~sc~-\,c:cl. 011c (.OIISC~IIIC'II~.C01 ecologic.;tl iliillo~~tariceT~;IS tllc ell'cc.ti\,eness ol l.;ttli;ttio~lill ~.ctlt~c.itrg~~at;tlity, i~~tlcl,e~~tlc~lr oS ;ttlult tlcnsity, ;tlitl might I)e tlsetl ill l'11111rcficltl sttltlics Sol- this j)lll.l)ose. Otl~crell'cc.is of l.;~tli>ttiotlwere nlo1.e s111)tle 111;ln tl~;~t011 ~l;~t;rlity:t11(1 111;tlry Intlst Il;rvc occ111.1.ctl tllat were nor tlerec.t;~blebcca~tsc of tllc n;1trI1-c oS ficlcl cl:tt;r. For cx;tnll)le, \i;t~.iationsin g1.owth 1xte were obscrvecl ill tllis stutly. 1'0 selxt~-;tteell'ec ts of l.:t(li;~tio~~I'1.oln othc~.envil-onnlcntal i~lflr~enccs 011 g1-owtll r;~tewo111(1 1.equi1-enlo1.c corltrol o\.cl. field c.o~lelitions,1;11.gc1. s;~nll)lesol ;unill~als,;111tl ~l~nllel-ous~.eplic;ttions ol' the cxl)c~.i~llents. 'I'h~.ougllor~ttllis stutly 1 h;~\,e~)~.cse~ltetl cl;~t;t t11;tt may intlic.;~tcresitlual ~.atli;ttiotlelr'ects, :ttltl solrlc of tllesc. w:tl.r;tllt lul.tller tliscttssio~l.Sonlc tlilt;~ c,ot~lelI)e selcc.tctl I'I,~II~tl~osc ~)reselltr(l or1 grotvtll to incl ic;~tr;I lowc~growtll ~xtc;rnlollg jt~\ienilcs protlr1c.et1 by ]);tt.cnts rll;tt were i~r;tcli;t~cclin l!)(i2 (:tl.ea I). how eve^., otl~el-el;~t;t cor~lcl bc selcc.tet1 to stlow ;In i~lc.rc;~sccl]-ate, :tt least it) fenl;tles (FI';~l~le7); I'u~.thernlo~~e,siir~ilar cl;~ta c.ot11tl be ob~;tin~tl I'~,orrlthe cor~t~.ol:tl.e;t. 11' i.;rcli;~tion~)~.otlt~tetl any ell'et.~011 g~.o~,\ltllthis was 1i1;1skc(1by I~OI.III;I~\,;t~.i;~rio~l in g1.01~t~111 I.;IL~!s. Ill'ects of I-ittliittion on Ilio\,elrient sc.eln c.lein.ly intliret t. l'lle low n;rr;~lity ill tllc irl-atliatetl ;Ire;i in 1962 w;ts not s~~flicientlycompensated 11y inc.re;tsetl iln~~lig~.;itio~~to ilvel-t :I tll.ol~in tlensity ol' nearly 50 pet' cent between I!)(i:! i111c1 I !)(i3. bIci111 ~.et,iiptt~rc1,;1(lii :III(I ITIC~II~(Iist:~nt.e bet wee^^ (.;~ptt~r~>sl)otli i~~c.~.c;tsetlon ;tre;t I ill I!)(iY t:on~l);t~.ctlwit11 the p~.e\~iousyear. T'hesc inc.~.c;~scrl IIIO\~CII~~IIIS ;t~.e (.o~.~.el;tte(I with tlec~.c;tsetl tlerlsi ty, so arc i~ltli~.ec.tly;I[ t~.il)- t~t;~ljlclo ~.;~tli;ttion.Howcve~., in l!)(i5, no sucli cor~.elittio~i(.;III I)e tll.;twn; rhe tlc~~siry01' ;tclults w;ts so11lewh;lt Iligliel on the cxl~e~~imc~~~r;tl;trc;t 111;111 011 the (~)~itrol,Ijttt [lie nlc;111ret.;11)~111.e I-:I~~IIS i~~(~re;tsc(l 011 110111 ;t~.e;tsl'1.011i I!)(izl to l<)(i5.'l'he 1ile;tn tlist;rnc.c betweell c.;lpttll'es inc~.e;tsedfor ;1tlt11t11l;tlcs ;tntl fc~li;rlcson the c.ont~.ol;tl.c;t 1'1-0111 19(i/l to l!)(i5, but clecline(1 soniewh;~~ in ~n;~lesancl inc.re;~setlg~,e;ttly in l'enl;tles on the experiment;tl ;tre;t. These \r;tri;tl)lcresults ill the two expe~.ilne~~tsillust~.;tte the tlillic.~tlty01' ;~sc.ert;rin ing avllic.lr ellec.ts if ;tny 1.cst11tctl11.0111 ~.;t(li;ltio~l,bt~t intlirect effects il~.e;kt 1e;tst intlic.;ttetl. 'I'1rcl.c w;is II~indic.;ttio~~ ill citlrer cxl>crinlent th;lt the young frol~i i~.r;ttli;~tetl1);Irents showetl lower su~,vivorsllil)tlian young of the collt~,ol ;~niln;tls.Survivorshil~ wits ;tl)ottt the sitliie on botll ;uc;ls in e;~cllol the ex1)el.i- ~ncnts;tntl was ncitlle~.the higliest nor the lowest observetl in the scvcritl yexs of tllc stutly when st~r\~i\~o~.sl~il)csti~rl;ttes were not co~~ll)lic;~tctlby ~)ossiblcri1di;ttioll etl'ects. 'l'he tlat;~011 immigr;ttio~r likewise g;rvc no llirit of r;~cli;ttion eft'ects. i\ltlro~~gli1)op~rl;ttion tlerlsity was greatly lowerctl on the expcriment;tl ;trc;t irr 1963, the evidence intlicittctl th;tt the 111-oporlion of imrnigl-ilnts ;ttrlong the resident breetlers in t11;1t yeitr wits ilI)o[lt the same on the exl~ct.ime~it;tl ;tntl c.ontrol areas. The sex rittio W;IS not ;tllectetl by r;tcliation ;IS Table 43 intlic.atetl, 1111r other ;tspects ol pop~~lationstr~1ct~11.e e\iitlcntly wci-e (Tinkle, I<)(i5tr).71'llc low n;it;iliry on the experimental are;t in 1962 resulted in few sul-vi\iing oll- spring. I'he vai-i;tnc.e in nt~~nberof st~~,vivingoffsl~ring protlttcetl by c;tc.h I'crrri~le~~;u.ent W;IS low. This wits cll~itein contrast to the sitt~atio~ion thc conlrol ;Ire;r. Assuming tll;tt ;I tlilferentii~l in tlie protluction of st~i-viving oll'sljring is intlicative of tlrc tlilfercnti;~lin competitive ;ttlvant;tge ;Inlong the v:t~-io~~sfcm;~lc I~rectlel.~, we (,;In concl~ttletll;~t the normi~l1)roc.ess of ~iatt~~.;rlselec.tion w;rs thw;u.tetl to sonle extent by the r.;ldi;ttio~~. 111 sulnln;u.y, ~.;~tli;ttionlowe~.etl n;~tali~ywhic.11, in 1111.11, resultetl ill ;I lowel. tlcnsity ol ;rtlults tlre following year. 'I'lle lower tlensity resulrctl ill ;I sccontl ye;tr ol low n;~t;tlity. In ;~tltlition,the efiec.tive popu1;rtion 1)reetlitlg siLe w;ls ;tltel.etl by tlle low ~~;italityo~i the experimental ;flea in 19(i2. 'l'hcse ;u.c tlie only t1e;trly evitlen~cl1'ec.l~ of ~.itdi;ttion,tllough influe~lcc011 111~ nlovcnlelrts of indivitlrr;rls by tlle intlirec.t effects ol ~;tcli;ttion on tlensity w;rs SII~]'".L"'I. l'rrr~tre~.,Hotltlenlxtcl1, ;tntI L;tnno111 (I!)(jr)), working wit11 [Jtfl S((I~IS- l)iiri(iii(i ;it the Nev;rtI;t 'I'est Site, I'OIIII~L no v;tri;ttio~~sin growth ~-;ttesof li/;rl.tls LII;IL c.or~lclI)e ;ttt~.ibutedwith c~crt;rillty to the c:llronic irradiation OIIC01' t11c clist;tt~tobje(.tive~ of nly str~clies01 [lie l'exas l~opulationswas to ~~'cclictwh;t[ tlili'el.enccs ill clc~nogritl~hyriiight oc.crlr. in tllat area of the 1.angc ol' '(JI~.s/trt~.vhrrr-icit~ti ~vhcre cli~n;~tic contlitions were quite different I'I.~III tl~oseol T'cs;ls, lor- es;tull,le, ill the IIOI.~~I~I.IIl>:u.t of tlic r;rnge w1le1.e ~~i11te1.s;IIT 111o1.cr.igo1.0~1~ ;111(l the gro~~ingS~;ISOIIS ;t11t1 r.el~t~ocI~~tiveSC;ISOIIS s1101.tc.1..'l'l~e tlcn~og~.;tl)llic er~~~ir~ortn~e~~t is ;rn i~nl)or.t;trlt (.on11)011ent oS the tot;rl sclec live 1)rcssllres oll incli~icll~;~ls;rntl tlescrvcs tlet;rilecl conlparisons. One nligl~t1)re(lit.t, I'oI. ex;t~nl~lc,tI1;tt nor.~hernliz;trtls rlligllt h;rve a lower birth r;rtc I)cc.;tltse ol' tllc shortel rel)rotlrrctive sc;tsor~.Unclet. slrcll contlitions II~;I~II~~II;III~.~ol ;I c.otlstallt ~)o])ul;rlio~lsi/e wottltl l,eq~lirca lower- cleatll r;rte L~I;III l)rc\~;tilsin '17ex;rs. 'l'l~is worrlcl, in tr~rrl,1c;ttl to a difTercnc.c in tl~e;tgc struc.ture ol' the nortller-n ant1 l'exas popu1;rtiorls. I chose ;in ;tl.e;r ill northwcste~~n(;olor;rtlo lor st~c-11a stt~dyancl decitlctl to collc,elltr;tte on only ;I few ol).jcc.tives. No attenlljt was m;rcle to study the ~x)~)ttl;rtionsin C;olor;rtlo :IS i~~tcr~sivelyor ;IS l~rontllyits w;rs (lone in l'exas. -1'ho sttttly ;t~.c;t\\,as the s>trne six ;IS those ~rsccl in Texas, ant1 was 1oc;rtccl irr <:olor;~tloN;rtion;tl h'lonumel~t,i\iIes;r Col~nty,(:olor;tdo, \TI-y 11e;rl. LIIC Ut;tI1 l~or(Ier..A 1.;1~11ergross ext1-;11)ol;r~ionof the comparati~re cli~n;ttic.contlitiorls between westc~-11C;olorado ;tncl western Tex;rs h;~\*c I~ccn~;tken lrom Visllel. (1!)54) ;tticl :tr.e sl~ownill T;rble 52. The figures 211-e c~ucle,brrt the coml)a~.isor~1c;tves little tlol~bttl~:~t the MJ~IICC~S;II-~ 11101-e rigo~.o~~stI~;t~l in '1'es;rs ;t~itltll;tt the ;rc.livity season for the ut;rs is allnost c.c~.~;~irilyshot.tcr.. V1or.c 1)t.cc.isc tl;~t;r :rrc av;ril;tble I'r.orll lot~g-~c1.mrecords kcl,t at tire wc;rtlrcr st;rtiol~it1 (:olo~.;tclo National NIo~lt~rnerl~;tl)otrt 3 miles from rrly stutly :rl.e;r, 11t1t ;rt ;trl clcvation 2000 feet Iliglic~..l'lic 25-year aver;rge (1!)~10- (i.4) snowf;rll MI;IS 4 I inclles, near the extral)ol;rtctl ligrtre in '1';rble 52. 'I'he 1rlc;rrI J;rt~tr;u.y~ninimlml w~s 1'3' 1; ;r~ltltlle nle;ul n~;rximun~370 1;. 'I'he ineall ;tnrlu;rl ~)r.ecil)it;~tion1v;ts ;rl)out 11 inches. is 11~ol1;tl)ly11ot locate(l ill ol)tirrlrrn~h;rbit;~t, which appa~entlyoccllls in the TAR1.E 52 A C:~~II'AIIIS~N01: SOMEGROSS CI.I~IAI.IC UIFI:I:KENCI:C I%I-I.\VELN iV1:s.r EKN C:OI.ORAI)O ANI) ~\II:STI;RN 'I'Es. - - -- .------~ - -~~ --- ~ - 1tc111 Texas C:olorntlo - . -~ Isoll~c~~III (iO" 1; 50" 1" ( ~YI.(,I~III:I tic: (,l:~shiIica 1io11 llol SIIII~III~,~; Short and 11ot llot 111iltI wi~itcr SIIIIIIII~I.;cold ~vi~~tcr (;~,II.( I~III;II~~~,i,gio~~ (I No1 111;11 ~;III.(I;~ily III~II~III~IIII 30" IF (x = /Illo 1;) :];I 'I I.' (X -- 20" 1) Nor111:t1];III, (IiiiIy III:IX~IIIIIIII 50" 1.' :{so1; l);~tcM~IICII IIOI.IIIJ~ ili~ily~~IIIII. I iscs ;~l,ovc~50" 1; I .;ttr. Fell. Early A1)1-il l);~li,of 75 [)[,I. i.c111l~~ol):~l)ility of IIO l'lo~ti11 &[)I i11g blicl~l~el). h~liii-kI;~i~i11 No1 III;II II-II~I11 01' f~~ost-f~,ci>&~,;ISOII 215 (l:~ys 175 (lays ------~-- bot~ltlcl.stl.ewrl ~.;~vitrcs.Suc.11 ;~rc;ts~vor~ltl be tliflicrtlt to work; c;tl,tr~rc of ju\~cnilcs,I'ol. ex;tnll)lc, wor~lclbe cxtl~elnelytliflic~~lt. 'I'he ;Ire;t wits, instc;~tl, I;titl out ;~c.~.osssornc 1.oc.ky ;u.i.oyos itnd hillsitlcs that arc I';~vorableI~;tbit;~t, IILIL il~c.lr~tlctl;~l)ot~t 50 ])el. c.ent s;tgel)rush H:tts in wllich ut;ts wel-e scltlo~r~ COlltltl. 'l'llc ;II)~)C;II.;IIIC.~oI' the s~tbsl)ecicsin (:olor;ttlo (PI. 1V) (ti. .s. .sltr~r.vh!r~.- i(itrtr) is c111itc difl'el.ent I'1.olll that 01' tllc 'l'exas ~-;tc.c(Il. s. stcjrlegc,).i). 'l'lle (:olor;~tloli/;~l.tls ;u.c ;t tll.;tb g~lyto brown wit11 almost no tlol.s;tl 11lal.kings exc.el)c for tllr I~;tntlson LIIC 1;1i1. Sexual tli~no~-l)l~ismis minimal. 'I'lleir re- tluc.ctl w;~riness,c.onlp;tl.ctl ~,vithrllc Tes;ts li~:~rds,matle thcln e;lsy ~o c;rl)- t111.c.'1'11(~ I~;I 11y t li llc~.c~tlc.csill ~;II[elm, lrio~.l)lrology,;tncl bclr;tvio~.of tllesc I< II).I.I I,I< ;\SSO(;I,ITI.:Sox TI (k)~.OU,IIN) ,\uI~;,I.-~I I ;IS ill-c ~i~~~i~e~-ic;illy tlomiti;~titon tlic stu(ly ;II.~;I, Ijr~tse\.c~.al otllc~. sl)ec.ics ;Ii.e prcscrit in fail, ti~~~iil)c~~s,i111(l it is 11ot so siri1])lc to jr~clgctliei~. re1;11i\.c. ;II)~II~~I;II~(~c ;IS it \V;IS ill F1-ex;is. ~~IIO~III~/~/I~IO~II~Stigris, ,YC(>/~/I~I-II.S I~II(/II/(I/I~~s, (;II(~II~~(/O/~~IO~II.~ ~I(*/o?c, Crot~f111~llr.s 7l)i~liz(~t1i, Crot(~/~I~y/~r.s (.o/I~ri~ ;11ic1 1.'ro.s(rIII.I~.S or11(1111.s ;Ire ~)~-csctitin ;tl>or~ttli;~t ortlel of' ;~l)untlit~ice.S(.c~lo/)or/rs grtr~~io.srr.s is cx- 11.c111ely;II)LIII~I:II~ I it1 1)1;1(~t:s1ie;11. t lit> s111cIy ;~~-e;i,1111 I IV;IS IIC\~CI-t~;~])tt~~.c~cl ~\.itliitiit. 01iIy olic spec.ics ol' s~iakc, l\ltr.slic~o/~l~i.s/N(,II i(rt 11.s.IV;IS seen ill t lie strlcly ;II-C;I, ;inti it is I';~i~.lycornnioli t11cl.e. Otlie~.sli;~kes i11.c tlot~l~tlcss])resent ~II tililcs 1.01- tlic)~Iii~\.c 1)celi c';~l)tt~~'ecl~ic;tl.l))-. T'l~csc i~ic.lr~tlc I'itriofil~i.~ c.t~/(~r~!((,r, (,'rot(/111,s ~liri(/I.v,~ 1-IIKI l.'e111;11cs~vi~l~ ~ --- ~ ~ %--3111111 1-7 111111 follicles folliclcs -- -- I 4 55 26 34 I '1 28 :i I 3 I (i 13 0 2 0 0 10 50 14 55 20 25 2(i I (i / 82 ])el.~cnI 1)osI rc.l)l.otlucl ivr. 11;rtl (-OI.~X)I.;I Irr~c;~,tlefiltitc i~~tlic.;ttio~~stl~;rt th(.y 14~cl.c.laying ihci~.first c.lutc.ll ol' the yc;rt.. One-11;1ll ol the l'e~rl;~leswere l)ostrcl)~-otlut~ti\~cby mitl- ,Jlrly, ;~ntl82 per cent by ,July 23, l!)(i5. 011 the basis of tllis inlormation I wollltl say thal the enlargenlent of the ovarian lollic.les commences ;rbout ~ilitl-l\/l;n-c.ll;rntl cntls abou~mitl-Iuly. Assuming th;rt ;rbo~rtone non nth is 1.ccluirct1 for e;1t11 c-lu~c.h,there is s~rffic.ienttinre lor c;rc-I1 female lo 1;ry cl~~.cc c-l~~tc.licstlnring tl~c~.el)~-otlrrc tive season. Nothing (.;III I)e s;ritl ;it II1.csent ;rbor~tthe f;rcto~.sthat ir~iti;~teor terminate the cslrous cycles. The actual data available on the reprotluc~ivecycle are shown in Table 53. One J';~ctno1 sllown in tl~etable is that Srom one to 21 per crnt of the ;unimals in each saml~lehat1 both recent (01-por;~lutc;~ al~tl yolkecl lollicles, 111-oviding prool for inr~ltipleclrrtclles. Note that on M;ry 27, sixty per cent ol the lemales hacl yolkecl t'olliclcs; ovr~lationoS these wol~lclbe expected in the next two weeks. 7'h:rt this was the c;rsc can I)c seen from the sample ol ,l~rnc11-12 ill which the inirjority Ilatl ovitluc:rl eggs. The next salnple of ,[rlile 24 showetl the 1n:rjoi.ity ;rg;~inwit11 yolkecl lollicles. In;rsmr~cli;IS about oiic ~no~itlielal~sctl betwee~l thc May 27 :rntl ,Jrr~le23-21 s;rrnples, in I>oth of wl1ic.h the majority of fem;~leswerc in the same ~.el,l-otlr~ctivestage, this m;ry bc c.olisitleret1 the axrer;rge time between c.lutches. Illc earliest sample ;~vailirl)le(iipril, I!)(i(i) cont;ri~retl;rl~out 25 per ccilt immature I'emales co~npa~.ctlwith about 7 per cent in tllc c;~-lyMay samples. l'he lil.st-c1utc.h n;ti;~li~yis ~,rol~al~lycoiisitlerably sin:lller than the tlieo~.etical ~r~;iximrrrnbcc-;~r~se ol the 1)reserlc.e ol' so ma~lyiinm:rtrrre irnimals ;I( the onset of tl~c~.el,~.otI~rctive seirson. FAI S,ro~ci~c;~.:KY (:OI.OI 'I I~in 'I lri~~ 'I 1li11 'I hin 'I hill 'l'hi~~ ,:. .III~). . tl~ith l.';~i~-Iytl~ic.k Seven :~tlult fenlalcs collectetl in Scl,trml)cr anel 0c.loljcl. l1;1(l a mean l'irt I~otlylcngtl~ ol 9.0 111111, ant1 the fat botlies v'crc (llrite thick. All 01' these tlata intlic~rtethat increase in six ol [;it I)oclies is coinc:idcnt with the cess;r- t ion ol' rcl,rocllrction :untl that the si~c01 S:rt boclics in the f;rll is Inore t1i;rn tlouble t1i:rt (luring the 1)rcetling season. 'l'herelore, tlie 1;rt I~otlicsm;ry bc iilllx~.t;riltill the ~.elx.ocluctioliof (;olol.atlo 1ix:rrtls jl~stas wits the case in Texas. I Si~c.g~orll, :I',-:il) 111111 40 I I 15-4 1) ,\[)I ilRl;~y 2.S (12) .3.3 (77) 3.9 (38) jr~~rc-,Jr~ly 2.5 ( 1) 2.9 (71) 3.2 (5 I) bl'e;~~~:III(L 'l-ot:~l 2.7 (16) 3.1 (I IS) 3.5 (92) ~\sill the T'csas j)ol)(~l;rtion1l1c1.c is all i~~c.re;rscin t11c nlc;ln c.lr~tt11 si~c will1 inc.1.c;rse in si/e 01' t11c Ic~n;rles.'I'l~e mean clt1tcI1 six is allnost one egg g1.e;rtc.l- ill tllc largest tl~;rn in the s~n:rllest six c-l;ras. 'l'hc cl~ttchsi~e 1;1tc1-in tI~c~.cl)l.o(lr~t tivc sc;rson is s~n;rllc~-th;rn in tllc c;r~-lyI);II.~, ;tntl this is 1101 I)ec.;rl~sctllc len1;llcs co~nl,~-isi~lgthe 1;rtc sc;rson aanlj)les ;Ire slu;rlle~.. Fl'llc s111;11lcstsi/c cl;~ss(35-:)!) mni) con1111ises 0 pel- c.c~~tol tlie :\pi-il-May s;r~lll)lcs,o~~ly 3 ],el' cent of those in ,Jt~ncant1 July. The lai-gest six class c-o~r~l)~-isctl50 ])el. (.en1 01' tllc Al)~.il-ILliry s;t~nplesant1 112 per cent in J~lnc ;lll(l ,111ly. 'I'llc 111e;rn c111t(11si/~ 101. -10-.1~1- ;111(1 -15-4!)-1111n fem;rles is ;~houtthe sallrc in '1'cx;rs ;rntl <:oloratlo. 'l'hel-e arc no III;ILUI.C I'em;rles in 7'ex;rs ill tlie :i%-.bi!)-~~inlc.l;rss ant1 II~II~in the 50-5,1-11lrn (lass in (:olo~.;rtlo.Thcl-clol-e, the s~n;rllsire oi' the <:olo~.;~tloli~;r~.tls 111;ry l)c ;III iinl)o~t;rnt I';rcto~.ill the sm;rllcl. cl111t11 si/c in this ~)ol)ulation. If c;rt lr (:oloi.;rtlo Icnl:rlc 1:ritl 3 t ll~tc.llcsol ;rvel-agc si/e, ~\rhith wol~ltl see111 to 1)c the nl;~ximurnn~~~nbc~. ol t 111tt llcs in the sI1o1-t 111-cctling sc;rson, tl1c11(Ire l.el,~.o(l~~c.tiverate wo~~ltlbe ;rl,o~~t9 eggs ])el' lem;~lepel' genci.;rtion. However, tlris p~-ohal,lysllorlltl be 11c:u-cr 8 I,cc:r~tse of the 1;rrgc nlrrnl~er01' imn~;rtr~~.cfen1;rles in the ~~ol~ulationat the ollset 01' thr repi-ot1ucti1.c season. 7'1iis csti~n;~teis srn;rllc~.th;rn thc ~nininlr~rnof 12 cggs I)el' l'ernale ill Fl'cx;~s. 71'l~cfirst eggs \\lcre c\,itlcntly 1;ritl in ~nitl-~\])~.ilin I!)(i(i in;rsrnlrc.l~;IS lloile ol ~hc1'clrl;tles c.ollcctecl on 121,ril ti-!) llatl 1:ritl ~.ccently,;111tl only 2 c.ontained ovitluc;~leggs. \l\ie were not on the stu(ly ;ri-e;r when tllc young lir;r~.tlsIl;rtc.llctl in [!)(if, bl~tin l!)(i5 the first h:rtchlings ;11)peal-edne;ri- the ;II.~;IOII 111ly 23, ill tl~c;II-e;r OII ,July 25. i\ssr~rni~~gthe time 01 first egg-laying wits ;~l)or~ttl~c s;ume in I)otli years, tl1e11 ;I ~)c~.iotlof l)osttlel~ositio~l;rlclevel- ol)1n01t ol' tle;~l.ly100 tl;rys is indic-:rtecl. 7'his is ;rl,o~~tone rnontl~longer than in '1cx;ls. \Yhcrlle~-tl~c ~)crioel ol tle\~clol)rncntis I-e;~llythis long or whethcl- t11c li~.steggs 1;ritl siinl~ly(lo not h;~tcllis not known, bul the first allel-n;rti\.c scc~lr:,111o1.c likely. ~1.11~:<;l ]'I(.. 20. Si~rgc-or~l)s ITI-cssent :illlong ~~c;u.lictlIllas on tlcc (:olot-;rtlo htrrtly ;ii-r;l for ccc-tain cc~ontlcs!vlr(.n c-cli;cl)lr tl;tt;~wrrc ;c\;rilal)lr. ill~sciss;~slcows srrorrt-vrc~tIrrigtlr it1 ~~cillicc~ctcrs; or(Iicc:tte sl~o!vs IIIIIII~)~~of i~~~li\~i~Irr;cls. '1.11~left Icistogr:t~c~is for Jt11y ;r~i(lAlrgtrst, ICKj5, riot icrclr~tlirrg tlcc. ;~tlrrlts.'l'lce RS-IIIIIIrecor(l I~clot~gswith this Iiistogracii. Tlre right lowcr Icistogr-;c~ciis foc- May. I!)(i(i, ;uitl inclrctles tlie 37-IIIII~intlividual. 'l'lrc rig111 upl>cr 1iistogr;ltn is for ,111nc, I!)(i5, ant1 JIIII('. I!)(i(i. Solid ;I~CIISirrc IIILLICS. OIICII arc;^^ fc~iiirlcs. SCC lrxt for :~(l(litio~i:~lex[)I;~~r;rtior~ ;clicI (Iihc~ch\ioc~. not kirown, ;rltho~~ghsumc Il;it(.llli~~gI~I;I~CS ~lr;rrketl iir late July hat1 re;rchetl 4 I llllri by early October, so some ol tlrern probably mattire ulithin three ~nontl~salso. -1'11e 1'irc.t that a;r~rll)lcscollec-tctl in April for the strctly ol' 1.e1,l-o- tlr~c-tionc.ont;ii~~c(l 25 j)cl' c.cllt ili~lr~;itul.cl'cm;ilcs inclicates th;rt rnmly 1;1tc Ir;~tc.hliligstlo 11oc I1l;rlrll.c bclol-c tlrc sl)i'ilig, ;~plxoxi~~r;rtcly!) molltlrs ;tl'te~. I~atchirig. So~rleclata l'roni the nlarketl lizards have a bearing on estimation of the age ;it maturity. 01those rnal-kccl at hatching in 1965, or at least very near the 1 ITT' Akl) l)LRIOC,KA1'111 Or IJTA 159 ti~r~c01' h;rccIiing, I I nl;tlcs ;t~ltl11 l'clrlales sr~rvivctl111rtil Ot c~hcr,;I[ least, when ~lic;rrea was wo~.ketlfor the 1;ist tirnc tll;tt yeitr, but M1cl.e not reco~.cletl on the area in I!)(i(i. 'l'l~cscli~arcls hat1 I-eitchetl, by October, a meiun length oS 35.7 mln ( 6 8 ) ;tntl 32.8 llllrl ( 9 9 ), SO were still well aliort of mature size. It might I)c ;tr-gttetl 111;tt thehe li~al-tlstlitl ~~otsl~rvive to maturity because they were not lo~~ntlill l!)titi ;rncl t11;11 tllis TV;IS ;I ~I-~II~Igrowing at a slower r;ttc than the or~cstlt;lt tlitl SIII-vivc.This is not the c.ase, lor :111 thc 1iz;ircls 1li;tt cliel artrvi\/c to tllc I!)(iti l)r-eetli~~gsc;rso~r 1i;rtl been tllc s;lme si~ein Oc.tol)c~.;IS the no~~-strl.\,ivi~~gli/ar.tls. Nine m;~lcs;~vcr;~gecl 35.3 nlln in lcngth ;111(15 l'e111;11es~IVCI.;I~C(I .32.8. 7'urelve ~~i;rlcs;rrltl I I females th;tt were mill-ketl for the first time in 0c.tol)cr. ;rveragecl 30.2 ant1 3 1.3, resl)ectivcly. The me;tn six in 0c.tol)cl- ol' yo~tn:;-ol-tlie-yc:~~.~ll;rlcs, using :111 ot the tl;rt;r ;tbove, ~v;ts33.5 (22 ~.ec.o~.tls);111(1 01' Se111;11cs.32.2 (25 recor-(1s). 'I'he c.~.itic;tlcl~~cslion is 11ow mtny ol tllese li~al-cls1\:o111tl c-o~ltinlleto gr'ow ;~l'tc~-mitl-0ctol)or- ill Coloratlo ant1 1.eac.h ;rtlrllt si~c1)rior to the onset ol' tl~c~.cl)r-o(lr~ctive sc;rso~l lllc following i\l)ril. 0111- ~.cc:ll)t~trecl;tt;~ ;tr-c not s[lllic.icllt lo ;tnswcl. tllc clt~cstionslor tllc ;trc;~was wo~.kctllor the 1;tst time in l!)(i5 ill ~nitl-Oc.tol~c~.,;111tl work wits 11ot ~CSIIIII~~~IIIIC~~ 1;rtc May of I!)(i(i. I-Iowcvcr, the bile tlist~,il~r~tio~lof 1i~;rl.tls collcctetl lor the rej)rotl~~ctivcstutly oli :\l)~'il8-!), I!)(i(i, ])I-ovitlctlan ilnl)o~.t;r~~tc.111c. Fl'l~is si11nl)le was c.e~-~;ti~~ly 1)i;tsctl in f;r\!o~.of 1;11.gcr.Ir~tl;tlcs I)ec:tr~sc of the ~)ur-j)oselor ~vllicll (lie collcctio~lT\~;IS I>eing 111;ttlc,so any cstirn;rtc! ol the fl-ecjucnc-y of imm;rture ;tni~n;tlsin tllc ~~ol)ul;~tionrn;r(le 1'1-omthe s:rnll)lc will bc ~r~ir~irrrcrl.Ever1 so, 10 of the 40 fern;rlcs in tile sample were i~nmatrtrc.0u1- survivorship data i~ltlic;rtc111;rt :tmo~lgtlic ;rtl~rltlizal-(ls, ;I tliirtl or 1nor.c were two yc;tr-s oltl or- oltlc~..Fl'l~crefol.e, wc may asslliile that ;rl)o~lt25 of the 40 li/artls c.ollectet1 were yc;trling ;~nini;tls;rntl 10 of tl~cscwere i~nn~;rtru.cat the o~~sctof the ~.cl)rotl~~ctivcseason. As st;ttecl p~-e\~io~rsly,this is ;rls~iostcertainly ;I ~lli~rilnl~lll cstitn;ttc, so tllc prol)o~.tionof tllc ani1n:rls h;rtc.hetl in I!)(i5 thi~t11;rcl reac.hctl ~rl;~tu~-ity;IL tlle st;tl-t oS the I!)(i(i bl-eetling season may 1i;r~~been only 50 ]>el'cell 1. TliercUore, cvcrl tlior~ghthe <;olol-;~tloliz;rr.tls rn:rttli-c wllen sin;tllc~.,;lntl 11;1vc;tplxoxin~;rtcly ~lic s;llne jil-owlll I.>rte ;IS tllosc ill Tex;rs, they ;rrc still not ;ill able to reach maturity by the onset of tlie 1-eprotl~tctiveseason because lllcy llatcll late in tlie sulnrner ancl have a shorter growing season than those in Tcx:rs. These data will be tlisctrasetl 1;tcer in connection wit11 the evolution of rcl".ocl~icti\~c~-;rtcs in tllesc r~t;rs. 'I'III,:UL'.III\VIOK 01. (:OI.OKI\I)O IJT!\s.-LJL;Is ill (:oIoi-;rdo ;ri-e much less wary th;rn chose in Texx ;illel use clle asserlive Imbbing tlisl~laymuch less l'reci~~cntly.1nter;rctions between indivitlu:~ls are less often seen in casual ;~ctionsI~etwecn intlivitl~~;~ls wc1.e ol)servccl. From May 31-,June 2, I!)(i(i, i~lclivitll~alli~;u-cls ~II rllc <:olo~-;~tlost~~cly ;rr-e;~were lollowetl by 4 obsc~.\.ersthl-o~~gllor~t tllc (lily. Silllil;~~.l)ro(.ctl~r~.es ~~erc(;~rrie(l o11t 011 ,J111ie8-!) cluri~~gtl~c 1;ite cvc11i11g;III(I c;11.1yino1.11i11g. LJt;ls ill (I~is;II~;I (lo 1101 I)ecome ac.tivc ;IS c;~l.ly;IS those ill 'l'cx;~s.Higll h111ll's lo the c;~stsli;ltlc 111c st11(1y;tlCc;l 1111til ;11jo111 7:OO A.M., ;111(1 ;I Iligll tlli~~ c.lorltl covel- is I~.ecl~lc~~tlyI)I-escllt tlr~l.i~~gthe sulrlrnc.1- 111o1.11illgs./Is ;I 1.cs111t of tl~escf;tctol.s ;~ntlthe cool c:u-ly mor~~ings,III;IS ;IIT 11ot ;I(.[ i1.e IIIII il 8-!) ,\.PI. As in Tex;~s,they spentl lrtost of tllc time Ixlsking ;III(~ lcc(lil~go1)1)01- t~~nis~ically.Dtrri~~g tl~e ~nitltlle of tllc (lay, 11lost of them seek sheltcl. I)enc;~tl~~.ocks, 1)11t l'cn~;~les;Ire I';II- nlor-r likely tl1;111 111;ilcs to I)e b;~ski~~g tlul-ing tl~eulitltllc of tl~ed;~y. 71'lle ~:ILIII-Cof the 1;111tlsc-apeblot ks JII;III~soci;~l illtel.;~( tiolls. LJt;ls 11.c- cluc~irly1);1ss i11 close proximity witlio~ltseeing one ;~notl~c~-.It W;IS 1:u-gely on rllc b;~sisol' llegative illforrn:~tion on soc-i;11 intelxc lions ;111cl 0x1 the b;lsis 01' I;ll)ol,;~to~.yI)ell;~viol- th;~~ I 1i;td forlnetl the opiniol~(7'inkle alltl \i\Tootlw;rrtl, l!)(i7) t11;tt the utas wcrc not terl.itor-i;ll an(l t11;lt this w;~sone of the ~rl;~jor- I.c;lsons for the I~ightlegr-ec of home range o\,e~.lapon the st~~tly;rre;l. 1'0 test ~l~c;rgg~.cssivc~~ess of the li/;ll.tls ~vcc.o~rltl 11ot tlcl)el~tlII~~II c.11;lnc.eobscr\/atio~i of tllc 1.;11-ei~~tc~.;~ctions. No11-1.csitlc11t 1ni11es ;111(l ICII~;I~CS were (:aught or~tsitlethe ;II-~;I, tied to 1o11gtl~re;~cls ;~ntL in 11-otluc.ctl ill to [lie visu;;l i-;ul~geof st~ltly-;~rc;r~.esitlcnts. In his 1n;tnnel. we I'o~~rltlth;~t li~;cl.tls of' I)otl~sexes (lo bell;~veaggr-cssively tow~;u-tlli~;u.cls ol the s;llnc sex. \4'c were ~11sos~~~.l)risctl to li~lcl tli;~t ;I m;~lcg;rvc ilnlnctli:~te intlic;rtiol~ol sex 1.cc-ogtli- tiol~clcsl)ite thc very low clegrcc of sexu;il t1imorl)Iiisln. \4'11c11;I 1.esitle11t~nalc w;ts co~~l'~-or~tcclwit11 a non-rcsi(lcnt III;I~C, il ;I~IY;IYS tlisl)l;~yctli~~~~~lctli;rtc ;iggl.cssivc rc;~c.lions,I~rlt im~nctli;~tcly be gar^ cor~l.tshil)ol' a I'cin:~lc. '1'1lc1.c w;~slittle clo~~l)~:~mol~g ;illy of tlle obscl-\,el-:,t1i;lt tl~cclegrcc 01' agg~~cssivenesssl~own by these 11t;rs was less t11;111tll;~t (lis111;1yc(I IIY the 1'cx;ts liz;~~-(Is.'l'lle rcsitlcllt seel~letls;rtislictl to clri\c tl~cno~~-rcsitle~~~ only ;I sl1o1-t tlist;~nc.c;IMJ;I~. 'I'lley (lit1 not persist ill tl~ei~.aggl.cssio11 o11c.c tl~c11o11-l.csit1c111 ~.clrc;~tctla s11ol.t tlist;~l~cc01- tlisl)l;~yccl;I s~tbrnissivc11ost111.c. St1c.11 I)cli;~vior is s~lggesti\,eof the existence of ;I soci;~lI~ier;~rc.lly, 21ncl 1 think LII;IL tl~ca\xil- ;111le c\ritlence suggests tll;lt sl~cll nay exist. l;il.st, ;IS rn;Illy as 3 males In;ly II;I\JC closely c.oligl.~~cl~rI~olnc I.;lngcs. Tinkle ;111(1 \~~O~(~MJ;IIY~,l!)(i7, w1.011gly intcl.l)~.ct(:(l tl~is;IS ;rl)sel~ccof tc~.l.i(ol.i;~lIjcl~;~\.iol.; instc;~tl, tllc o\,cr.l;111is j)c~-~nittc(l1))) the T~JC;I~te~~~~itor~i;~lil)/ ;III~~tolr1-:111(c 101. otlicr li/;~~.tlstll:~~ be1i;tve s~~bortlir~ately.Sec-ontlly, clrlring the sutnlllel. oC l<)(i(iwe observetl lirartls whic.11 ilnlrlctliztcly ran l~eneacli;I lack or quickly retre;~tetlat the al)lxo;~c.liol' ;I I;~l.gel.,t1ollrin;rllt ~ll;tlec\,cn I)el'o~-ethey T~J~I-ech;~llengctl by lli~n.'I'l11.ce enco~tnte~.~were obse~.vetlhet.ivecn inales of tlilfel-ent ages; in e;~c.hrlle older tnalc wits c1e;trly tlo1rlin;ullt. Three encotrnters were seen be- twecli li/;~t.(ls01' llle s;t~ileitge cl;tss. Two oL these were betweell lemales ant1 in t~eitllc~.insta1lc.e (lit1 one I.etl.c;lt even though one of' the enco~rntel-s 1.csrt1tctl in T'~~C)I.OIISI~gllting. The tllil-tl was ber~veentwo ~n;llcsof nearly itle~ltic.;ulsi~c. C)nc st~c.ceecletlill chirsing the otllel. out ol' irs ;tt.ca. 'l'llcsc tI;rt;u ;tl.c no1 ;I strong c.;lse 1'01. ;I social hier;rrclly, but they ;IIT ;II)OII~ ;IS goocl ;IS r11;1t ~~~'eviot~sly1,clx)rtetl Sol. tl;rtl~r;tlpol)t~l;utions. The l';rc.t th;tt it1 ;ill tlirec c.;tses ol intel.;tc.tio~isbetween yocrllg ;IIICI oltl tn;tlcs (;dl ;~tl~~lts),the yotlngc.1. one ~.ctre;ttt.tlwirllo~~t even rett~rtlillgtile c.h:tllcnge of lllc oltlcl. is signilic;~~~~.T'liis tyl~c01' 1)ell;tviol. w;us nor ol)sel.vetl in the rex>rs!;I tidy. Fl'l~is~)l.esr~lnccl Ilic.1-;t~.cllic.;tl ;tI.l.;tngemenL of the C:olor;rtlo li/;~rclscomes ;ubot~r,ill IIIY view. 1'1.0111 tile gl-c;rtc~-ovel.lir~) ol' age classes ~II;III occttrs it1 T'ex;us, ;tnd l'rolrl tile t~o~t-r;u~itlotiitlistril~~~tio~~ 01' goo([ h;rl~it;~tin the i~re;~. 71'l~esysrctrt, colnl~irt.~tl~~\~itl~ ;I s~l.ic.t tcl.l.itol.iill one, ;tllows higher densities to clcvelol) it1 tillles of higll I-esolll.cc le\~cls.7'1ie i~ltel~estingcluestioll is whetllcr ~.cgltl;tliorlol' t~r~~nl)e~.s11;ts ;~lso I1cc11 ;rcIiievetl in sr1cl1lliei.;rl.c llies by rcstric- tiotl 01' ~.c.l)rocluetiot~~)~'irn;tl.ily to tlie elolni~l;r~ltli/:rrtls. 1 clotrl~tth;rt this oc.c~r~.sI)cc.;tuse ;ill ;ttlttlr l'c~n;ulcs ;tl)l)e;tl- to 11c t.el)rotlu~ctive cl~rring the I)t.ectlirlg.ac;isot~. 'l'lle t1ill'el.cnc.e ill tlc~1-ecou ;tggressiotl 1)ctween li/;rl.tls of' the Tex;rs ;tntl (:olo~.;ttlo~)ol,~rl;utiotls 111;ty 11:tvc ;I genetic Ix~sis.In 'l'ex;ts ;I ella, generally, 11;ts ;I silrgle cli;rt~c.c to 1.el1rot111c.e.In (:olol.;ttlo, ;c s~tbr~iissivcintli\~itltr;tl, I)ec;ttrsc ol' tltc longer lile exl)ec.t;rllcy, 11;ts ;I gl.c;rtel. ol~portl~llityto rel~rotluce ill ;t~lotlie~.sc;tsor~. I'CI.~I;I~IS tttltlc~. stlc.11 c.i~~c~t~~r~st;r~icesselection ill f;ivo~.o[ ;tggi.cssio~~will IIC less 1.igol.011~. (:or II<.I.SIIIPANII (:~I~III.,\.~I~N.-~'J\,~I~L~-~wco~t~.tsllil)s, wliicll ~\rcret~ot sr;~gecl I)y the obsc~.ve~.s,\vcl.c obsc~~vctl,;untl Ilonc entletl ill c~ol~ul;ttio~~s. Sc.ve~.;llc.ol)t~l;trio~~s ~#vc~.c ol)sc~.vctl 1)etcvcen li/;t~.tlsill wllic.11 ;I letnalc selectetl 1'01. 11~1.t.eccl,tivity wits inirotlr~cctl by the obscr\jet. to ;I 1.csitlellt rrl;tlc. The c.orl~-tsl~il);111tl c.ol)e~l;ulion by (:olo~.;utlo li/;~l.tlsill ~hcl;~l)or;~to~.y was sttttlieel ill tlcc;uil I)y one ol' III~st~~tle~lts (I;crgt~soll, llI(i5) ;rntl tllc l~eltl;tntl 1abor;rtory 1~ell;tviot.;tl,l)e;t~.ctl iclc~ntic;~l ill c\,ery ~.csl)ccL.'1'11~ (:olor;rtlo liz;trcls clo less (i~.(,li~~gof t11c [~III;II~I~I;III tliose ill 'l.ex;ts, tlley 1ic.k tlie l'c~tr~;rlcsmore fre- (iuu~lly,colxrl;ulio~~ I;tsts 111utl1 longel. (;I ~lli~ll~tt:01- 11101.~) ;rtltI i~l~olve:,;I tlo/clt 01.nlo1.e lxlvic. tll~.ustscot~~l);r~.etl with l1;11[ th;rt IIIIII~IIC~ill 71'ex:~s. 'I'llc leni;~le1-ejec.ts the cottrtitlg 1n;tle by giving ;I sl~~rcltlcrbob that is silnil;tl. lo tllc ni;tlc cot~l.tsllil)l~ol). 71'l~is 1.ejcctiorl mech;t~lis~nsecltls quite cl['c(li\.c ill cluitkly t1isc.0111-agingtlrc 11i;tlc. 'I'lie rejectiotl nlec.lianis~~lin Terns t~su~lllyi~lvolves I-ccl.e;tt oC the fe~n;~le,but the nlale is not as readily tlisco~~r;~getlby this I~ehaviorant1 inay attenll)t courts hi^ sevei-;11 times. One of the ;11)1~11'aitlytlo~llin;~nt (2-yc;~t.-oltl) 111;i1es courtetl 2 dill'erent l'enl;~lcs,one ol' wlliel1 MYIS ;11so c.oi~~-te(l11)' ;I ye;~rling1r1;tle. 1;tcll oC two other I'e~u;~lesw;~s c.ou~,tctl by two tlifel-ent 111;tles.One tlo~riin;i~rtrn;~le per- I'ormctl I(i cot~rtsllil)~,or ;\I1 I)~IL(i 01' tl~ctotal number observed. l;.vcn \vitlio~~t:I lligl~lytc~.rito~.i:~l systc111 the ~I~III~I~;IIIL111:11e III:I~ e11,joy :I re111-o- dt~c.ti1.c ;~tl\r;~ntagc. k1o~11:I<,\NGI 'I'Al3I.E 5.1 So~t..(:o\II~,\H,YI.I\I: l)l\.lrh ON IIO~IC-R~\N(;ESI/I. 01;I.I/.\KIH IN C:OI.OK.\I)OANI) TFY.\Y, I)KI I:RM INI:II BY '~IIREEI)II+ICKI:N r MI. 1'1101)s All ligures arcs ill ;~cresIIIII'SS olli(~~wise~~otctl, ;~ntl all ale Inc.ans - ~~~ -~ -- ~-~~ - --- ~ ~ ~ I't.sas (:olol.;ltlo ------p~-~ ~- iVlctl1otl of l - ~ -- - -- ~ -- - ~------Kecal)tc~rc' .I I ,113 .O(i .I15 .Oli .02 Tracking .2 I .05 - .07 - .02 I'rolx~l)iliLy (1(\11si[y~IIIICI~~I~ .-I!) .I5 ... 97 .25 ..? 8 .O!l 1c11rI~I (f.) :17:1 20.4 2lj.li 27.1 34.7 18.8 ~- - -- ~ ---- ~ '1.i1ikle :111(l VVoocI;~rtl,l!)(i7, l~acl11ote(I I'ro111the 1965 clata in (hlor;~tlo that the rcca1)ttu.e r;lclii an(\ coml~i~tetlhome I.;t11ges for i~lales;~nd l'en~alcs were not sig~liflc;~~ltlytlillet,e~~t. However, tlle 19(i(i tl;~t:i tlo not i~lclic;~~e tliis. 71'l~e111i1les in l!)(i(i II;I(I sigt~ific:i~ltIy1:11.gc1. ~.ce;~l)Li~re radii ;111(l1;trgcr llo~llcixngcs bilsecl u11o11 rcc;tl)tu~.es;~utl t1.:1t king than did l'e~u;\les.71'llis is the first ~IISI;III(.Cin wllicll the 1.ecal)tul.c ~,;~tlit~sl':~iled LO give consiste~it i.est~lts,~)~~ol);~bly bec.;~use of ll~cshort-te~.~ll sttltly ill l!)(if (2 weeks) comlx~retl wit11 tllc long-term st~~clyi~r IO(i5. Never ill the 71'ex;~sl~olx~latiot~, in whit 11 the IIIC;III I.c(.;I~)~II~~r;~dit~s\V;IS 1101 i~~llue~~cetlI)y the time over ~vllichc;111- lures wcl-c 111;1tle,clicl tile pei.iotl of 1.ec;tI)tu1.es :tl~l)l'o;~c.llso sl1o1.t ;I ti111e ;IS two weeks. This nl;~ybe too shor~;L tinic to measure ;ic.c.~~~-;rtelythe move- Irlents, 1);11'tic.11lal.lyof tl~cless c.onsl~ic.lro~~sl'e~tl;~les. 1)~:11sitytlifi'c~~e~ic~es l)e~weet~ l<)(i3 ;IIICI l!)(i(i 1i1:1y iilso l)e i~lvolvctlin tile tlill'e~.cntcc ill I~on~e-i.;~rlgc\i/c, 1'01. t1lel.c wc~.t~17 resitlent t~i;tles ;111tl 18 l'em;tles in 1965 compa~-etlwit11 13 ant1 8, resl~ecti\,ely,in 1966. These differ- enccs, however, will not fully explain the results, lor fem;tles sliould have shown ;I 1;trger incrc;tse in 1nc;tn 1'ec;tl)Ltll'e r;ltliits th;tr~m;~les. I'm ;tfraitl tl~;rt nry (linkle ;t11(1 Wood;trd, IO(i7) st;tLenlelit ;tbottt the utility of the rec;tpture ~.;ttli~lsw;rs overly ol)timistit.. I still 1,clieve it is the best ;~\rail;tblemeasure ol' ~.cl;~tivctrlovcmcnts, bttt ;I longer periotl ol' time than I st~spectetlm;ty l)e 1Icc.ess;tl.y Locs~i~~i;ttc it ;kccul.;itcly. ~[OVF:WII~N-I.1:~onr .I.HE HAT(:IIIN(; S~~~:.-Esse~~tiitlly all yot~~~g ~~rotlucecl on t lie ;t~.c;tit1 ['.)(iswere 111al.kcc1,;tntl solne s~ll.vivetlto I)ec.ome study-;tre;l resitle~lrs ill I!)(;(;. 7'11~clistance hot11 the llatchiug site to the geometric c.etitcr of tlie Ilomc l,;lnge l'o~.tlte single I'emale irlvolvetl was 21 feet; lor 4 11l;tles it ;tve~.;tgetl1 I0 feet (67-13:)). The cl:tt;t ;tre too sc;tnt to ~il;~kcfruitl'ul c.otiil);t~.iso~iswit11 the Texits li~;trtls.I-low eve^., it w;~sclc;~~ t1i;tt movement 01' yo~~~ig.li/;t~.ds I';II. out of tl~cstt~cly ;tre;t w~ts;tt ;I IIIII~~higher frequency th;tr~in tllc 'l'cx;~s~,ol)l~l;ttio~r Tllcsc cl;tt;t will be 111.esentetl in the section on e~nigr;\tion. NAT~I.ITY.-~IIlO(i5, effort was 1r1;1tle to nl;trk all young protl~tceclin the areit. This was not con~l~letetlI)y :\i~gust,when the summer work was ter- ~rlin;~tecl,becallse all of the young llacl not hatchetl. 1 reu~l-net1to the area in October LO conll~lete~-egist~.:ttion ol' the young; no new lizarcls were beirig I'ou~tclon the ;I~C;Lwhen 1 left. The tot;tl nl~rnberof young procluced by the resitlent ;rtlults was ;~ssun~etlto be the number market1 between Jl~lyarltl October, vi~.,128 ((54 8 d ; (54 9 p ). Tlie ;~cttialnumber produced was only ;tbo~tt7 1)cr I'emale or what niight I)e expecletl from only two clutches of eggs, or tl~rceil many I'e~naleswere immature at the onset of the season. The ~lat;tlitywas lower than ever observetl in the 'Texas populatioll ever1 ;tftcr r;tdiation of the atlults. It is about one-hall tlte average in Texas O\ICI. scve~.;~lyears. l'o mnint;~in;I st;tble pop~~l:ttionsix, ;tssuming ;in nnnu;tl tlli.liovel. of ;rtlults, ;I[ 1c;tst two of the 7 young protluc.ecl must s~~rviveto nl;l~llrity.I);IL;I ;\re ;tv;tilable on both c~.ucle~no~.t;tlity of the yourig alltl on popi11;1tio11t~~~.no\~er ;1111otig the ;t(l~~lts. Sunv~vons~~rr~.-OI;t11 ol' the young markctl in 1'365, thirty-lour are knobvn to 11:1ve s~trvivetlto ;I ni;tlure size tlul.ing the l!)(i(i reprotltlctive season. Tllis figure ol 20 per ce~~ts~trvivorsl~ip ol ~OIII~~is only slightly higher tllan tl1;lt rcc.o~.tletlin Texas. However, tllere cloes ;tppe;tr to be a tlifl'el-ence in tile time ;tt wllicl~ no st niol-t;rlity occ,~t~.~,etl.Seventy-foul ol 128 young (58 1)el. cent) s~~~.vivetl;tt 1c;tst to 0c.tol)er. I'lie me;ttl age of the Co1or;ttlo lizards lvoulcl bc allout 10 weeks at t11t. ti~~~ethe ;t~.c;t was ~vorketlin October. Fig~1l.c I7 sllows t1i;tt ol~ly;~l)ortc Ira11 ;IS Inany of tl~e'l'cx;is young sul.\'ive to this age. -I'liel.eI'ol.e, tllc I);rctcrl1 of ;tg:-cspecific rnol.t;tlity is tliffercnt f'or tlic (:olol.;ttlo ;ttitl 1'ex;is li/;tl.tls. The winter 11io1.t;rlityis cviclently cl~titeliigll it1 Colol.;ttlo, 1'01. few ol tlic li/;rl.tls 11;tntlletl ill 0c.tober xve1.e rec.;ipettretl tl~c I'ollowi~~gs111.illg ;is ;ttl~ilts. 111 l!)(i5, lilty-ni~~e;ttlitlt li/;tl.tls wc~.c~n;il.ketl, ol wliicli 13 were recove~.etl it1 I!)(i(i, ;I c.1.rtcle ;ttlt~ltsitl.\,i\,o~.sl~il) ol 22 pel' tc~it~vllicli is higher by t~'vic.c ~II;III tl~c;iclt~lt SIII \.ivol.slril~ol)sr.~.vctl ill 7'ex;ts o\,c~-5 genc~.;ttio~is. IRIRII(;IO\-I.IONANI) l~:i\~~(;~~,\~~.~o~.-~l'lieS;IIIIC ;iss~~~~il~tio~ts ;tbo~t~illiliii- gr;irlts wcl.c ~l~;itlc;IS ill tlie 71'cx;~s])ol>t~l:ttion 01' !)Y young ~lr;rrkctlilisitlc (lie stt~tly;tl.e;i I~ortntlal.ies,I2 eliiigl.;itc(l (13 pel. cent). Of 33 ;i(lttlts ~narketlot~t- sitle tlir ;tl.c;t, .3 (!) pel. c,c~~t)iiio\~etl illto the ;tl.e;i ;IS I-esitletits.Sc\,en ol 21 (33 I)~I'ee111) ~.csiclc~~t;1cI111ts ill IO(i(i wel-c c.onsitlel.ctl i~il~~iig~.;i~~ts.71'lle~(sesri- 11i;ttcs ;II.~1101 grc;itly tlillc~.c~ltl'l.otlr tllose lor the 'l'ex;ts l)ol~iiI;ttion. 011c l';~(,t:II)OIIL e~~iig~.;ttioi~ ih ht~.iki~igly (lilfc~.e~~t in tl~c two l~ol>~tl;itio~~s. In the ~t111111ic1.01' l!)(i(i 1i.c ;tlte~iil)te(lto kill ;IS 111;11iy II~;IS;IS possiI)lc witlli~i 200 y;il.tls ol rhc stiitly ;II.(YI.111 tloi~tgso, we collec.tetl I0 tlist;tl~te~~iigt.;~~~ts I't.ol11 tlic st~~tly;tl.c;t, ;tllr~ost10 1x1. (,elit 01 tI~etot;tl yo~i~~g~n;t~.ketl tl~c 1)l.c- vioits yc;ii.. I<:iglit oC ~licI0 were ~il;tlcstli;~~ \vc~.c I)ctwec~l I07 iuitl (i!)O l'cct l't.ol11 tl~cil.1;tst ~~cco~.tlctll!)(i5 t;tptul.e poil~t(2 = 3(i(i feet). Fl'lic t\tio 1'cnl;tlcs ~vcrcl.ec.ol.tlctl I I0 ;tntl I!)O l'cet ;tw;ty 1'1.oi11their litst 1965 c.;tl)tttrc points. Not olll)~is tliis ;I high ])i.o])ol.tio~i01 cIiht:~llt e~~lig~-;,~~ts,but tlie tot;tI of 10 exc.ectls the toltrl 1111111Oc~r.01' siic.11 1o11gclist;incc llio\rc.lllents I-ecoi.tlctl 1'01. the rl'cx;~sli/;t~.tls o\,c~. ;I live-yc;tr ~)eriotl.l':iglrt of the 10 we1.e fi~.sr-yc;i~. ;ttlt~lts,~~ci~tIo~.ci~ig 111y (o~ite~itio~~ t11:tt tl~c g1c;itcl. o\,e~.Iitl)01' age t.l;isscs l'o~~es11io1.c. s~il~;ttIi~lt ;111i111;ils oi~t 01 tllc ])ol)ttl;i~io~i.11 111;iy \eel11 l);i~~:ttIoxi- (XI LO ;it t~.il)t~tethe tlc\,clol~~iic~~tol' soc.i;il I~ic!l.;~rtl~ics to ~.rtl~tc.ctl>tgg~.cssio~i a~~tl;lt rllc S;IIII~titile ;~tt~ib~~tc! gl.c:ttc~. c~iiig~.ittio~~ to tl~c ovc1.1;111 ;inti c.ol~sc~- cluutt c.onllic.t l)ct~'t~c~~li/;rl.tls ol tli llercn t ages. Sollie ;ttltlitio~~;rltliscttssion ol' tliis poil~tsecliis \tr;~i~~.;t~~trtI.111 -I'cx;is ;I li/;il.cl 11it1st1.cl11.otl11t.e tI~il.i~ig its lil.st rcl~ro(l~~cti\~csc;lsotl 01. (lie ~\~itl~otttissue. Illitler sttc.li co~itlitio~~ssclcc- tioti UJOIII(I I':I\JoI. st1.011g:tgg~,esbiot~. At t11c S;IIIIC tiliic 111cl.e ~'t~ottltl:I~I)(!;II. to l)c little :tcI\,;itlt;~g(>to ;I li/:t~.(l lc:tvi~~g;I t.c~.t;iil~ ;ire;t. 111 (~olor;t(lo,;I 11011- ;~gg~.cssii\~li/;tl.tl III;I~~.ctt~;tili sttl)lllissi\,c to ;I (lo~~~i~~;t~ito11e ill ;I so(.i;tl 1lie1.- ;~rcliy,I)ttr live to l)~.eccltIti~.i~~g its set.ot~(I 01. t11i1xI ~~cl)rotlt~cri\,e se;iso11. Ho1,~- c\,tXl.,l)y eliligl.;iti~~git 111iglit I)? :iI)lr. to l>~~~ccl(1111.iilg its 111,stS~LISOII ;tlso. Pct.lia11s tl~el.ris a gcrlc!tic. I):isis I'or (lie ~>lier~otyl)c01' "tlisl~c~~se~.".cvhic.l1 11;is ;I sclectivc ;~cl\.;~~~t;igeri~rtlc~- otlc tlc~~rog~.;tl)l~it~.cgi~lir, IIII~ 1101 ill ;inotllcl.. POI~III.~\~I.IONS~I.KII(:.I~IIRI~..-~~~I~ sex l.;ttio 01 j~iveliilcs ;i11c1 it(111lts \\';IS cssc~~ti;tlly50:50. 71'hc ~.;ilio1v;ts cx;~ctly 50:50 ;Iliionx tlic! yott~~g1il;irkctl ill l!)(i5. 01 the 59 atlrrlts h;tntlletl in I!)(i(i, thirty-two (5.1 pel. tent) were ~n;rles; ol 5:) 11;1ntlletl in l!)(i5, rlle same ~)rol~ortionwerc Sernales. Exc-lt~tlingatl~~lt 1ir;rrtls that 1vel.c market1 for the first time in I!l(i(i, ~llcrewere 4(i atlults of known age Il;rntlletl in tl~cI!)(i(i breetling season. Of these, IS (28 per tent) were Plltl-ye;~~.;~dlrlts. Of [he 21 strrtly area residents in I!)(i(i, 15 werc ol known agc :111t1 5 01 tllc 15 (33 pel- cent) wcre 2ntl-year ;~cl~~lts.In no yc;~rtlitl tllc 1)roportion 01 211tl yc~ur;~tlrrlts in the T'cxas pol)~~l;~- tion csc.cctl 1 1 1x1- t c11t. S'OI~I~I.ATIONDENSI.~Y ANI) S<~obi~ss.-Ti~~kle;111tl \4foot~~1;11-~1,lLI(j7, li;r\~ ;~lre;tcly~)rcsenletl tl:11;1 on thcsc ;rsl)cc ts of tllc (:olor:tclo l~ol~ulationin 1965. little can be :~tltletl to the inlo~.tl~;ttioll011 I)io111;tss, l~utsome ;~tldition;rl figures ot~tlcnsity are ;rvail;rble. Tllc <;olor;ttlo 1iz;trtls :tvcr;tge consit1e1-ably slrlallc~. than tllose in 717ex;~swit11 the result 11l;rt the avel.;rgc ;tdrrlt biomass is ;tbout 40 grirnls to the acre c.omp;~etlwit11 ;tl)ot~t50 in Texas. Howcvc~-,as I have 111-eviously l~ointcclout, thc tlensity of <;olor:~tlo1i~;rrtls is higher ill optin~um1iabit;tt; only ;rl)or~t50 I)er cent of thc sll~cly al.e;t in Coloratlo su11po1-ts ;I high tlensi~yof r1t;is. In l!)(i5, the tlensity in the (;oloratlo popt11;rtion ulas 17 I-csitlent ;~dl~lts 1)cr ;rc~'e,cornl~arctl wit11 an o\re~-;~llaverage in '1'ex:~s of bout 14. 111 I!)(i(i, tllc tlensity in tllc (;olo~.;tdopol~ul:rtion was cjuitc low ~lilllonly 21 resitlent 1ir:rrtls 01- ;I tlensity 01 :tl,otrt 10 IEI- ;rcl.e. I ]lave tlcterniinctl ~lletlensily ~rntl1)iom;iss in only one other ~~olmlation 01' [lltr, 111;tl being near Wlercury, Nevada, in thc summcr ol 19(ifl. Over ;I 1)criotl of (i wccks, 1)oll;rltl \i\rootl;~l-tlant1 I recol-tletl 29 rtt:rs on ;un itl.C;t sliglltly l;r~-gc~-th;tn rhose ~~sctlin Tcx;ts ;rntl Colo~-:tclo.I7lle tlensity here TV;IS ;I~OIICI2 Ijer ;rt.t.e ;rntl the 1)ioln;rss per ;rcre about 34 gl.anis. The Ne\iatla 1l;tbitat wits in very tlry tlcsert ant1 yet the tlerlsily reachetl by utas therc was not f;~r1)elow tli:rt rec.ortletl in Sal- nlorc 1)1-otl~rctivch;rbit;rts in other ~,;u-ts of its I.;III~C. I~IS(XISSI~N01.(;O~I~~~\I~~~TI\~P; I)PM~(;UI\I~IIY.-\~\'~~~~ o1i1y ;~I)o~rttwo-tllii-(Is rul.llovel. it1 irtlr~lts;tntl~~;rlly, ant1 wit11 :tl)otrt 80 per cent crrrtle mort;~lityol young, IIIC 1)o11ul;rtion si/e can 1)c lnaintainctl at a st;tble level with each 1'em;rlc ~)~.otltrcingonly 7 young per yc;ii', i.e., with about one-hall thc I-epro- tltlc.tivc ~-;rtc1.ecluil.et1 in 1'ex;ks. \l\~l~ctl~ct.the tlill'c~.cncesill the slruc.trr~.cand tlyn;r~nitsol tllcse ~)ojx~la- tio~~sII;I\T ;I genetic b;rsis is a clrlcsiion 111:t~ Inlrst be askctl by solneorlc inter- estetl in the evo1utiona1.y ;Ispects ol ecology. The answcr is that both are probably involvctl, but 1 think that the tlillel-ences in clie envil-onments ol the two :rl.cas are !)rim:~rily 1-esponsible lor the tlifel-cnc.es in tlcmogl-apliy. 71'hc s11o1.1c.r;rc.tivity sc;tson ;111tl lolv(.~-te~iil,:~-;rt~rres in (;olo~-;~tloma)- ~-es~~lt, intlircc-tly, in ;I 1)rolongctl lil e rxpec.t;rnc y ~,vllichleatls in tlil-n to ;rlterecl ;rge strlrc.tu~-c,;rlte~-ccl I)I-eetling stl-uctlrl-e, ant1 ~)osaibly;iltc~.rtl behavio~-. It 1lli211tbe s11Ifi(ie1ltI'I.~III the ccologic;rI 11oi11t 01 ~.ic~vto eti(l ~vitll11lc ol,se~.v;~tionthat the ~~lativelylow birth rate in the C:olor;rtlo li/artls bal;r~lces ;I rel;~tivelylow tleatll rate co~npiiretlwit11 that in Texas. No~~ever,thcse are sc.;~rcelyt;llrse ;~nclcftect rel;rt io~lsllil~s.The obser\~etltlilfcrences ill rcprotlr~c- ti1.c rates c;111 for an e\~olutio~l;u-yexplanation ~vliicli I sli~ill;itternpt to ~)~'ovicle. Flllec.lrtt(h si/e ill Colo~-;~tlois sn~;rller t1la11 ill FI'ex;~s.Rec.;~rrsc it is tlifli- (t~ltto visr~ali~es-lec ti011 lor a lower c-lrrtch si/e, l~rse, ;IIIO~~ICI. expliul;rtio~r of the tlif1t:rcnce must Ile so~~ght.I 1l;rve ;~l~-e;~tlypoi~ltetl o11t tll;~teven writ11 ;I srn;rlle~.si/c ;I[ 1r1;rtrrrity 11e;rl-ly olle-11;rIC ol the young 111-otluc-ctleac.11 ye;rl- ;iI-e itn~n;rt~r~-cI)y the onset ol' tile I-eprotlucti\,eseason in the Sollou~ingspring. 11' these li/;~~.tlsill (;olor;rtlo hat1 to re21cll 42 Irlrri, the ~nininlurnsi/e at ~ll;rtu~-ityill 1'ex;rs li/;r~-tls,tlrey might not ~.cl)t.ocl~rc.c;it ;111 tlltring their first season. 71'llc~.c.l'o~.c,1 tilink 111;lr selct tio~lhas ;rc-tctl to 1;rvor ;I sm;~llerside at ~rl;rtr~rityin tlle no~.tIic~-n1);tl.t 01' thc range. 1)cc-atlse this results it1 sm;~lle~- l'e111;11es,it ;~rrto~r~;rtic.;rlly1-csr11ts ill s~n;rller c.lr~tches,l'or it is ~,r;rctically rr~~ivers;rl;rriions li/;~~.tlsfol- tllrtc.11 si/c to I)c tlil-ectly ~.el;rtetlto body si~e withill the s;rllle s1)ec.ics. ;\I1 01' this ;rssulnes hat the tliffcrenc.c in botly size h;~s21 genetic basis ;~ntlth;rr the ~n;rtu~-atio~i;rt tliffet-cnt si~esin the t1'1~0 ~)ol)~rlations,likewise, is gcnctic;rlly tlcterminetl. Some srr1,pol.t 1'01- the 1;rtter. itlc;~c.olnea 1'1.orn o111. l,hotol~criotlexl)erilnents with the utas in which posi- tive responses were never o1jt;rinetl 1.1-on1Tex;rs 1iz;rl-tls untler any ~~hoto- pcriotl or tcllll~er:~trrl-eregime if tllc liL;r~.tlswere snl;illc~-than tlle minimrrm six ;~tnl;~trrrity. Nl~me~-or~scxperi~nents nectl to Ile tlonc. l'r;rnstc~-01' lizal-tls bc~weenthe t~roare;rs worrltl ;insurer some cjl~estions21s ~vorrlcl com~~arisonof the size ;I( rnntr~~-ityin '1'cx;rs ;rntl Colol-;~tloli/n~-(Is that were ~-;~isetlin <:olor;rdo ;rntl 71'~~il~,1.csl)e~ti~ely. '1-he 1';lc.t 1-cmai11s1lla1 if sclec.tio~lIl;ls fa\,oretl ;I s1r1;rller size ;it rn;rt~c~-ity it. has I-es~rltetlin ;I Iligl~errcl~rotllrc.tive rate t1r;rn woultl have bcen possible iC the six ;rt irlatrl~-itywere the same in the two ~)o~ulations.The 1101-tllwal-d tlistrihution of this species Inrlst I)e limited ;it those points where the re- ~j~-oductiverate is not sltflitiently high to prevent l)ol)~~lationIl~rctuations that occ-asion;rlly or 1-eg111a1.lygo to zero. It nligllt fairly be asketl m~lly the clutch side of 1'ex;rs 1i;rartls h;~snot irlc1.easctl I'l~rtlie~..T'hi s woulcl p1-cst11ll;1blynecessitate ;11i incl-ease in botly size or a recluction in egg si~ethat might be inimical to srlrvival. Tlie Former cll'ect woultl result, 111-esum;tbly in greater competition witli larger species. I\ I\ larger body si~elrligllt also tlelay the acliievernerlt oS sex~1;lli~iat~lrity ant1 l~esultin ;I lowered ~~cl)rocluctiverate. i\ i\ I-ccent htt~tly(McCoy ant1 Hotltlelibach, 19(i(i)on the clutch si~eof the li/;~t.tl C71rrt~itlo;b!~orlrstipis was lnatle in the same (;olorado ;uncl 'I'exas pol)t~l:~lionsin wliicli 1 stutlietl IJta. C:. tigris has larger and Sewer clutclies in C:olor;~clo tll;ir~ill 'l'cxas. Tliese cliffel-ellees are no1 ex1,licable on the basis of tlillei~e~icesir~ egg si~c01. I~otlysi~e in the two pol~t~latio~is.They conclude tliat tlic si~~gleI)rootlecl~iess irl C:olor~;~clois owing to the sliost growing season ;t~ltl;tbsellce of l'ootl l'or liz:u.ds einesging early Srolll hibernation, ant1 that tlic 1.,i~ges . . clut(.l1 si/e evolvetl as co~iil~ensi~tiorifor tlie cliniatically enfoi-ced sirigle b1.ootletlncss. \I\'li:ttever the cause of the sirigle broodedriess, there is no ~iccessityfor linking clt~tclisi~e witli that pl~eriolne~lon.1 would think tliat lasger cl~~tclicswoulcl be eclt~ally;~tlv;~ntageous in a rnulti-brootled popu- 1;1tio11.That the 11t;ls aricl the w1iil)tails have evolvetl opposite geographic trencls in clutc.ll six is clear, I~utI think tlie season Cor this is not relatetl cliscctly to tile ~~unil)e~.ol' c.lutc.lies l~rotl~~cetl. l'he tlemog~.aphyol l.el,tiles is still very poorly known. Tlie majority oC ~,~~blishedpapers on tlie st~l'jcct contain little irllor~natio~lof value. Corn- ~ricrlisin tlie 1iteratrlr.e on clutch size Ixlsecl on a very few intlivicluals, on movements, on g~.owtlr,;~ncl on longevity at-c of little interest because the C~;IL;I ;we too scant to make cornparisor~swit11 pol~~~lationsoT other species, or eve11 to clefinc tliosc asl)ec.ts of the 11opu1;ttions that were 1)~11-porte(lly me;tsurecl. 7.11~cluestion mt~stbe asked, why are any tltorough pol)ulation studies of v;~lt~e?This c;111be anstvesecl ;is follows: 1. They psovitle quantitati\~edata of v;lluc to tl~etlieorctical ecologist. 2. 7'1iey suggest 1"-obleins to tlie expel-i- ~ncrrt;ilistwliicli can I)e solvetl orlly by ~il;tnipulatirigl~ol~trlations in ilic Gelcl oi. 1;1l)oratosy.3. l'lney arc of interest to tlie evolutionary biologist becat~se tl~ey~~~'ovitlc tlata 011 sltch things ;IS l)ol~r~l:ttionsize, l~op~11;ttiotiCLI~IIOVC'I., bell;~vio~.:llch;i~-;~cte~.istics, ant1 t1cgr.e~ ol' i~io\~e~nentwhich infiueilce tllc cousse of evolr~t ion ;I[ [lie l~ol~~l:~tionlevel. As I tesll~in;~tc~liis st~~cly, 1 it111 still lclt a\lith ;I Seeling of tliss:~tisf;~ction; cles1,ite ;I we:~ltliof t1escril)tive i~lformation,the big p~.ol)lelrisstill rem,dl11 ' to be solvetl. However, I woultl riot 1i;ive been aware of some oS tlie~riwithout the I)ackgror~ntlol' tlie lorig-tesnl 1)ol)tll;ttiori stt~dy.Sorlle of the l~roblelns ~.el~t;ti~~i~~glor. ~vliicli 1 Iiol)e LO se;trch for a soliltion are as follows: I. \/Vll:~tregi~latcs the ])opr~l;ltiorrrluruhel-s 01' this species, and is the 1-egu- I;~toryr~icchanism tlilfct,ent in tlifferent parts of tlie range? 2. CVII;IL :Ire tlie atlaptive \.;~lt~esol die ol~sel-vet1tliferences in sexu;rl tli- tllorl)hisrn, ant1 I)ch;~vior;~lIxlttet.ns 01' [lie IIL;I~?MTlr;~t 1';tctors h;~veinfltl- encetl the ~.etluction01' sesu;tl dinlol~phislll in the nol.thern tttas? H;1\1e the s;rnrc l;ic.tol.s ~.est~ltc~lit1 soci;tl Ilier;~rclries or itre these sirnl~lyby- l)l.oclt~c.tsol tlill'crent~esit1 pol~~l;~tiotl;ige strtlc.t~trei 3. \'\Jll;~t:~(I\,;~trt:~ge ;tee~.ttcs to ~llo~iog;~~trot~s;~~ri~ir;~ls? \\/11;1t \vo111(1 lr:tl)l)et~ to I'crtility, n;~t;~lity,;rntl s~~r\,ivor.slril)untlrl. ;I systclli ol' I'ol.c.etl l)olyg;u~iy? \iVIr;~twot~ltl Ii;tl>l>cn il' the sex ~.;~tiowere t1r;tstic-;tlly ;~ltcretlill f;~votof lc111;1les? 4. \~\Jh;tt1);1t.t Ir;ts the tlillerencc in coexistent sl~ecicsIr;~tl on the ccology ;111cl evolution of t11c t~t;~sill clill'el.ent 11;tl.t~ of tlieil. ~.;~lrgc? 5. \~Vll;tt itlfluetrcc on ~)ol)~~l;~tiolitly~r;unics (.;III ;i(.t~r;illybe tle~nonstl.;~tecl th1.ouglr al~el.;ttiorrof tllc ~)ol>~tl;~tiolrage stl.t~ctul.e? I tlrirrk such clt~estiottscan I)e ;~trswc~.editr ;I re;rsotrable length of' time with ;I tlo~cnor r1iol.e cnclosetl ;iI.e;ls 01' al~out1 ;~c.t.ee;rclr, ill whic.11 bi-eetli~lg structt~~~c,l)rctl:~tor levels, tlerlsity, ;~ntlotlier f;rcto~.scot~ltl I)c r~l;ttlipt~latctlat the whinl oI' the i~rvestigator.Suclr st~~tliesare 1'e;tsible in ;I rapitlly Iwcctling species like 1tt;t ~vlrichis cl~titeiltrln~~ne to close obsei-v;~tionnrlcl tlisttrl.l);~nce ;untl ;~rrietr;~bleto 1i1l1or;ttot.yst~~clies. Most of the ec.ologic;~lant1 evolutio~t;~ry p~~ol)lelrist1i;rt ;IIT ilrll>ot.t;~tltesist irr ut:rs ;ltrtl most of them (.;in be i~r\,csti- gatecl ~)~~oviclctlst~it:~l)lc ficlcl :urtl lal)or;~toryS;~c.ilitics :II.~ ;~v;~il;~blc. Over ;~ntl;~bove tlic 1n;ljol- clues~iotrs~.;tisctl by this sttrtly of ~1t:ts thc1.e is ;I neetl 1'01. 11111cli111ore (l;~t;t,tlescril)live thol~ghit may IIC, on I-cl)tile 1)op~11;1tiotis.71'liis i~iI'ot~~ii:~tiotr~:III be oI~taitle(lir~ :I r.cl;~ti\lely sIrot,t 1it11e ~xovitlctl he 1~ol)lenlis 1)rolxrly ;~l>lxo;~clretl.:I11 jltveniles ;~licladt~lts irr selecte(1 popul;r tions IIILISL ljc rri;~t.ke(I,])r~clcr~:~bly l'or 211 1c;ist t~wge~ie~.;ttiotis, ;tllcl tlrcil. sl~~.vivorshil)clcte~~~rrinctl. I'lris opel.;~tiorl lone wo111tl p~.o\iitle 111ttc.ll 111o1.eLISC~III cl;~t;r t11;111 is (t~r~.e~itly;~v;til;~l)lc for 11iost 1.cptiIc po1)t11;1- lions. Iitr:~lly,1 \vo~tl([Iikc to errrpI~;isi/et11;1t I tljilik :I( the terr~lilr;~tio~~ol lllis lellgtliy stt~tlyth;~~ Itlore m;ry be g;tinetl I)y ~rr;lnil,t~l;ttiol~of ficltl po1)11- I;ttiolls ol li~;il.tls tllan wet. be g;ti~retlI)y post I';~c.torc;~solring l't.o~rl c\esC1.il>ti\,ctl;~t;~. Ncvertll.:less, I feel th;~~the strlclies of most rcl~tilepol)ul:~- tiolis Ii;~\,esinil'ly 1101 ~)l.ogl.ease(lto tlre poillt where st1el1 ;in ;~l>l)ro;~c.lris I)Osil)le. Sue11 ~.el;~tivelysimple m;tttet.s ;IS t.el)t,ocl~~c.tivcr;rte ;irltl tlelrsity lllltler tr;~t~~r;rlco~rclitiolrs ;Ire still t~nklrownSol. tlie v;tst ~rl;~jol,ityol sl)ccics. Nca1.1y 13,000 captures of more tllan 3700 IJtn sttr~isb~lria~~clwere conl- piletl over a six-year periotl in popt~lationso1 this lizartl in Texas, Color;~tlo, ant1 Ncv;~tl;~,generally on study :u.e;ls j~~stovel. 2 acres in extent. The most intensive stutly w;~sol the populations in weste1.n l'exas wllcrc the purpose was to clr~;tntil'y;IS inany aspects of the l)olx~l;ttionecology of this species ;IS 1)ossil)le, ;t~lcl to use such inSornl;~tiott as ;I basis oS l~retlictingwhat tlill'crcnces in the biology ol' the sllecies wo111il exis1 in other parts ol' its range. In 'l'cxas, ut;ts 1;1y trt locrsl tllret cll~tcl~esol' .I eggs e21cli coirilx~~.edwit11 ;r ~nitxin~r~nl01' tlirec, oS 3 eggs eacll, in (:olor:ttlo. 111 1)otli populations, clutc.l~esare 1i11,gerin larger l'em;tles :ultl l:~r.ger c;u.ly in the season than 1;tte. '1'11~t1ilfercnc.e in clutcli si~c11as ~)resui~~;~ljlycolnc about by selection of it s~i~;tllersi/e ;I[ matrn-ity in tlic (:olo~-;~tlo],oljul;~tions. 'I'hc onset oS ~~cl,rotlrlctionin the Texas ~jol,~~latio~~s11;~sbeen sliow~l in the l;tl,o~.;~tol.yto bc 1)rought aljot~tl)~.iln;t~.ily by 11igl1 tenll)erattIres, r;~tl~erLII~III Ijy lengtl~enctll)liotol)e~.iocls. I;r~~.tllcr, the li~;~~-clsare protectetl in 'l'ex;~s;tgainst ~~nsc;lsonalrel,rotlr~c.tiort by ;I 1,criotl ill late I'l~llant1 c;~rly winter wl~cnll~ey arc ~~~~~~~~~~y to those I':tctoi,s tl~ato~.clin;l~-ily i1iiti;tte the esll.orls c.yclc. 'I'lle tlevclol)n~entol' the hrst c.lr1tc.11 ol' eggs in tlic spri~~g1l;is I~ecll slio~vncx~~c~~i~~~e~~t~~lly to tlcpe11t1 11rini:t1.ily r11)on r~tili~ation01' the lipit1 1.escl.vc storetl tlt~rinxthe l'z111 in the co1.1)ol.aatlil~os:~ of the l'crnales. I!,otll tl~ctime oS initi;ttior~of breetling ant1 tl~csix 01' tllc clutch v;~ry I'roln year to year. l'he first is vai-ial~lebecat~se ol' va~.iatioiisin teliiper;~tul-c ;11ii1 s~~nligl~tin tllc s~~rings01 clilferent yca~.s.l'lie tlillercnces in clt~tclisi/c ;Ire ;tssoc i;rtctl with tliI1c1ences in six stl-r~c.tr~rcol' the ]jol)r~l;~tio~lsill tliflcrcrlt years. 7'hc tin~c~.cc]r~i~-etl lo^. ;I l'cl~~;tlcto ~)~.oclr~c.e;I clr11(.11 ol eggs may v;lry l'~.onl;IS little ;IS 11 weeks to as long as (5-7, ;rntl is gencr;tlly longcr c;trly ill tllc ~.el)~.otlt~c.tivc'season. About two n~ontl~s;t~.c ~-cqt~i~.ecI for tlie egg to 11;1ccll ;rl'tcr it is 1;1itl, I~otl~in the Lieltl ant1 in the 1;tboratory. T'he itlean weigl~tol' ;In egg at tleposition is bout .25 g1.;1111;:r whole c1utcI1 01' eggs nay cotlstitr~tc25-30 Ijel' c.ent ol' tl~cbotly weigl~tol' :I g~.;~vitlf'e~rl;tlc. Over ;t 1)eriotl ol' (i surnnlel.s, Il;ttclilir~gs first :tl)l,e;r~.etL in the 'l'cxas lml)t~l;~tionbetween ,J~rnc17 ii~ltl23; in (:olor;~tlo, they hatch one 111ont11 1;lter. H:ttc.l~lingsin Texas I1;tve been 1.ecol.tletl l'l.o~rl,June to Octobel.. T'lle prol~ortionol' these s~rr\~i\~ingto ri~atr~~-ity is ;tho~~t the s;tlne ;IS the l)rol,or- tion ltatc.hing ;IL each pe~.iocloS the reljrotluctivc seitson. I,, S~)C~IIIsto~.ctl ill female LI~;ISin sl,cci;ll ovitluc;~l~-c!ccl)t:~c.les a1.c (.;~p;~ble of l'~.~.tili/ingeggs fo~;I[ 1e;tsl 81 tl;tys ;~I'tel.isol:ilio~~ ol' ;I Se~u;llc1rorrl ln;rle;: 1-l:itc.liling utas gl.ow ;it the rate of ;iboi~t0.2 per clay h-on1 Jline to Sel)teuibcr ant1 at ;il,our Iiall this rate in October and November. Ral~itl growth conrinues, ~tsu;illy, until sextiill m;iturity is resichetl, on the average abot~t/1 ~r~onrhsal'ter h;itchit~g,;111tl ;~lmost;~lw;iys within 8 n~oaths.(;rowtli of ;ltlults is ;ilmost negligible ;iftet. sexuiil ~~lntilrity. 1)urilig e;irly growtll LI~~ISslletl their skin at about 3-week interv;ils. 111 tlic f;rll sltetltli~~goccurs ;it 5-(i-week i~~terv;tlsant1 ceases tluring the winter. Ihu-ing the breecli~~gse;lsorl, ;icIi~ltsslietl ;it i~itervalsof 4-8 weeks. 111 tllc first week of life, incl.e;~sein xveigl~tis negligible. After this utiis inc.1.e;ise I'l,oln ;I lrlealr weight of 0.3 g~.:lrnsto ;tbout 1 gram within YO tliiys, to ;il)ot~t2 g~.:i~nsin 50 tl;~ys.The greatest weights ;ire ;~ttainetlby ntl~tltsin the slx'i~lg;sonic loss of weight occurs d~lringthe breetling se;ison. 'I'lie tails of j11ve11;tlut:is elorlg;ite al~outtwice :is fast as the botly, i.e., ;it ;t t.;ite of ;tboi~t0.5 111111 11~1.(l;~y. If the tail is ~I.O~CII,the rate oC growth ol' the ~.em;iini~igbitse is :tlw;iys less t11;in the rate of the intact tail. Because l.egene~.;~tio~~occ~11.s ;it the s;inie Ixte ;is the gi.owtli ol ;II~~11ibroke11 tail, ;I brokcl~tail ;tc.t~lallygrows fitste~tl1;111 ;III 1111l>roke11011~. iibo~~t10 per cent of j~~ve~~iles;t~ltl30 per c.ent of ;itlults s;in~pledou~sitle tllc stutly arekt Ilad broken tails. Little rege~~eratiorloccurs the first 10 (lays I'ollowir~g;I break, du~.ingwllic.ll tinle ;I c;~lloi~sforrris. Kegenerati011 of tails broken near the Ixise is ~ntrchI';ister th;tri those broken distally; the reverse is tt.tie of the gl.owtli rate of' the ~~nb~.okc~~base. There is little tlifl'erence ill tllc r;rtes of tail rcge~lerationbetween juveniles ;irltl ;itlults, but in ;tdults tllc grotvtl~of the ~~nbrokcnbiise is negligible. 011 the stiitly at-eas, 21s ninny ;is /I breaks Ii;~vebeen i~~curretlby ;I single intlivitlual ant1 ;it least 1 break is tlie ;iverage; fewer tl1i111 o11e-thil.tl of' the ;~tIl~lts011 the st~ltly;weas re;iclreil ln;it~~l.itya\~ithout losing ;I tail ;it least once. Lltiis ;II.C oppo~-t~r~~isticir~scctivo~.es; they feet1 thro~~gho~~t the yeill, wl~er~e\rertelrlpel-;itlll.es arc lligll ellough for them to be active. Ants ;111(1 SIII:III beetles comprise 50 per cent of tllc tliet by volume; the total voli~nle ol l'ootl e;tten per day is ~)~~ol);rblyabout 0.2 griirn. Six spec.ies of snakes ;inti 3 of' li/:~rcls are known ~,retl;tcors on ut;is, b~t tl~elxol~ortioti l;illing prey to these animals is unknown. Miinter kill, niostly ;~ttril)~~tal)lcto snowfall, ni;iy be :IS Iiigh :IS 25 per cent. R/l;iles ;II-e Inore often victirns t11;tri lelnalcs. Al~out3 per cent of tile inort;~lityto 11t;ls tll~ri~lg tliesc stt~tlicswas ;tttribut;ible to the it~vcstigiitorsthernsclvcs. i\bnor~nalitiesare rare i ti 11t;is ant1 were riot incre;tsc(l by ~.;itli;ition of the li/arcls. Injr~riesare inore common ant1 LIL;IS li;i\le been obser\letl to I.eco\,cl- fro111 even such serious ones ;is loss of' :111 eye 01-;I limb. iibout 3 pel. of the lirartls h;indletl it1 this study showed cvidrnce of some ;ibriol.- lllality or l~revio~~sitij~iry. than in Colorado. Hoth sexes perform ~)usl~-upbeh:i\lior, even in the ;il,sence of otl~erli7;11.~ls, LLI~ the function of this is tinknown. During ;~ggrcssivctlisplays tlie b;lc.k is st~.orlglyarc.llecl ant1 tlie bocly conlpressetl :~ntl tilteel ;IL ;In angle tow;trtl tlie ;~tl\iers;~ry.During rn;ttirtg tlie inale al.c.hes his back, tit-cles the Senl;~le,licks her, ;In([, if not rejected, ;rtte~n]jtsc.opulation. The clctails of mating alitl copulittion 1)roccclurcs ;ire clilferent in the Texas ;itit1 (:olol.;~tlo populations. l'lle aggressiveriess by li~;l~.tlsof both sexes it1 Texas Ic;~tlslo ;I sort oL cltt;~si-nloriog;urly.I11 tlic (:olo~.:~(lopol~ulation the ~.ccl~~cecl;~gg~.cssive~less cvitlelltly resttlts itt ;I social 1iic1;~rc.hy in wllich the oltler ;~dttlts~11.c clonlin;~ltt ovel. tlie ye;u-ling :ttlults. /\ggrcssio~l is not liltiitetl to llic ;1d~11tttt;~s, 1)ut beconies cli~itestrong ill the juveniles wlien they ;ire ;~bo[ttone-h;~lf gl.0~11; ~~i~csu~r~;~bly it rcs~tlts ill g~.catei-inovenlent by chen~. In the 1:tboratory the I)ehavior of' IILIS is sli;t~,l)ly:tlterecl. Aggression l)ccon~cs~.ctl~~cccl and co111.ts1iil~~~r;tctic;~lly ceases. Inst;~nccsof homosexual ~natings,Iievcr observetl it1 ~liclieltl, ;tre l';ti~.lyl'reque~ir. Tlic tl;~ily lile ol' the IIL:IS is otic ol' baskirlg irl uiol.nitlg ;~uitle\~ening wit11 irltc~.~ilittentleecling. I)ttl.il~g~lliclcl:~y they retl-e:lt bcneatli the sltacle of pl;~ntsor ~.ocks,but alrliost ncvcr r~ntlel.gt.o~lllclcxtepr in wi~iter.f\etivity begins sl~orlly alter sunrise ;tntl coriti~i[resiuitil tl:u-k, wl~cnthe li/artls b111.row illto s;~litl.7'1~ s;mle activity ~);ltrel-nc.ontillues tIl~.ougho~itthe yc;~r, I)LI~ is slro~~tc~~etlcltr~.ing c.oltlc~. ~~eriotls. It is also shol.rer in the C:olor;~clo li~ardsin t11c tto~.~he;~stcrnpart ol the range of the sl)cc.ies. 'l'l~esix of home I.;lltge ol' ttt;rs h;~sI)ce~l esri~nareel in tllrce w;rys. 71'llesc estimates v;wy l'~.orii.10 to .1!) ;tc.i-e in ;~tlultni;tles ;~nclfro111 .0S to .15 in ;itl~tltSem;~lcs in Texas. (:onil);~r:ible cstinlatcs in (:olo~.;~tlo;ire fro~ll.06 to .38 in m;~les;mtl .02 to .23 it1 ;~clultlcni:~les. Thel-e was tio col-rel;itior~be- tween the cstinlatccl ho~i~e-r;tngcsire ;~ntlthe riltrnbe~.oS c.;~l)tul-cson wllich tlie eslimate was b;lsr:cl. Tltc home r;lngc ol' j~tven;~l11t;ls less than 35 rrllrl sllout-vent lengtll was orily .003 ;lcrc (130 scluare Sect). The 1nc;ln ~-ec;~l,tun-e 1.atli~tswits lountl to be the tiiost c.onst;lnt ~)icr;tmelel.rtsel'ul l'or c.olnlxli-ing tlcgl-ee of movelnent, IILI~it is inlluencetl by clerisity z~nclto some extent by tlie cltn-;~lionof tirile o\.el. whic.ll capt~t~.cs;ire triacle. -1'11~mean I-atlir~s~1;is ;1bo11t 37 feet for ;tdult nl;~les;uitl 20 lor ;~cI~tltfcirl;~les in '1'ex;ts. Siiliilar figures wcl.o obt;~ineclSol. (:olo~.;tclo liz~~rcls.'l'hc avenge tlistanc.e between ~;I~ILII~~SW;IS51 Sect in ;~cl~tlt~rl:~lcs, 27 iri Seliiales; it MGIS less than 15 feet for you~~gli/al.tls ol botl~sexes. i\l'tcl. li;~tcl~ir~g,ut;rs gencl.;~llytlisl)el.sc xrcl-y little, the aver;Igc being otlly 11 l'cec ill yottng li~;~rcls,(3-70 it1 acl~ilt~nales, ;111cl 40-50 in ;rtlttlt I'enl;tles. 'l'llc tlistantc Iron1 the h;ttching site to the geonlet1.i~c.entet. ol the ;ttlult Ilolllc I-angc a\ze~.;tgctl8.1 Seet in males, 53 in fcm;lles. Ilt;rs ;Ire srrongly I~eliothe~.rnic;inti 1n:tint;tin ;I body telnljcratl1l.e near ::(i-SS" (: tl111.ingtllr SLIIIIIIICI. by bel~a\lior;~ltllel-moregr~lation. 7'he ~jeriod ol II~;IX~III~~II;~cli\:it)! 01' the t~t;tsin summel. col-rcsl)on(ls closely with those tirncs ol' tl~etl;ty when tllr ;urlbient telnl,el.;ltul-es are in the above range. 'l'llc (~.itic.;~ltllcrnl;tl ~r~;txi~nt~tnwas ;tbout 4.Y0C:, ;11ltl or~ly;I~IOIIL 50 scconds itre rccl~tit.c.tllol. ;~dttltli/;~t.tls ro re;tch this thc~.rn;tlpoint in tllc opct~on ;I c.lc;t~.(lay in sunlrnel.. '1'11~~~;~t;tliry it1 the 1'cx;ts l)ol~~tl;ttionsis high, ;tljo~~c15 young per I'et~l;tl(. ye;^^. oti tlle ;t\,el.;tgc. Su~.vivorsl~il)ol' the 11;ttchlings to mat~~rity is ~.;tl.cly;tl)ove 20 pet' cent ;t11(1 is so11lewh;tt Iligher in fe~n;tlesthan in lnales. 'I'l~ccttt.~lovct. in 1.esitlent ;~tlttltsis ;tl~ottl!)O l)er cent pel. ye;n- co~nparetl wit11 (i0-'70 1)c1. C.C'III ill (:olo~.;t(lowhere the ~.el)rotl~~ctive1,;Ite 01' the li7nrcl i\ ;11)ot11 11;111' t11;tc ol)\ervetl in Tcx;ts. .l'he n~;txi~nu~nlongevity obser\,ccl iot. ;III) 'I'C~X;ISut;t ;t(~t~:tlIyn1:trkecI at ll;ttcl~ingW;IS I00 tvceks, but tlie ;~\~ct-;~gc.lilt csl)cc.t:tncy ;it I)i~.tl~is only ;tljottt I!) weeks. 011ly one liz;~rtl w;ts I~;ttttllctltlut.ing this sttttly tl~tt11;1cl st~l.vivctlI'or tllree ye;tl,s. I':n~igt.;~tio~~;III(I in~nlig~.;ttion by JIIV~II~I~Swere low in 11otl1 1'ex;rs ;~ntl (:olot.;ttlo ~)ol)ltl;~tiot~s,l)t'olj;tl)ly tlot c.xc.ec(ling 20 1)er c.etlt it1 ;III~ycitr. I~n~~lig~.;trio~lII~;ttlults \\l;ts I~igllcr,l)ossil~ly ;IS high ;IS .I0 1x1, c,ct~~in the 71't~x;~s1)o1)1tl;t~io1ls. Kcc.ot.tls ol' lotlg-tlist;t~~c-enlovernetlts by ettligl.;tt~tsl'rotn rlte sttttly ;II.C>;~c.on~pl.isc.tl otlly 0.2 per tctit ol' a11 li~;~~.tls111;trketl ill the 'l'c.~;~~)ol)ttl;tt ion, but ;~l)lx.o;t(~l~etl10 ])el. c.crlt ill tl~c(:olo~.;~tlo j>olx~l;ttio~~ wl1c.1-c the g1.c;ttel- o\~c~.l;tl)ol' ;tge c.l;tsses 111;ty f01.c~g~.c;tte~. cmigr;ttion tIlt~o11g11(.otnl)r~itivc i~~te~.:tctiot~s of the yc:~~.lit~g;ttIl~lts wit11 t11c s~~~.vivitlg ;t(Ittlrs I'I.OIII 111c l)~.c.viot~sgtx~~e~~;~tiot~. 111 r17ex:~s, ~)~~~t(~tic;tlIy t11e e11~i1.e breetl- itlg ~)ol)t~l;ttiot~is c.o~~rl)owtl ol' ;trlinl;tls hatc.11etl tl~e1j1,etetling sunllrlet,, nni- ~n;tlsless rl1;111 ;L yc;tt. oltl, wllere;~sin (:olo~.;ttlo ;ibo~ttot~e-third of tlte I)~.cctlitrg1)o1)11l;ttio11 is 11vo ye;~t-sof ;tgc. I'ol)~tl;ttio~~tlcnsity v;ll-ies f'ro111ye;rl. to ye;il., but not 1llol.e t11:l11 ;I I;tc.ro~. ol' rwo. 'l'l~c;lvcr;tgc ;ttlt~lttlensity it1 the 'l'ex;~s~>olj~~l;ttion Mras allout 14 ~~csi(lc~~~;t(It111s1x1, :I(.I,~,1)111 this tk!(~lit~e(lto :I~OLIL6 in AII~IISLne;lr tile cntl 01' the t~cl)l.otlt~c.tivcse;tsotl. The tlensity 01' i~~vc~~ilesreac.11etl ;I Iligh of ;tbot~c85 1)c1';tc.l.e in July. l'he I)iom;~ss~~el)rcscntetl by these figures ;tvel.;tges 8.1 gl.atl1s l)ct. ;tcle. 111 (:olo~.;~tlo,the tlet~sityin two brectling sc;tsons v;lrietl Il.onl 10 10 17 ;ttlttlr resitlet~tspel' itere wit11 average biom;tss oS ;t(l~~lts(40 gtns l)c~.;I(.IY) less I~I;IIIit1 'l'ex;ts bec~t~~scol the snl;~llsi~e of tl~c<;olo~-;~~l~ li~;t~.(ls. '1'11~ cllcc.~soS l.;~tli;rtion ;ttln~it~ist(~~~e~Iin two dillcret~tye;u-s LO tile I.csi(lctlt ;~(III~I.;it1 I'cs;ts I\J~~I.~~lotetl ill ;I d~.;tstic,l';t11 in n;~t;tliry;tntI s~ll>~e- quell1 lower tlensity of rcsitlc~~t;~tlults the following ye;tl-. 1ntli1.cc.t elleels on rnovemcnts ;tntl growth tliro~rgl~the cllct t on tlcnsily wc~.os~rsl)cc.tctl, 1,111 not 11rovable fro111 rl~e;r\~;iil;tble cl;rta. Expcri~ncntal;111;11ysis will be rccl~~irctlto nnswcl. the cj~~cstions~.;~isctl by Illis study conc.e~-ningthe ~.cgr~l;~tio~iof n~r~nbcl.s, the J'tll~ctio~l01' tliIl'c~.- enccs in breetling strtrclt11.c, ant1 in bch;t\~io~.of the spec-ies in tlill'cl-cnt 1~1rts01 its range. For strcli st~itliescnclosctl ~)op~~l;ttionsin whit li \,;~~-i;tl)lcs citn be ~~~:~r~ipul;~tc(Iwill be 1.et111irecI. 'T'lie literatl~rcon 1i~;u-tlbiology, whic.11 11;ts 11ce11~.c\,icwetl tl~~-ot~glio~~t this repol-t, is ~);tir~fullyin;~tlcclu;ttc. bI11c.11 11io1-c in~cnsi\scs~trtlics of ;tt 1e;ist lwo generations in the lile 01' the li/;t~-tlsseen1 rcclr~i~-ctlto I)~.o;~tlci~the 11;lse 01' I;rctlr;rl kriowlctlge conccrnil~gtlie tlcn~og~.;tl)Iiy01' 1i~;rl-tl~~ol)rrl;ttiol~s. The clemogl-;~l)llice~i\~irorilnenl is exll-eri~elyilnl)o~.t;~nt ;IS ;I m;~jo~.~(IIII- ponent ol the total environment in whicli the selection ol alternate l~heno- types occ.urs in n;~tui-all>ol)~~lations. To ;rll st~~(le~its,too ~it~nicrt)~~sto ~ile~ltio~l, tli;~~ II;IV~ ]);~~.ti(.i]);rtc(/at some time in so~ncaspect ol this stutly, I wisll to cxl)ress 111y :rl>pl-cc-i:~tion not only lor their l~liysicaleffol-t, but 1'01- nl;lliy tlis(~~~ssions;111(1 itle;~s, so~rlc of whic.11 they nlay recog~~i~eill these Ixlges. Don R/IcGrcgor, 1)on Wootlartl, (;el.;i~-tlI-lotltlc~~b;~th, ,J;IIIICS 1'1;11/ ;inti Nornl;~n\I\'illi:~ms nlrlsl bc singlet1 out for tlieir clc(1ic;ttion to tlie fieltl 1~ogritrnu11tle1- living ant1 working co~ltlitions tllat wot~ltl,ant1 tlitl, tlis- cour;~gcotlier i~itli\,itl~~als.For tlieil- l;~bori~to~.ywol-k OII \,;~riot~s;~sl)cccs 01' the reseal-ch on (Jl(r, I wish to thank Sulrilic~-Dali;~, (;;II-I-~ I 1'1-i~iccto~i,N.J. llAl 1062 P~-clilnin;~~-yre~nal-ks upol~ tl~c ~oogcogl-;rpliy of Ii7;11tls inlial~itingll~e (;lc;rt 1%.1si11of tl~cI\.~.S~CI-II ll~~itetl States. \'\';~s~ila~i~~Jour. Iliol., 20:253-287. I IFF AND IIEMOGRAPHY or UTA 175 U,\KTHOLORIE\V,G. A,, JR. 1950. Tl~celfeels of artificially co11t1-ollecl temperatures and (lay Icl~gtlr on gonatlal tle\clol,lncnt in ;I lirartl Sarllr~siovigi1i.c. .Anal. Kec., 10(i:,19-(i0. 1953 'l'hc motlilic;~tioll l,y tempcratrlre of tl~cl~l~oroperiodic ~ontrol of goll;~tlalcIe\'el- ~~II~CIILill tile lira~dSrr~rLr~sio uigilis. Copeia, 19-50. ~%ARWICK,I<. 1:. 1959 1,ifc histo~yof the tomlnoll Nc\v %t.;ilantl skink I.eioloi~icrrrcr zr2lnirrlito. Tral~s. Koy. Soc. N. Z.,H(i:J31-380. R,\U\\~I~:K,K. I-., .ANII (:. BKI.\N~ 1966 I'hysiological ;inti I)iocl~e~nicalasperts of Iiiljeunation in tile stincid lirard Egcr- rricr cirr~rrirrglc~rr~ti(Gray, 1832). Pl~ysiol.Zool., 39:l-20. ~~EI.I.IS,E. 1). 196-1 A SII~~III~I-six-lined racerrrnner (C~tcrrritloi~lcor-11s,\c\-lirrrcrlrcc) pol>r~l;itiot~ill South Carolina. IIcrpctologic;~,20:0-16. l',l.,~11R, IV. 1. 19li0 'Slle ~rrls~yli7.;ir(l. .\ po1111lation study. [Jlliv. T'exas 1'1-chs, ;\usti~r l~osrlc,1). I.. I!)66 A 1)rclimi11;11-yrepol-t of rcp1.t)~It1~tio11in tlie teiitl lirasd, Crrc~rr~it/of)lrr~~-~r.r/r)rflcl-)'- /lo-rr., 11c.lrli1rgi.tlerljctologica, 22:81-!lo. novn, hl. M. hi. 1!t10 Tllc st~.rrc~~rrcof tht. ovary ;cntl ~hrfor~~iatiol~ of III? corpus Ir~t?r~rnin Huplo- (/rrr.l~lrr.~rrrrrr.rrlc~trr.\ Gr;~y. ()r~a~-1. Jonl-. hlicl-os. Sci., 82:337-375. UR:\Irsrnonr, I<. M. 53 The ;c~~~l~l~il)ia~~s;III(I~-cptilcs 11-0111 R;II~CIIO 1.;~ Urea. 'l't;~ns.S;II~ 1)irgo Soc. Nat. Hist., 1 1 :3(B-302. I~KECKINKIL)(;E,W. J. 1943 l'he life history of tlie I~lack-l)at~tletlskink, I:'icrr~c~ce.rse~~lc?ltriorrtrli~ (I3ai1-d). Amcr. hlitll. Nat., 29:591-GO(;. RROWN,E, li. 195G Nests ;untl yorltlg ol the six-li~lctlI-~~~I-IIIIII~~ Crrc~rr~icIo(~lror~rs sc~uli~icnlirs Lin- ncarls. Jor~r.Elisl~a blitc-l~cll Sti. Soc., 72:30--40. cha~nclco~rsit1 captivity. C:opci;~.70 1--7Oli. 196.1 Egg I;~yingand incul~;rlionof tl~cstrilxtl 1no1111t;lin1i~;rrd ~/10/id0~)0~lll ~r~~)itLill~~l~ (Tciitlac) wit11 ~iotcson ;In inc~tlx~tor.Brit. ,Joris. Help., 3:163-161. 1965 Ol)scrv;~tionsoti the life history ;rlltl I~cll;~viorof C/1r1111eleo/ro/r?rrli Stei~~d;~chncr. Copeia, 401-409. 1966 Observations 011 tl~clife I~istory;~lrtl I)cli;i\.ior of Cltcrr~releo l~ilrrc~rrint~rsFischcr. I-Ierpctologica, 22: 13-23. I~IJsI~\KI),TI., ANT) R. IIU(:IIFS 6 Gckkonicl li/;~rtls:avcr;igc ages tlcrivcd fro111 ail loss data. Scicncc, 153:1670-1671. < :nc:r.e, 1:. I<. 1946~A lirarcl population on 'l'inian. Copcia, 4-9. 191(ib Tail loss and rcgcncratiolr in a Pacific island gccko. (:opeia, 45 1948 A populatio~lof Carolina anolc. Nnt. Hist. htisc., 15: 1-5. ]!I50 Notes on Holbrookirc texa17n in Texas. Copei;~,230. 19591) A ~~ol,ula~ionof the six-li~ictlt-;~terun~rcr ((~~~r~~ri(lol~lro~-r~.\ .\(~\liriecrt~i.s).Herpe- rologici~,I5:Sl-Sli. l!)(iO(t l'avti~rition ;111tl l)clra\io~;it I)iv111 of Yaruo\\r's spill) li~;irtl~S(1~10~10r11.\ jc~r~owi. H(:l.pctologic;i, 16: 137. l!)(iOO I I!l(iI Ol):crv;itio~r\ 011 [lie I~iolog\oS ll~cli/;~~-):l :IR(IIII(I (~g(itrr(rill <;I~;II~;I. 1'1-oc. Zoo1. Soc. 1.o11tlo11,1~1:1:121-132. I I '1'11~ ~~ol)~ilalio~~co~i.;c~ll~entcs of life Iiistot-y plic~~omcn;~.()11;11 t. He\. Iliol., 29: ! o:i-I 37. 1!)1 1 .\ l)rclill~il~;~~.!SIII(I\. of the tl~c~~rt;il~eclr~i~ctticn~s oS tl(,scrt reptile.;. 1<1111.Amcr. MIIS.Nnt. Hi\(.. 83:ZiI20li. l!)(i5 I'.llcc.ts of S-~ratliationolr tlic tcstcs of tile lizard, litti sfonsb~~rianastc'jnrgeri. Int. jol~r.R;~tl. niol., D:(ii-SO. I960 Guou tli and c)rlir I)el~;~vio~-of the \Vest Afric;~~~lirm-tl ilgarrrcr ngo~~tnaft-irn~ro. Copei;~,9-4-96, I)~K~\'sKY.I. 1957 Sc;~son;~lchanges of fat bodies and gonatls in some lizards of the Arax river v;~llcyill Armenia. Zoologirliesi~~i%Iir~rt~;rl, 39:1209-1218. ~)l~t~1~11~\1<1)1',\v, (;, I<)(i(i !\ lnctllotl or co~ltltitigsotnc tlitwllal grouncl lir;lrtls of the gcncl-;I Holbrookitr ;111tl Crcc~rrritlo/~lrr)v~i.~\\.it11 res~tltsI'roll~ tlic I%igRellcl Natiotl;~lI';II-k. Amer. Rlidl. N;lt., 75:Gl-100. I)rrr~,\,S, K. 1!)44 Strtdics OII the ~cxrt;~lcyclc ill the lizitrtl, Herr[itinrlyltc.\ /Iavir~iritlis (Ki~ppcl). Ilniv. of Allah;~l)atlStutl., 8:s;-153. El 1II.KII)t.I~. R. I!)J8o (:III)~II licltl studies on terl-itori;~lit! of tile lil;ll.d, .lffoli.s.sng~-pi. Jot~r. COIII~I. I's)cl~ol.,25:!)5-125. 19381) (:or~rtsl~ipI)eli;~vio~- ant1 wxt~alselection of A~rolis.Ihi(l., 26: 175--496. ]!I51 I'ieltl stutlics of the social I)cl~;~viorof thc I)l;~cklilal-d, Clrtto.ccrfrrtr /~c.c.lit~crttr. !\IIIC~.MIIS. No~it., 1493:l-26. I!)(il Strr~ctt~rc;IS rcl;~tctlto I)chavior it1 tllc org;r~~ir;~tiot~of ~)opr~latiot~s in rcptilch: It!: \'crtcl)~.;~tcSpeciation, 148-178. Ilniv. of Tcs. I'rcss, Austin. 1?bl 11 \FIN, \$I, 1';. I! Sc;~son;~lch;~~~ges in testicr~lal- ;~nd epitlitl)rrl;~l histolog) alltl ~1x1-nlatogenicrille in tl~cli~;~r(l Olrr stcr1rs111r)-itrircr.\lc~j~rc,qcr-i. lor~l-. hiorph.. 115: 1.17-4GO. I-IAFIN,W. E., ANI) 1). 121. 'I'I~\'KLI: l!)(i5 lilt I~otly c)c-li~rg;~ntl rspelill~e~~t;~le\,itlcl~cc* Sol- its ntl;iptive kignific;~t~eeto o\;il.i;~li l'ollicl(~(lc\elop~~~e~it ill tile li~;~~-tllllo ,~I~~II.\/~III-~/IIIO.JVII~.1,spt. Zool., I 5H:79-S(i. II,in~~.rri,(;, 121. I). I!Notcs ~II1)reetlillg nntl I-cp~otlr~ctionin tllr li~al-tl.411olis mrolifrcl~iic. Copei;~, 3-5. ~~~AKKIs,1'. '4. I%il '1.11~1,ifc of tlic r;~i~~l)o\~I~I;II-c~. II~I~~II~IISOII-1'l.opic;rI ~IOI~C~~I-;I~I~IS,H~~tcl~i~~so~i ~lll~l(:o,, I.t(l, 1,011~l011. 111 A 11vo1.1:.11.. ANI) 0. J. SFSTON I!)(i(i I-lcrl)rtol';~~~tii~lco~npa~-iso~~s I,etwceli t\vo climatic /ones it1 I'ntiani;~. m me^-. Rlitll. N;lt., 75:fli-(iO. HIRIII.H. I:. I l'l~ccrol(,gy ol 1\50 lil;i~-(lson a t~-opic;il11c:lrh. Ecol. R~OIIO~I-.,SS:S3-1 12. I-Iol~l~~hl<~~:ll,c;. 11. I9(i(i Kcprotlr~ttion it1 wrst(.rl~ 'I'chas Crrc~rrrirlv~)l~o~fr.~.tcxli?~cotir.i (S;I~I-i;~:~l'ciitlnr). (:opci:~,110-1 13. 1101 ION, N., 111 5 11 srll.\ev of atl;rl~tivc,rcl;~rionsliips of tlc~~titionto t1ic.t in thc North All~cric;~~~ Igr~icnitlar.;1n1e1. hlitll. h';~t.,53:SX-1 11. l!j(i2 Iltl~ologicalisolating t~recIi;cnisms in tllc Src./ol)oi~rclo?qurrtirt grorll) of li1;11-tls. I.:volr~tion,16:GZ-74. IN(.I,K, I<. l., IND 13. GI IH\VIN,I.. N I!K5 I I!):$ I 1.i1:irtls ;IS ;I tactol in tlie cont~ol of r;lllge inhects. ]or~r.Erorl. Entolnol., 28:!)!)X-1 004. I!lJ(i I.ir;rl-tl tligcstiol~\trltlics. Her-petologic;~.1 :!I-10. l 1.p-\\ IS, .I., 11. 1!)51 '1 Ile 1)iolog) of I.cio/o/)tst~rnInl~~rirle (S;I!). ;\lnel-. Rlitll. Nat., 45:232-210. I>lc~ll.r,1'. l!)(i4(1 .l'llc tc~~~l)c~-atrr~-ctlepcrltler~tc of ~nyosi~i-;~tlenosi~~ctril~lio\pliotasc;~nd;~lkalinc ~)l~osl)liotascin lirarcls. Comp. Uiochcm. Pl~ysiol.,12:331-340. I!)(i.lO A eolnpar;rtive strldy of tlie tlierm;rl del>elidrncc of contr:tctility in s;~r~rianskele- t;ll l~rl~sclc.C~III~I. Eiocllcln. Pl~ysiol.,13:27-31. I,OKI I9:!(i C:oiltt-il)~~tio~~sto tlie hionolllics, anatomy, ~.cprotlr~ctionant1 developirrent of tlie Intlian l~or~s(~-ge~ko,IIc)~tirlnclyl/c.\ /lnr)iuirirli.s Rlil~pcl.Pal-t 1. Proc. India11 Acatl. Sci., 4:250-281. bl:\v111~w.W. IV. I!)(il 1'lrotol)c~iotlic resl)ollsc of fe~rtalcfi-i~rgc~toed lizai-(Is. Sticn~c.1?14:2104-2105. ID(i3tr Kc,1)1-otl11ctio11in tlic gl.;rrnitc s~~irryliLartl, Srrlo/)orri.\ or-rtifli. Col)cia, 144-152. I!)ii:$O Iiiology of the g~-;cnitc.sl)i~ry li~;~~-tl, Src~lo/)o~-ris 01-rrrlli. 42111cr. Midl. N;rt., 6!):3 10-327. I!)iiI I1l~otol)crioclici-c~sl)ottsc~s ill tl~ret.spc.cics of tlic li/;rrtl geiilrs (!rrrcr. J-lei-l)ctologica, 20:!)5-1 13. l!)ii5o <;I-owtliresl)o~rse to 1)11oto1>~rio(Ii(stitii~~l;~tio~r ill 111~. lil;~t.(l I)i/~.\o\c~ro-~i~ (Io).\crIir. (:0111l). I%ioc.lic~n.I'l~ysiol., 14:20!)-216. I!)ii5b Kel~rotlrrctio~~in the w~rtl-tl~vclliligli/;~rd 111trcr irror?rc~lcr.Her]~ctoIogi~.;~, 21 :3!)-55. I!)iiiicr I ~~cNAI~,1%. I<. I! A 111otlr1of tI~eenergy I)r~tlgetof ;I wild niorl\c. Ecology. 44:521-532. 1!)48 Thc. e:~son;rl I~istologic;tl c.l~;ingcsoctrr~ring in thv ov;c~-y,corl>rls lulc~c~n,;III~ testis of tlte vivil~;~~-orrsli~at-tl, Xnrrlrrticr r~igili.,.L11iiv. (;alif. Pul~l.Zool.. 17:107- 224. 1!)51 So~~ic;rsl>ccts of tlrc life histot-y of the )r~cc;~triglit lilard, Xo?rt~r.\invigilis. Co- l>ei;~,I 14-120. I!! '1'11~c,~rtloct.i~~c I);tsis fol- rel)~-otl~~ttive;~tlal>tations in I-cl)tilcs. In. Conip;~rativc E~~tlocrinology(I\. (;or-l,tnau, Etl.). $!)!)-51ii. ,lohn \\'ilcy ant1 Sons, Inc., N. Y. 1!)5!) Ilrift-f(,~~cctt-;cl)1)ing of lil;~~-tlsOII the Iilack (;;tl, \21iltllifc hia~iagc~nc~itAl-c;~ of soutliwcstern Texas. l'cxas Jour. SL~..11 :150-157. I!)iil 0l)scrvatiotls of tlie ;tctivities of sl~~allani~rials (Rc1)tilia and Mamrn;~li;r)o~r a q~~;~tl~-;rtill .;o~~tltwcst Tcx;ls. Anicr. Mitll. Nat., (i5:127-138. b11 I lI,Ehl,\N, br, I<. 1942 A s11111111;1ryof tltc ig11;11lit1gelills l~~-o,~(iri~r~.x.I511ll. MIIS. (:o1111). Zool., 9:105-181. ~~OIIN'I'.I<. FT. 1!)6:l Tl~e11;1t11ral I~istolq of tlic, rctlLt;~il(,(l.;Lil~h, I:rr~rrt~rr~.cc2gr-cgiri, nail-(I. I\mer. Mitll. Nat.. 70:35(i-385. 1046 A co~r~l)ar:rtivcstutly of tltc ~~rinogenitalsyste~r~ of an ovib,arous and two ovovi- vil)al.ous s1)cc.ic.s of tl~c,li~artl genus Src,lof)o)-I/.\.BIII~. Iltiiv. t!t;~h,37: 1-24. Nolr~.~:,,C;. I<., AND 11. 'I'. RRI\I)I.PY 1!J:13 Tlrc 111atirrg I)cll;rvior of lizirrds: its Ile;rril~g011 111~. tl~coryof sexlial selectioll. i\un. N. Y. 4c;rtl. Sci., :%5:25-100. I'ANI(;I I SI~X.ION.0.1.. II. 11~hI~~~oI.~'. ANI) E. 11. MI.SI:.I.II I!S[.aaonal ~>ol)ul;rtiolrcl~;~~rges ill tlrc li7m-(I, A~rolihli~~~ifro~r\, in Psnarrrs. AIII~I-, hlitll. Silt.. 69:482--l!Jl. s~1.111,11. br. I Il;~~rtll)ookof li~;~rtls.<:o~~rstoch I'u1)I. Co., IIIC.ItIr;rc;t, N.Y. I! b'icltl 11otrs 011 ;I li7;11.d, t11c IIIOIII~I;L~IIswift. wit11 SI)(.C~;I~~cfe~-c~icr to tcrrirol-ial I~clr;i\ioi-.Ecology, 25:233-215. SI.I.IIIIINS,I<. (:.. ,\NI) l~f.1%. OHIN INS ON I!) l(i I~r~r~tlicr;rri;rIysis of :I IIO{III~;I~~OIIof IIIC li/;ir(I .Sct,lo/)or~i.$gr(l(io,$r~\ gr(~cili,\. IJ~iiv. Calif. PuI)I. Zool.. 48: Iil!l-lfi8. l!)(i5 '1'11~AIII/I~I~/I~~II~I~, 111~1e111ntti.slwcics-group (I.acc~rtili:r, Agarnicl;le) in wester11 Austr;rli;r. Jor~r.Roy. Soc. \\fcst. i\ustr;rlia. 14:45-51. I! r\ ~o~~~l)irr;~ti\cpo])~~l;rtinlr st~~dy of sl~iirll vertel)latcs ill tl~eul.anic~rrl areas of tllc LJ11l>cr <:olol-;tdo River basi~rof IJtxl~.Brigliall~ Young Urriv. Sci. Bull., Biol. Scr,, 7: 1-24. '1'1-1 I:ORI), S, I<,, Jn. 1!)5!) A st~ctlyof rlrc s;t~~tlskillk. ,\'c,o.\e/~.\ rr~rioltl~iStejneger. (:opeia, 110-Il!). '~INKI.I..,I). \\'. 1959 Ol)se~~\'atio~~so11 111e Ii/;r~~tls(,'rr~,~~~iilo/)I~or.r~.\ ligri.5, ~~?~~rrridof~/ivr~~.\te.~~~ll~tlr~s a11tl (:~oln/)Iiylrr.\u~i.\li~rri. Sotitlrwc~st. Nat., -1:195-200. I!)(iI I'ol)ul;rtio~~st~t~cture ;inti rc~~~iotluctionilr tlrc lizard l'tn stc~r~.\Orii~icrrr~tstrjne- geri. i\lr~er.blitll. N;rt., (i(i:206-234. I!)(i5n EIfecrs of r;~tliario~~on tlre n:~t:rlity, drrr.;it) and breedirrg str~~ctrrreof n rlat~~ral [)ol)c~l;~tiorrof li7i1rtls. 1 'lir .\ltrrr.\l~r~ricrr~(~.Ilealtli Plrys.. 11:1595-1599. l!i(i51) I'ol)~rl;rtio~ls~rt~ctt~rc airtl effective siic. of a liz;ri-d ~)opnl;rtion.Evol~~tion, 19:569- 573. l!l(i7 1lo111e1:111ge, (Ie~tsity.(ly~r:r~riics ;III(I strrrc~~~~~eof a TCX;IS po1)~rlatio1i of the li/;~rtllit~r ./tirrs/~~~riorin. 111: 1.i7artl Ecology: <\ Syr~lrrl)osium(\\I. \V. Milsteatl, Ed.). Il~~iv.Missouri 1'1c.s~:5-29, 7~'l~til.l~,1). \ti., ANI) 1,. N. ~R\\'IN l!)(i5 I.i/;rrtl ~.el)rotlr~clio~r:rcf~;~c.~or) ~)eriotl ;111(1 ~CS~)OIIS~'10 W;LI.III~II ill lit([ \l(irls- /)r~i~iirri(rf(~~~r;rlt~s. Scie11ti2, I-kS: ItiI 3--l(il4. 71-l~til,~,,1). lv., ANI) I\',(:. ~.A\VRI~NCI: 1956 T%lowgr~~rsfol- ~.el)riles;~~~rl)lilry,. Sor~tl~w(.st. N;rt., 1 : 133-134. TINKI.I?,1). W., 1). NI(;(;m~x.on,:\NU S. I)ANA l!)(i2 Ilo~rri~ra11gt. c,c.ology 01' l'trr ~l(irisIrrrri~~rrir.s/rjrrrge,-i. Ecology, 43:223-229. I'INKI I,, 1). \\I., ANI) I). \,lJoo1)~1{1) l!)(i7 l Ai.re/)trrl for /)rrl)lic-crliorr I~t~hrr~(ir~'24, 1067 A biogeography of rcptiles and amphibians in the G6mez Farias Region, Tamaulipas, Mhico. By PAULS. MARTIN.(1958) 102 pp., 7 pls., 7 figs., 4 maps ...... $1.50 No. 110. Descriptions of tadpoles of Middle American frogs. By PRISCILLASTARRETT. (1960) 38 pp., 1 pl., 33 figs...... $1.10 No. 111. A systematic study of the lizards of the deppei group (Genus Cnemido- phorus) in Mbxico and Guatemala. By WILLIAME. DUELLMANAND JOHN WELLMAN.(1960) 80 pp., 1 pl., 16 figs...... $1.75 No. 112. A Revision of the Ecuadorian Snakes of the Colubrid Genus Atractus. By JAY M. SAVAGE.(1960) 86 pp., 11 figs...... $2.00 No. 114. The Snakes of the Subfamily Dipsadinae. By JAMESA. PETERS.(1960) 228 pp., 8 plates, 11 figs., 12 maps ...... $3.75 No. 122. A checklist of the herpetofauna of Guatemala. By L. C. STUART(1963) 150 pp., frontis., 1 map ...... $2.75 No. 128. Reptiles of Rancho Grande and Vicinity, Estado Aragua, Venezuela. By FREDERICKH. TEST,OWEN J. SEXTON,AND HAROLDHEATWOLE, (1966) 63 pp., 2 pls., 2 figs...... $1.15 No. 131. Intrageneric relationships among colubrid snakes of the genus Geophis Wagler. By FLOYDL. DOWNS(1967) 193 pp., 23 figs...... $3.00 No. 132. The life and demography of the side-blotched lizard, Uta stansburiana. By DONALDW. TINKLE(1967) 182 PP., 4 pls., 20 figs...... $3.75 Cloth bound ...... $4.75 - ture tl;~t;r, by tr;~ckingit~cli\,itlual li~;~rtls ;~ntl by c;~lci~latio~rof the Illcan ree;~l)t~t~'c~';~tlii. A co~nl~;~~.isonof tllcsc tl;~t;~Sol. I)oth C:olo~.;~clo;111tl l~'exas li~;~~,clsis l)~.cse~~cccl ill 7';rl)lc 5.1. tilcs tlc 1;r 1;r;lncc (:c~~tralc.12il)r;~iric, I)clcgrave, Paris.