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Faculty Publications from the Harold W. Manter Laboratory of Parasitology Parasitology, Harold W. Manter Laboratory of

1953

On the Land Mammals of St. Lawrence Island, Alaska

Robert L. Rausch Arctic Health Research Center, [email protected]

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Rausch, Robert L., "On the Land Mammals of St. Lawrence Island, Alaska" (1953). Faculty Publications from the Harold W. Manter Laboratory of Parasitology. 524. https://digitalcommons.unl.edu/parasitologyfacpubs/524

This Article is brought to you for free and open access by the Parasitology, Harold W. Manter Laboratory of at DigitalCommons@University of Nebraska - Lincoln. It has been accepted for inclusion in Faculty Publications from the Harold W. Manter Laboratory of Parasitology by an authorized administrator of DigitalCommons@University of Nebraska - Lincoln. Rausch in MURRELET (May-August 1953) 34(2).

ON THE LAND MAMMALSOF ST. LAWRENCEISLAND, ALASKA Robert Rausch The mammalsoccurring on St. LawrenceIsland representspecies which are widely distributedin borealregions. They are not well known, hoiwever, and arepoorly representedin colIections.In the past, some of thesemammals have been regardedas being specificallydistinct from closely relatedforms occurringon the adjacentcontinents. It is the purposeof this paperto present somenew dataon thesemammals, with particularreference to theirtaxonomy. Begunin the winter of 1950, the investigationof animal-bornediseases on St. LawrenceIsland has been carriedon by the Animal-borneDisease Branchof the Arctic Health ResearchCenter, located at Anchorage,Alaska. The collectionof mammalshas been an importantpart of this work, and a largevolume of materialhas been assembled.With the exceptionof an occur- rence of unusual mortality in walrus during 195lt reportedseparately by Schiller (1953), nothing of extraordinarymammalogical interest involving the marineforms has beenobserved. St. LawrenceIsland, of volcanicorigin, is about 90 miles long. It lies in the BeringSea about 104 milesfrom the nearestpoint on the Alaskanmain- land, and 38 milesfrom CapeChukotskyi, Northeast Siberia. Low mountains, few exceeding1000 feet in altitude,cover nearly half the total surfaceof the island. Steep cliffs, the nestingplaces of great numbersof sea birds, border the sea in the mountainousregions. Mucl]of the islandis low and wet, with numeroustundra ponds. Here,vegetation is characteristicof wet tundra. At higheraltitudes the vegetationis typicalof dry alpinetundra. The two villages,Gambell (Sevuokuk) and Savoonga,are inhabitedby about 500 SiberianEskimo. These peopledepend largely upon marinemam- mals, particularlywalrus, for food. Severalhundred sledge dogs are kept by the Eskimo,but these are, in general,closely confinedto the vicinity of the dwellings. About 400 reindeerrange in remoteparts of the island. These are descendantsof animalsintroduced during the early part of the century; at one time the reindeernumbered more than 10,000. Poor rangeconditions have been largelyresponsible for the heavy losses which have occurred.No managementprogram is now in force,but killing of the animalsis prohibited. Sevenspecies of mammalsare indigenous to the island;others appear from time to time via the pack ice. Speciesfor which materialor informationhas been obtainedare consideredseparately: Sorex tundrensisjacksoni, Hall and Gilmore, 19 3 2. Tundra shrew. Shrewshave been uncommonon St. LawrenceIsland during the last three years,and efforts to trap them were unsuccessful.A specimenwas taken by an Eskimoon January13, 1952. Mr. FrancisH. Fay, Departmentof Zoology, Universityof British Columbia,also collecteda single shrew. This animaI, madeavailable to the writer,was takenon July 18, 1952, and containedseven embryoseach measuring4 mm. in greatestlength. Sorex jacksoniwas describedon the basis of 16 specimenscollected at Savoonga. Sincethe writer'smaterial was inadequatefor study, six skins and skulls wereobtained on loan from the originalmaterial. At the time of its description,S. jacksoniwas recognizedas showing a close relationshipto the "Sorex arcticusgroup." It was differentiatedfrom S. tundrensisMerriam, occurring on the Alaskanmainland, on the basisof size differenceand slight relativedifferences in certaincranial proportions (palatal lengthand crarlialbreadth). As far as the writercan determine,the two forms are identicalin characteristicsof dentition. The differencesas definedin the originaldescription of S. jacksoniappear to havesubspecific, rather than specific, value. Consequently,it is concludedthat this form is more appropriately

(18) Rausch in MURRELET (May-August 1953) 34(2).

19 THE MURRELET Vol. 34(2) designatedS. tundrensisjacksont. A singleform of the tundrashrew, S. t. tun- drensisMerriam, is recognizedon the continent. The statusof the specieshas been discussedin some detail in anotherpaper (Rausch, 1953), Ursusarctos Linnaeus Brown bear. Geist (1934) reportedthe occurrenceof a brown bear on St Lawrence Island during the summerof 19 3 3. The writer has obtained no further informationon the occurrenceof this speciestand it must be assumedthat the individualobserved reached the islandby way of pack ice from Siberia. The raceof U. arctosoccurring in NortheasternSiberia and Kamchatkais Uv arctos beringianusMiddendorff. Thalarctosmaritimus Phipps. Polar bear. While neverabundant around St. LawrenceIsland, polar bearsprobably come on shoreevery year Tracks are seen from time to time in the winter as on travelson the uninhabitedpart of the islandf Bearfrequently spend the summeron the island, but inhabit only the more remoteregions. The skullsof threevery largeold maleshave beenobtained from Eskime at Savoonga. The cranialmeasurements of thesespecimens are includedhere:

Max. Orig Inter- Pal. Post- Squam. Mast. tooth No. Cbl. Zyg. orb. L. Pal. L. const. W. row 12626 407.7mm. 256.4 107.3 198.6 202.3 169.2 194.9 139.0 12628 408.1 260.0 105.1 200.5 200.8 198.8 146.7 12627 409.4 250.2 103.9 209.3 193.4 170.8 191.8 142.3 Canistupus Linnaeus. Wolf. Murie (1936) reportedthe occurrenceof a wolf on Stv LawrenceIsland during 1927. The animalwas not killed, but eventuallydisappeared. As far as canbe determined,there has beenno otherrecord of this specieson St. Law- renceIsland. This wolf also must have arrivedon the islandvia the packice. Such an occurrencewould be unusual,since wolves do not rangefar out on the sea ice and therewould consequentlybe little chancethat they would be trappedon the moving floes. Vulpes vulpesLinnaeus. Red fox. Although Murie (1936) reportedthat red foxes are occasionallyseen on the island,it has not beenpossible to secureany specimens.None has been trappedin recentyears. Accordingto the work of Bobrinskiiet al. (1944) and that of Ellermanand Morrison-Scott(1951), the name for this form would be Vutpesanulpes Linnaeus. The red fox is now either very rare or nonexistenton St. Lawrence IsIand. Although Murie ( 19 36 ) had a considerablenumber of red fox mandibleswhich had been excavatedfrom old habitationsitest he concluded also that the arcticfox (see below) 'fhas been the dominantform." It is possiblethat past conditionshave been such that animalscame in from time to time on the pack ice and colonizedthe island, but they have not become permanentlyestablished. It is almost certainthat such animalswould come from Siberia. If such is the case the form would be V. sulpes beringiana Middendorff,which, accordingto Ellermanand Morrison-Scottsoccurs in 44North-EasternSiberia, includingKamchatka and Anadyr region." There is an obviousneed for reconsiderationof the red foxes of North Americain light of the work of Old-World investigatorswho have concludedthat Vutpessutpes is a Holarcticspecies Rausch in MURRELET (May-August 1953) 34(2).

May-August, 1953 LAND MAMMALSOF ST. LAWRENCEISLAND 20 Alopexlagopus lagopus Linnaeus. Arctic fox. During recentyears the arcticfox has been abundanton St. Lawrence Island,concurrent with a high populationdensity of voles. One hundredsix foses have been autopsied,and a total of 38 skulls with full data has been preservedfor study. In addition,some observationshave beenmade on pelage color and molt in captiveanimals obtained as pups. The St. LawrenceIsIand arcticfox previouslyhas not been studiedin detail. The arcticfox of St. LawrenceIsland was first studiedwith the hope that somethingof the origin of one of its endoparasites,pathogenic in man, might be disclosed.These foxes are commonlyinfected by a tapewormof the genus Echinococcus(Rudolphi, 1801), the larval stage of which occursin voles (Microtusand CtetE2rionomys).The life cycle of this parasitehas been thoroughIyinvestigated in the laboratory,and it has been establishedthat it differsfrom the formoccurring in North America.Barabash-Nikiforov ( 1938) reportedabout 50 per cent of the red-backedvoles, C. rutilusPallass infected with Echinococcuslarvae on Bering Island, and Afanastev(1941) observed the samerelationship. It has been concludedthat the BeringIsland-St. Law- renceIsIand form of Echinococcusis that which causesalareolar hydatid disease in man in south Europeand Russia (Rausch,1952b)+ All suchevidence sup- ports the hypothesisthat the arcticfox of St. I awrenceIsland is the same form which occurson the mainlandof Siberia. Skulls of the subspeciesof arcticfox which occurin Siberia,Alaska, and on the arcticislands, have been obtainedfor comparativestudy. Unfortun- ately, largeseries of A. Iagopustagopus from the Siberianmainland are not available,but the skullsof four specimensof arcticfox from Nizhne-Kolymsk andone fromthe mouthof the LenaRiverfi were obtained. Skulls of A. Iagopus beringensisMerriam. A. Iagopuspribilofensis Merriam, and A lagopusin- nuitusMerriam were also compared. Regardingthe status of the St. LawrenceIsland fox, Murie (1936 p. 339) stated, "Consideringthe apparentease with which foxes can and do immigrateto St. LawrenceIsland on floating icet it is not likely that an insular form peculiarto that island is to be found Proximity to Siberia would suggestspecific affinity with the Siberianfoxes.t' It is evident that currentsin BeringSea are such that ice and other objects (carcassesof marine mammals,etc.) arecarried from Siberiato the shoresof the island. The writer has not been able to differentiatethe St. LawrenceIsland form from the Siberianform on the basis of cranialcharacteristics. The obvious conclusion is that they are all of the samesubspecies, A. Iagopuslagopusv It is also desirableto clarifythe relationsfiipsof the St. LawrenceIsland form to that occurringin mainlandAlaska. Severalsubspecies of arcticfox were definedby Merriam. He describedA. Iagopushallensis (Hall Island) in 1900, andA. Iagopuspribilofensis (Pribilof Islands)t A. Iagopuslvering- ensis (Bering Island), and A. lagopRs innuitus (arctic Alaska), in 1902. In attemptingto evaluaterelationships, it is first necessaryto gain some understandingof Merriam'sspecies-concept insofar as these animalsare con- cerned. This is best exemplifiedby his interpretationof materialfrom the Pribilof Islands. Merriam(1902; p. 168) recognizedthree "forms"of arcticfox on St. Paul Island on the basis of cranialdetails. Unfortunately,the numberof skulls studiedwas not stated. Merriamconsidered three possibilities regarding theseforms: '(1) that the largeskulls representa Iargeresident species while the two othersare stragglersfrom St. Matthew (or some other) Island and the mainlandrespectivelyt reaching the Pribilofs by meansof the pack ice; (2) that the large skulls representa large residentspecies; the small ones Rausch in MURRELET (May-August 1953) 34(2).

21 THE MURRELET Vol. 34(2) straggIersfrom St. Matthew (or some other) Island, while the middlesized ones arehybrids between the two; (3) that all threebelong to a singlespecies which presentsextraordinary and unprecedentedvariations in size." Merriam acceptedthe secondhypothesis and namedthe large form Vulpes pribilofensis (=A. Iagopuspribilofensis). In consideringthe racesof the arcticfox, it must be kept in mind that isolation of any insularpopulation is impossible. These animalstravel far from land upon the sea ice, alld arecarried great distances on ice floes. Merriam statedthat arcticfoxes comeashore on the Pribilof Islandswhenever the pack ice extendsthat far south. It is well known that foxes are often transported in this mannerto St. LawrenceIsland, and the samemust hold true for Hall, St. Matthew,and BeringIslands. It is obvioussthen, that theseislands might receiveanimals from any islandslying farthernorthy as well as from both continents. Regardlessof origins, it is evidentthat new animalsarrive every year on the northernislands, and less frequentlyon the Pribilofs, which lie relativelyfar to the south. A large form on the Pribilof Islands would not maintainits genetic identity by selectivebreeding in the presenceof animals representingother forms;the popuIationwould consistof the productof t}}einbreeding of such formsas mrerepresent. In the writer'sopinion, Merriam'sthird hypothesisis the only one that could be consideredvalid; that ist the Pribilof Island foxes show muchindividual variation in size, as do all popuIationsof the arcticfox. Materialat hand does not permitfinal conclusionas to whetherA. lagopus pribilofensisis distinctive,but furtherstudy involvingadequate material prob- ably will disclosethat it is not. The nameassigned by Merriamwill have to be retaineduntil such study has been completed. It is significantthat only two forms of arcticfox are recognizedon the Siberianside of BeringStraits; these are A. lagopuslagopus, which rangesfrom Norway to NortheastSiberia, and the insularA. Iagopusberingensis. A largeseries of arcticfox skull have been collectedfrom arcticAlaska. Includedare 17 skulls from Point Barrow,the type locality of A. Iagoptis innuitus. About 20 specimenswere obtained at Wainwright;several were securedat WalesfiPt. Lay, and fartherinland. With thesespecimens as with all others studied,a high degreeof individualand age variationin cranial charactersis evident. Variation is noted particularlyin actual size, length and width of rostrum,degree of developmentof medianfrontal sulcus, degree of inflation of frontal and temporal-parietalregions, and in size of teeth. Merriam ( 1902; p. 170) differentiatedA. Iagopusinnuitus from A. lagopuslagopus as follows: 'sSimilarto lagopusin size and generalcharacters, but braincasebroader and more pyriform,and taperingmuch more abruptly behindbroadest part; nasalsmuch broader.' Comparisonof topotypespeci- mens with the five specimensfrom Siberiahas disclosedno differences.Shape of braincaseis quite variable. There was no difficulty in findillg Alaskan specimensin which the width of the nasalbones was exceededby the Siberian specimens.On the basisof directexaminationt it was not possibleto distinguish A. Iagopusinnuitus. Comparisonswith the St. LawrenceIsland materialIed to the same conclusion.Since material in this casewas adequatesseries of the two nominal formswere compared statistically. To do this, a seriesof maleand a seriesof femalesfrom St. LawrenceIsland and the arcticcoast of Alaska (Pt. Barrow and Wa;awrightonly) were selectedat random. Sinceboth serieshad been collectedat a time when the populationwas very high and duringthe same months of the yearythey were consideredcomparable in regardto age com- position without selectionfor aduIt specimens.The male and female series Rausch in MURRELET (May-August 1953) 34(2).

May-^ugust, 1953 LAND MAMMALSOF ST. LAWRENCEISLAND 22 from St. LawrenceIsIand were paired at randomwith the correspondingseries from the arctic coast. Statisticalanalysis (see Table I) failed to disclose significantdifferences in any of the nine characterscompared. A. Iagopusinnuitus cannot be distinguishedfrom the form which occurs on St. LawrenceIsIand. Since all evidencesupports the opinion that the St. LawrenceTsland form is identicalfrom A. Iagopuslagopus of Eurasia}it follows that a single, highly rariable form of arctic fox has circumpolar distribution. Otherpertinent data are includedin Table IT.

TABLE I Companson of cranial measurementsof randomly-pairedgroups of skulIs of arctic foxes from St. LawrenceIsland and mainland Alaska.

Measurement M a I e s F e m a I e s (in mm.) No. Mean Std. error No. Mean Std. error Pairs diff.t mean diff. t Pairs diff.* mean diff. t Condylobasal length 16 .235 1.507 .1500 20 .134 1.470 .091 Zygomatic width 17 .170 .602 .2833 21 .309 .908 .3409 Interorbital width 17 .200 .362 .5520 21 .538 .393 1.370 ** Palatal length 16 .35 0 .825 .4242 21 .404 .915 .4424 Post-palatal length 14 .371 .917 .4050 20 .550 .835 .6590 Squamosal constriction 16 . .425 .744 .5712 21 .133 .554 .7600 Maxillary tooth row length 17 .476 .627 .2401 21 .027 .619 .4384 Nasal length 16 .076 .711 .1070 21 .012 .914 .1354 Nasal width 16 .000 .000 .000 21 .018 .232 .0780

*All values of t under l.Q0 are associatedwith probabilitygreater than 30 per cent, values under 0.70, with probability greaterthan 50 per cent. **t equals 1.47: 20% > P > 10%.

> .. S . S n TABLE II Averagecranial measurements of arcticfoxes from St. LawrenceIsland and mainlandAlaska. (in millimeters)

Condylo- Zygo- Inter- Post- Squamo-Maxillary basal matic orbital Palatal palatal sal con- toothrow Nasal Nasal No. Sex length width width length length striction length length width

St. LawrenceIsland 21 f 117.8 65.8 26.9 60 56.3 41.8 54.5 43.6 10.1 17 m 123.8 68.7 27.6 62.3 58.3 43.9 60.3 45.1 10.9 MainlandAlaska 26 f 118.1 65.8 26.4 60.6 53.6 42.8 54.7 43.3 10.9 21 m 121.8 68.5 27.4 62.6 57.4 43.1 56.2 45.4 11.1 Rausch in MURRELET (May-August 1953) 34(2).

23 THE MURRELET Vol. 34(2) Citeltusundulatus Iyratus HaIl and Gilmore. Groundsquirrel. Ground squirrelshave been rather common on St. LawrenceIsland during the time of our work. The skulls of 85 specimenswere preserved for study. Citeltusundulatus, the long-tailedsuslik, is widely distributedin Asia and borealNorth America. The taxonomy and distributionof the Alaskan subspecieshavebeendiscussedinanotherpaper(Rausch, 1953). Ognev (1947) has discussedthe Siberianforms in detail. Hall and Gilmore(1932) basedtheir descriptionof CitellusIyratus on seven specimenscollected along the north coast of St. LawrenceIsland. These writersconcluded that the most nearly relatedform is C. buxtoniAllen (=C. undutatusleucostictus Brandt), of northeasternSiberia. Sevenskulls of the latter, from East Cape, and Emma Harbor,Siberia, were availableto the writer for comparison.Some cranial measurementsof the two formsare shown in Table III. Of the 85 specimensmentioned above, all of which were collectedin August, 1950, 46 were malesand 39 were females. The majoritywas com- prisedof young of the year. Forty-two malesranged in weight from 286 to 586 grams (av. 449.0 grams), and 30 femalesranged from 344 to 532

TABLE III Cranial measurementsof Citellusundulatus from St. Lawrence Island and Northeast Siberia. (in millimeters)

Condylo- Zygo- Inter- Post- Length Squamo- Mas- Maxillary basal matic orbital Palatal palatal palatal Nasal sal con- toid tooth row Sex length width width length length foramen length striction width length

Citellusundutatus Iyratus f 52.6 36.4 12.5 28.5 21 3.9 20.3 22 8 24.2 11.5 52.3 35 12.6 28.7 20.9 3.8 19.6 2.2 23.5 11.8 51.9 34.6 12 28.6 20.5 3.7 19.1 21.9 23.5 12 51.7 34.7 12.2 28.2 20.2 3.9 19.2 21.9 23.1 12.5 50.7 33.3 12 29.6 18.5 4.1 18.7 22.1 23.1 12.7 49.8 32.4 11.4 28.5 18.5 3.9 18.3 21.7 22.5 12.5 m 54.2 36.7 13.3 29.8 21.7 3.9 20.7 22.8 24.6 12.1 52.9 34 12.2 31 19.4 4 22.8 23.8 12.5 52.7 34.5 12.5 30 20 4 20.5 22.9 24 12.8 52.1 33.1 12.1 30.1 19 4.1 19.3 22.9 24 12.6 52 33.8 12.1 30.2 19.5 4.5 20.2 22.3 23.8 12.2 50.5 32.6 11.4 29.5 18.4 3.9 19 21.7 22.7 12 Av. f 51.5 34.4 12.1 28.7 19.9 3.9 19.2 22.1 23.3 12.2 Av. m 52.4 34.1 12.3 30.1 19.7 4.1 19.9 22.6 23.8 12.4

Citellusundulatus leucostictrus f 51.7 35.8 12.1 31 20.4 3.8 19.9 22.4 24.5 11.8 51.4 36.4 12.4 29.9 20.9 3.7 19.2 22.3 23.2 12.5 51.3 36.8 13.3 30.5 20.5 3.6 20.3 22.2 23.9 12.1 51.1 35.5 12.5 30.3 19.8 3.5 19.5 22.3 23.6 11.4 m 54 37.3 12.1 32.1 21.8 4 20 22.6 23.4 12.2 13.1 20.6 12.5 47.9* 30.5 11 31.3 17.2 3.7 18.6 22 23.1 Av. f 51.4 36.1 12.6 30.6 20.4 3.6 19.8 22.3 23.8 11.9 Av. m 50.9 33.9 12.1 31.7 18.5 3.8 19.7 22.3 23.2 12.3 *Immature animal. Rausch in MURRELET (May-August 1953) 34(2).

Mag-August,1953 LAND MAMMALS OP ST. LAWRENCE ISLAND 24 grams (av. 434.0 grams). Twelve animalsranged in weight from 600 to 800 grams,while one was too badly damagedby the shot to be weighed. No pregnantfemales were includedin this series,since breedingoccurs only . n eary sprlng.. Dicrostonyxtorquatus exsul Allen. Varying lemming. Only two specimensof this lemminghave been obtainedfrom St. Law- renceIsland in more than threeyears, and it is evidentthat it has been at a very low level of populationdensity. Allen (1919) basedhis descnptionof D. exsul on four specimenscoIlected by Joseph Dixon in 1913, and thereis no recentinformation that this form ever becomesvery abundant. On the other hand, Nelson (1887) stated, regardingCuniculus torquatus (= D. torquatus): "On St. LawrenceIsland and the Bering Straits Islands and adjacentcoasts it is very common." When D. exsul was described,available material for comparativestudy was inadequateto estabIishdegree of relationshipof this form with those of the adjacentcontinents. The writerhas had for study but five specimens of this lemming,but a greatdeal moreinformation is now availableregarding the others. The work of Ognev (1950), who has concludedthat a single Holarcticspecies exists, is particularlysignificant. On the basiscf comparisons with a greatdeal of Alaskanmaterial, and with limitedmaterial from Siberia, it is eviden$that such s}ightcranial differences as exist have no specificvalue. Allen (1919; p. 533) calledattention to the palenessof color in this form, a characterof value at the subspecificlevel. D. torquatusexsul is palerthan D. torquatusrubricatus (Richardson), of mainlandAlaska. and its colorsare very much subduedin comparisonwith D. torquatuslenae Kerr, of eastern Siberia. Apparentlythe winter pelageof the St. LawrenceIsland form has not been observedpreviously; one of our specimenswas taken in winter, and it showedthe characteristicwhite pelageand highly-developedsnow claw. The form was designatedD. groentandicusexsul by Rausch (1952a), but in a more recentpaper (Rausch, 1953), the speciesname D. torqustus was appliedin agreementwith the Old-Worldinvestigators. Clet1xrionomysrutilus albiventerHall and Gilmore. Red-backedsole. The red-backedtrole was also difficult to collectduring the time of our work, and only four specimenswere obtained. This vole was describedby Hall and Gilmore(1932) on the basisof threespecimens collected at Savoonga. At the time of its description,this form was consideredspecifically distinct. Apparentlyno additionalspecimens have been collecteduntil recently,and the form has not beenstudied further. Rausch (1950) revisedthe status of the red-backedvoles specifically designatedas C. dawsoniMerriam, and concludedthat it is conspecificwith C. rutilusPallas, previouslyregarded as Palaearcticin distribution.For lack of material,C. stbiventerwas not considered.More recently, Rausch (1952a) appliedthe nameC. rutitusalbiventer to the St. LawrenceIsland form. Hall and Cockrum(1953; p. 385) retainedthe originalname. In regardto its affinities, howevert they stated, "CloseIyrelated to C. rutilus, but skull larger." It is true that this is one of the largest,if not the largest,form of C. ratilus. In this regard,it is analogousto the St. LawrenceIsland tundra vole, Microtusoeconomus innuitus Merriam, discussed below. In the writer's opinion,larger size alone does not constitutespecific difference. Hall and Gilmorecompared their specimenswith C. ruttlus jacutensts Vinogradov.of the Iakutskregion, Siberia, and concludedthat it differedfrom this form in having t. * * the palatalbridge less completeand the antenor, re-entrantangle of ma shallower." Minor external and cranial differences Rausch in MURRELET (May-August 1953) 34(2).

25 THE MURRELET Vol. 34(2) weredescribed as a resultof comparisonswith C. dauesoni(= C. rutilusdaw- soni). Color characteristicswere also defined. In additionto the writer'smaterial, three additional skulls of C. rutilus albiventerwere examined. It is evident that the skull of the St. Lawrence Islandform is moremassive that that of the mainlandC. rutilusdawsoni or the northeasternSiberian C. rutitusjochetsoni Allen; again, in this respect,it is analogousto the St. LawrenceIsland tundravole. Cranialdifferences, how- ever,are not sufficientto distinguishit specificalIy. The St. LawrenceIsland form is ratherpaIe dorsally,but in paleness it does not approachsome of the centralAsiatic races. C. rutilus albiventer is white ventralIy. In the same local populationsof C. rutilus dauJsoni,in- dividualsmay be eitherwhite or buffy ventrally. Microtusoeconomus innuitus Merriam. Tundra vole. Tundravole populationshad attaineda high densityby the summerof 1949. This abundanceof voIespersisted at least through 1951. Only winter observationswere made during 1952, so that any accurateevaluation of the statusof this animalcould not be made. About 600 specimensof this vole were obtained,of which 585 were used in parasitestudies (Rausch, 1952a). Merriam(1900; p. 21) describedthis vole on the basis of 12 skulls taken from food pelIetsregurgitated by owls or jaegers. It was recognizedby Zim- mermann(1942) as a subspeciesof M. oeconomusBlasius. Insofar as the writeris aware,this vole has not been studiedin detail exceptas mentioned above. Some data on size were recordedon a seriesof 84 individualscollected duringAugust, 1950. Of these, 23 femalesranged in weight from 60 to 96 grams(av. 71 grams), and 12 malesranged from 60 to 91 grams(av. 75.4). As an exampleof adult externaldimensions, a male collectedApril 23, 1950, weighing84.5 grams,measured: Total length, 190 mm.; tail, 43 mm.; hind foot length, 25 mm. A 60-gram female,collected the same date, measured: Total length, 172 mm.; tail, 42 mm.; hind foot, 23 mm. Skull measurements of ten adultvoles included in Table IV.

- TABLE IV Cranial measurementsof Microtus oeconomus innuitus. (in mi11imeters)

Condylo- Zygo- Inter- Length Lamb- Maxillary Weight basal matic orbital palatal Nasal doidal tooth row Sex (grams) length width width foramen length width length f 96 30.9 17.8 4.1 5.4 8.8 13.6 7 82 30.5 17.8 4.3 5.5 9 13.3 7 72 30.3 18.2 4.2 5.8 9 13.9 7.2 75 29.9 17.8 4.3 5.4 8.7 13.6 7 60 28.9 16.4 4.1 5.1 8 12.5 6.8 70 28.6 17 4.3 5.2 8.5 12.7 6.8 m 86 32 18.9 4.4 5.8 9.6 14.6 6.9 78 31.8 18 4.5 4.6 8.7 14.5 7.3 over 60 30.5 17.1 4.4 5.4 9 13.6 6.7 80 30.4 18 4.3 4.6 9 13.7 6.8 65 29.4 16.3 4.6 5 8.5 13 6.9 68 29.3 16.8 4.2 3.7 8.3 13.1 6.7 Average f 29.8 17.5 4.2 5.4 7.5 13.3 6.9 Average m 30.6 17.5 4.4 4.1 8.9 13.8 6.9 Rausch in MURRELET (May-August 1953) 34(2).

May-August,1 953 LAND MAMMALS OF ST. LAWRENCE ISLAND 26 Acknowledgements This opportunityis taken to thank the following personswho have aidedin makingthis workpossible: Dr. David H. Johnson,Division of Mam- mals, U. S. NationalMuseum, and Dr. CharlesP. Lyman,Museum of Com- parativeZoology, HarvardCollege, providedPalaearctic fox material;Dr. FrankPitelka, Museum of VertebrateZoology, University of California,loaned the specimensof Sorex Jacksoni;Mr. E. L. Schiller,of this laboratory,has donemuch of the fieIdwork on St. LawrenceIsland, and is responsiblefor the collectionof much of the material;Miss ReggieV. Sacressen,of this labora- tory, providedmuch technicalassistance; Mr. EdwardS. Weiss, chief of the Epidemiologyand Biometry Branch at this Center, advised regardingthe statisticalanalysis of the arcticfox data. The cooperationof many of the St. LawrenceIsland Eskimo is also gratefulyacknowledged. Animal-borneDisease Branch, Arctic Health ResearchCenter, Public Health Service,Dept. of Health, Educationand Welfare,Anchorage, Alaska.

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