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FISHERIES RESEARCH /4:*,R.@A~# ii , , (9 F CANAD A L, ' ) \ \:\ MANUSCRHBT REPORT SERIES (BIOLOGICAL) No. '653 AUTHORSHIP Establishment ARCTIC UNIT) 505 PINE AVE, 'd,) MONTREAL, QUE , 2 1 A L \ I,, Datad APR~L1958 A,W, Mansfield The Bialogy of the Atlantic Walrus OdoQems Poçrnarilç ( Linnaex P rosrnarxs 1 i~ the Eastern Cana-dian Arei;icl Aùa tract Sections of molarif~rmteeth rsveai welh definaed hcremental layers tz~hichare almost certâlnly amual In formationJ Cornparison or" speciaens from nor-tbern Eudson Bay and the Bering Sea shows that the Atlantic walrus is slightly smalfer in body size and much shorter in %usk length than the Paclfic walrus, The specinens from Foxe Basin are slightly lasger In body size than those from Hudson Bay, which suggests that comparatively isola'ced breeding groups have been formed, Males mature when six years olci 2nd appeâr to be in rut $rom Movember ts May, the peak of SacedLng activity occurrlog In ApriJ and early May, Th2 youngest sermally mature fernales are five years old, though the majosity do not bueorne mature until seven yeârs, Breedlng maturity may be delayeif â âurther year in most fernales shce frnpregnation does not usually follow the first ovulation, The gestation period lasts just over a year, and the majo~ityof calves are born in April, May o- Jwe, Tne low amal birth rate of 0,3S caEves per adule fernale Is comterbalanced by great materna1 solici-kuds for the calf with a correspondangly TAULE OF COTiTENTS Page LIST OF TABLESeeaeo.ee,eeo**.ae.eoeee***aiieee*ae***eeeeo*~ LIST OF FIGU"nESesee~eoe*eoOooooocceoee~~*eee*eeeee.~eeeoaa~i LIST OF APPENDICES~oea~eeea~*eeoa~oasoes~~e~et>oeee:< ACKTJO\JLL;DGK~~TI\TTSooee e ee eo Je.0 a o 0.90 e e e o .e oaeaoe eao.ed IWRODUCTLOI$aeeoeeoooa~oseo~ooeoeoYeveoe*aseo****~eeeo~e.1 General Rema~ks,.~.~~~~~~~~~.~~~~~~~~~~~~~~~~~~~1 Previous Blorlr ..,,...oo,oe.00.e~~8eOBuO(LOd~BOI)e~ 2 ~o~~~c~~~u~~~.~,,~,~~~~~~~~.~~~~~~~~~~~~~~~~~~~~3 KETBODS AND bLnTERIALSoaoo,seeo0eoeo*eooi~+osseee*so~eoe~e5 Field Localitieso9eOB0...B~~O~P~B.oOOP.~VOP000ee5 Northern Hudson Bay,, ..,..............,.,...,,5 Northern Foxe Basin,o...e~o,..,e..~e~e~.BO~O038 n lravel~oJOOÎOe~~POo~~~g.U~~OoO~ODO~Oe~~e~ee~o~ee~~L~ C~~~t~~eeoaoee~*e~osseoeeee~eeee*eoeo.~~~oeoauoo~~ Marking POoDO~~~O~e~~OeO~OODO***UO~~D~~O~~~~~o~oO~~ Materials C~Lfe~t~d~~~~~~.~~..~~~~~~~~~~~~~~~~~~15 n~reatrncnt of MateriaPs....e..OOl.deaeOeOe~OOOoOe17 AGE DETERMI~~ii1TION~oO.ORb~esOO~~e~~~~~OO~e~~~~~eee~~~~~~a~153 M~~h~d~~~~~~~~..~~~.~~~~~~~~~~~~~~*~~~~.~a~e~~o~19 Body length me~s~~~~ents,..,,~...~~~~~~~~~~~~~3-9 Tusk and baculum measurements,,,.o,..~~OO.~IoO~~ ~~a~s~.~.~~.~~~.~~.~~~~~~~.~.~.~~.~~~~~..~~~~~23 Teeth e~O~JOIe~~OIee~~B~~O~ss~O~~~~~~e~~~~~~~oo~~ iTJ PAGE Fasting ........~e~o~~~e~.O~.~~<d.~~~OD.~~~.~~..~.~~~~ TIE MOULT ............o~~~e~~~~e~~.~~e~.~~.~~~.o.~e....o~6 TKT-, MAL3 REPRû"UUCTTVT-, CYCLEeeeeeemeee*eeeaaoeueeeeee4ee79 SexuaL llaturity 04aopo*9bee~s9e.ee-0.a*.e**e.weem*Q79 Crowth of the baculum and teçti~,,.~..~.~~~.~79 His tology of the testis and epididymis ..... ..80 The Testicular Cycle in the Adclt Male ........... .84 Chronology of Events In the.Adult Male ............85 THE FEPLALE REPRODUCTIVE CYCLEeo, ....ee..e~e~.D0.ee.o00088 Sexual "laturity.............e........-...........088 Ovulation in nulliparous fernales., .......... -89 Ages at first ovulation.e~~~aa~~~~~s~eOe~~aD~8~ Birth Rate .........................................92 The Ovarian Cycle 0a~~~~~e~~eOIOo~e~D~O~eeoeELD~d~O~3 Development of the follicles and ovulation..,33 The corpus luteum ......s.OO..O.e.......B.b~. *97 Implantation and Growth of the Embryo .............102 Birth and Care of the Young o~e..a...e..~.o.~.~e0107 Chronology of Events in the Adiilt Fezale.. ........108 DISTKIBUTION AND rlli3UiJDANCE ..,..........O.eeO.~~~~...e~,~lL Relation to th9 Land .,,........e....e.....Je.~eeeI112 Relation to Sea Ice .......... 800...,ees...*"gt.e8B115 Local Movements and Migrations,. .......~a.Oe..e.ilBS_l~ S~4?4ARYesoeeeeeaO.e..s.ee*oeeooee...e.eeaa~ee-eoo..eeeel22 BIBLIOGRAPHY e**ee6~.~..0..~.~-.e*.~.~~*oe.a.~*oee~26 LIST OF TABLES TAB LE PAGE 1 Weights of Various Interna1 Structures of an AduEt Male Atlantic 46 II Comparative Sema1 Dirnorphisrn in the W~L~US~~~~...~~~.~~~~.~~...~~~~.~.~~.~~~~~~ III Observed Variations in the Dentiti~n,,..,~~~ IV Food Organisms taken from Stonach Contents89ee.b.0e.ee.eceee.eQ~.eBe..eee~~~8. V The Mou~~,~~~~o.~~~oB.o~o.*oQ=o~Bo.~oooooo.Q VI semal Waturity in the Female,,,eoe.see..s.s VI3 Calculated Average GestatFon Period derived from Lengths of Eleven Foet~ses,.~, LIST OF FIGURES FIGURE PACE M2p of Southû.mp-ton1s land sfios?ing pos itio~ of Ud.j& and Lirnit of Winter Fast Ice, a a ., Map of Foxe Basin showing Bathymetry and Limit of Winter Fast IC~.....,.~~~.~~~.~~ Stainless Steel Tag used in marking 3Jalrus,, Froquency Analysis of Body Length Measure- ments in In~hes,,,,,,~~~~.~~~~~~~~~~~~~~~~~ Cornpôrlson of Tusk Growth in a Foetal, %?O Year Old and Adul'c Male I.Jalrus,o.g.Buesoooo Cornparison of Male and Female Tusk Lengths in th3 First Yiiree Years of Gro~qth,. ,. Photograph of the Tusk of a 21-Pear-Old Male to show Root Ridges and Medial Depressions. (a) Illustration of the Root Xidges on an aLufJa1.e Tusk after exfoliation of the Cemen-t;um (b) The Dentine and Cemen-tu~nLayers on the Tusk Roo-L in Longitudinal Secti~n,.,......~.~.., Longi-tudinalSection of the Lowr Molar Too-th of a 7-Year-ûld-Female ( x 3e5)01*ec*eeeo9* Part of a Transverse Section of the Lower Canine Tooth of a 21-Yeas-Old Male (x IS),, Deposition of Cementrun on th8 Roots cf Molar- if orm Teeth in Males and Femal-es ,, , , , , , , *,, FIGUHE PAGE 12 Grotrth in Length of the Body of Iiialss arrd Female~...~....lOda.e*....e*. ............... @ 13 Increase in Yelght of the Body ( the treights of 4 males and 6 females of unknown âge are taIren from Loughrey, 1955). ............. 47 Grot~thin Lexgth of the Tu~ks...~~........a..e 51 15 Growth of the Bacul~n........,...~~.~.~,~~.~~~% 16 Head and Shoulders of an Adult Male Walrus showing Epiderrnal Tubercles and Scars from Tusk Inflicted Wounds........... ..a.......e. 59 17 Read of an Old Adult Male Walrus showing Worn Tusks and Vibri~sae............~~...~~~.~... 59 18 Dentition of the Full-Term Foetus A 11 (Teeth indicated by bracketed nunbers were not observed in the specirnens available, but were inferred from Fayls accouni of the Pacifie walrus) ............................. 61 19 Percentage of Stomachs containing Fo~d...,~... 75 20 Development of the Testis (the specimens in breeding condition are indicated by black dots).. ..................................... 81 21 Section through the Seminiferous Tubules of the Immature 6-~ear-~ldIdIale R 111 (x 600)...... 83 FIGURE 22 Section through the Zpididymal Epithefiwû of the Immature 6-~ear-0ld Male A 111 ( x 600)0~10ee~es01~010au~~*4*~.~re~*eeil~~~ 23 Section through the Epid.idyrnal Epithelium of the Mature Male A 97 ( x 600).,.......,.,,, 24 Section throggh a, Serniniferoias Tubule of the AduEt Male 1W IO4 taken on Eovember 30: Type A ( x 600)~e.e**e*~*~~~~**OeesOOO~e8ee 25 Section through a Seminiferous Tubule of the Adult Male A 97, taken on June 17: Type B ( x 600)0~~*ee..e~**e4.e.~e~*s~eeee.~c.eeoe 26 Section through a Seminiferous Tubule of the Adult Male A 62, taken on September 18: Type c ( x 600) ~O1e~e.O*~~e.LeLLO*oeee~~OB~Be~~O 27 Çeasona.1 Fluctuation in Dia.rneter of the Semin- iferous Tubules in Adult Males (the tira Specimens indicated by black dots are in an active state of Sperrniogene~is...,..~~~~ 28 Relation between Age of the Famale and Number of' Corpora. Lu-tea in the Ovarie~....~...,.~, 29 Section of the Corpus Luteum of the Pregnant Fernale A 42, taken on August 7 (x 600). .. ,. 30 Section of the Lâte Pregnancy Corpus Luteum of Female A 9, taken on May 26 (x-600),, . ,, 31 Section of the Regressing Corpus Luteum of Fernale A 43, taken on August 17 (a ~oo),.., ix FIGURE PAGE 32 Section of a Corpus Luteut? Spuriun from the Barren Female A 77. taken on October 2 ( x 600) .................................. 101 33 Growth of the Ernbryo and Placenta. ............ 104 34 Growth of the Hman Embryo (after Arey, 1954) . 105 35 Map of the Eastern Canadian Arctic ............ 118 LIST OF fiPPENDICES APFELùD IX 1 Body and Tusk Length i.Ieasurûments of 83 Kale and 39 Female kfalrus of Kno.r\rn Hge.9.8.~9DI..01.D0Ba~.0Bee(i~eeO(I~P~O~e~132 II Development of the Testis in Imrnature and Mature MaPese,.Be.~e0.0..0P~'10.~OeBe9Be136 III Development of Follicleç and Corpora Lutea in the Ovaries of 59 Atlantic ~~a~ruçO,..o.e.O.E..~BO(tea~~e~eaDD1.~O..Ol.Be138 IV Growth of the Hwnan Embryo ( after Arey, 1954) ~~e~~e~~~.~.~~I)OasBBe~DOi)OOePOed145 V Cornparison of Mean Body Length and PIean External Tusk Longth in Plale Atlantic and Pacif ic klalrus.. -..a *. o. e.. *.. .. IL6 The Initial part ol the iabora tory work on t.rhfch this study Is based -+ras cxrried out An the Department of ZooEogy, McGi%7 Vni~ersity~I am most gsateful to Pro- fsssor J, Stanley for supplying labofatory fac3Pit2es3 and to Dr, Mu J, Dmbar for initiatfng the program of reseasch and offerhg much uselul adviee and criticlçn dwhg its cornpletion, Since April 1956 the work has been suppor-ted by the Flsheriec Research Board, Arctic Unit, ar,d 1 wiçh to thanlc Dr, H, D, Fisher and his staff for much valuable assis tance Y Research on the Atlnntlc walrus was begm by the Ffshrrles Research Board in 1953 as part of the generaX study of the marins resoxrces of northern -+ïrrters, I am gratefub to Dr, Duabas fur directhg the researeh initially and for designhg the tag used in rnarking expvrLmonts, Dr, E, H, Graingsr began the -kagging program at Coats lslaad in 1954, and alsû made the f irst substantial co'ilecti.on of reproductive mate~ial, Further collections were made frorr! C uGuMeVe." Calamu&' during the psriod AugusU 1955 - Septernbei.